problem about System.loadLibrary and object's address

[吴廷鹏 <wu...@gmail.com>]

Hi, all,
when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?

Another question, I read the implementation code of Object.clone method in Object_generic.cpp.

jobject object_clone(JNIEnv *jenv, jobject jobj)
{
    ObjectHandle h = (ObjectHandle) jobj;

    //aquire the target address and assign it to variable named result

    memcpy(result, h->object, size);

}
According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?  

Thanks,
tingpeng

Re: problem about System.loadLibrary and object's address

[Mikhail Fursov <mi...@gmail.com>]

BTW in JIT we have escape analysis optimization and if JIT can prove that an
object is not escaped from a method it can replace the object with a set of
local variables. Note that with aggressive inlining and profile guided
devirtualization the scope for this optimization is wider than the scope of
an original Java method.
JIT can scalarize an object even if the object is escaped. In this case
object is created and initialized right before the place it escapes.

An additional JIT-GC interface with manual 'free' method call for an object
can be used as a separate feature on execution paths that are not hot enough
to use scalarizaton on them.


On 4/30/07, LvJimmy，Jing <fi...@gmail.com> wrote:
>
> <SNIP>
> >
> > Jimmy, it's possible to insert free() automatically in jitted code to
> > reclaim some short-lived objects. This can be a supplementary to the
> > GC, and probably improve the overall performance. Tingpeng had
> > previous discussions with me on this topic actually.
> >
>
> Sorry I don't know the context.
> So the short-lived objects you mentioned can be invoked both in the
> native code and java code? And, should this "free" register to GC to
> tell GC the object has been reclaimed? Or the alloc and free process
> can be totally un-known to GC?
> And do VM offer some API for these functions?
> Please tell me if I miss something :)
>
> I'm very interested in this free() as well, I'll follow this thread.
>
> > TingPeng, the runtime helper is a way in DRLVM for the VM to provide
> > JIT certain supports, e.g.,  exception throwing, etc.  One of the
> > important usages of runtime helper is to provide a way of fast native
> > method invocation. That is, when you know a native method never causes
> > GC, you probably can use a runtime helper for JIT to generate code to
> > invoke this native method directly without going through the JNI
> > stuff. This makes native call fast.
> >
> > You can find runtime helper code in jit_runtime_support related files.
> > Please go search VM_RT_AASTORE in vm source code, you will see in
> > vmcore/src/util/ia32/base/jit_runtime_support_ia32.cpp how aastore can
> > implemented in native code to support JIT.    VM_RT_GC_HEAP_WRITE_REF
> > is an example for write barrier native implementation
> > gc_heap_slot_write_ref().
> >
> > Please let me know if you have any further questions.
> >
> > Thanks. xiaofeng
> >
> <SNIP>
>
>
> --
>
> Best Regards!
>
> Jimmy, Jing Lv
> China Software Development Lab, IBM
>



-- 
Mikhail Fursov

Re: problem about System.loadLibrary and object's address

[LvJimmy，Jing <fi...@gmail.com>]

<SNIP>
>
> Jimmy, it's possible to insert free() automatically in jitted code to
> reclaim some short-lived objects. This can be a supplementary to the
> GC, and probably improve the overall performance. Tingpeng had
> previous discussions with me on this topic actually.
>

Sorry I don't know the context.
So the short-lived objects you mentioned can be invoked both in the
native code and java code? And, should this "free" register to GC to
tell GC the object has been reclaimed? Or the alloc and free process
can be totally un-known to GC?
And do VM offer some API for these functions?
Please tell me if I miss something :)

I'm very interested in this free() as well, I'll follow this thread.

> TingPeng, the runtime helper is a way in DRLVM for the VM to provide
> JIT certain supports, e.g.,  exception throwing, etc.  One of the
> important usages of runtime helper is to provide a way of fast native
> method invocation. That is, when you know a native method never causes
> GC, you probably can use a runtime helper for JIT to generate code to
> invoke this native method directly without going through the JNI
> stuff. This makes native call fast.
>
> You can find runtime helper code in jit_runtime_support related files.
> Please go search VM_RT_AASTORE in vm source code, you will see in
> vmcore/src/util/ia32/base/jit_runtime_support_ia32.cpp how aastore can
> implemented in native code to support JIT.    VM_RT_GC_HEAP_WRITE_REF
> is an example for write barrier native implementation
> gc_heap_slot_write_ref().
>
> Please let me know if you have any further questions.
>
> Thanks. xiaofeng
>
<SNIP>


-- 

Best Regards!

Jimmy, Jing Lv
China Software Development Lab, IBM

Re: problem about System.loadLibrary and object's address

[Tingpeng Wu <wu...@gmail.com>]

xiaofeng, I have two major problems which need to be solved currently.
1. In my computer, Drlvm's java.exe couldn't run the java program which has loadLibrary call. I don't know whether it is for drlvm's reason or not. I don't know if others can run it correctly. It is a troublesome matter for me. 
2. Is it proper to use MyRuntime which was refered yesterday to support the free(obj) in the early work which is lack of support of JIT? I planned to verify it by an test program. But for above reason, I couldn't go on now.

Thanks,
tingpeng
  
----- Original Message ----- 
From: "Xiao-Feng Li" <xi...@gmail.com>
To: <de...@harmony.apache.org>
Sent: Monday, April 30, 2007 9:47 AM
Subject: Re: problem about System.loadLibrary and object's address


> Tingpeng, I think for first step test, you can use traditional JNI.
> The fast JNI is only for performance here.
> 
> Thanks,
> xiaofeng
> 
> On 4/29/07, Tingpeng Wu <wu...@gmail.com> wrote:
>> xiaofeng, very thank you for your help and valuable time. I will try your suggestion next.
>> ----- Original Message -----
>> From: "Xiao-Feng Li" <xi...@gmail.com>
>> To: <de...@harmony.apache.org>
>> Sent: Sunday, April 29, 2007 8:36 PM
>> Subject: Re: problem about System.loadLibrary and object's address
>>
>>
>> > On 4/29/07, LvJimmy，Jing <fi...@gmail.com> wrote:
>> >> 2007/4/29, Tingpeng Wu <wu...@gmail.com>:
>> >> >
>> >> > ----- Original Message -----
>> >> > From: "LvJimmy，Jing" <fi...@gmail.com>
>> >> > To: <de...@harmony.apache.org>
>> >> > Sent: Sunday, April 29, 2007 5:24 PM
>> >> > Subject: Re: problem about System.loadLibrary and object's address
>> >> >
>> >> >
>> >> > > 2007/4/29, Tingpeng Wu <wu...@gmail.com>:
>> >> > >> Hi, xiaofeng,
>> >> > >>
>> >> > >> 1. I also feel very unnatural to call it through MyRuntime class, but I don't know how to call it directly. Since drlvm needs HotSpot to help it to compile the java source code, if I don't call it though an instance, the HotSpot couldn't distinguish it. If I let the Jit to add the free() call in a future time, I will not need it any more.
>> >> > >>
>> >> > >
>> >> > > :) Java static method can be called as SomeClass.StaticMethod, so your
>> >> > > program can be written as (it is nothing related with compiler)
>> >> > > public static void main(String[] args)
>> >> > > {
>> >> > >    set(10);
>> >> > >    System.out.println(get());
>> >> > > }
>> >> > >
>> >> >
>> >> > >> 2. I added an method named "unsigned int get_object_addr(jobject jobj)" in object_handle.cpp to return the address of jobj . I can call it directly to get the object address in free() method. Since I could not assure whether it can get the right address, so I add the get_obj_addr() for test purpose. I will delete it if it can work corredtly.
>> >> > >>
>> >> > >
>> >> > > Ah, I don't catch well here. Why do you need a free() function here?
>> >> > > If you alloc a java object (no matter in java or native), you can just
>> >> > > leave it alone and let GC do everything for you. Free() is too c-style
>> >> > > for Java developer :)
>> >> > > In the other way, if you want to alloc some memory for other use, for
>> >> > > an example, char array in c/c++, you can just keep its address(you can
>> >> > > keep a jlong as void* ) and free it at last(you'd better free in this
>> >> > > case or you'll get memory leak). It is such easier to keep/pass a
>> >> > > jlong value than jobject handle.
>> >> > >
>> >> > My thesis is to redesign the heap layout, and provide the free() method to support reclaiming the object explicitly. Then in jit module, I will add some analysis to insert some free call to reclaim the dead object in advance. The purpose is to try to improve the efficiency of program's execution.
>> >> >
>> >>
>> >> Got it, I remember we've already discussed this problem (free() in
>> >> java) and IIRC, some expert mark this problem as "mission impossible"
>> >> ... :)
>> >> However study something about GC may benefit your thesis. :)
>> >
>> > Jimmy, it's possible to insert free() automatically in jitted code to
>> > reclaim some short-lived objects. This can be a supplementary to the
>> > GC, and probably improve the overall performance. Tingpeng had
>> > previous discussions with me on this topic actually.
>> >
>> > TingPeng, the runtime helper is a way in DRLVM for the VM to provide
>> > JIT certain supports, e.g.,  exception throwing, etc.  One of the
>> > important usages of runtime helper is to provide a way of fast native
>> > method invocation. That is, when you know a native method never causes
>> > GC, you probably can use a runtime helper for JIT to generate code to
>> > invoke this native method directly without going through the JNI
>> > stuff. This makes native call fast.
>> >
>> > You can find runtime helper code in jit_runtime_support related files.
>> > Please go search VM_RT_AASTORE in vm source code, you will see in
>> > vmcore/src/util/ia32/base/jit_runtime_support_ia32.cpp how aastore can
>> > implemented in native code to support JIT.    VM_RT_GC_HEAP_WRITE_REF
>> > is an example for write barrier native implementation
>> > gc_heap_slot_write_ref().
>> >
>> > Please let me know if you have any further questions.
>> >
>> > Thanks. xiaofeng
>> >
>> >> > >
>> >> > >> 3. Another quesetion: where is runtime helper you speak of? I am afraid I need do some investigation on it.
>> >> > >>
>> >> > >> Thanks,
>> >> > >> tingpeng
>> >> > >> ----- Original Message -----
>> >> > >> From: "Xiao-Feng Li" <xi...@gmail.com>
>> >> > >> To: <de...@harmony.apache.org>
>> >> > >> Sent: Sunday, April 29, 2007 4:05 PM
>> >> > >> Subject: Re: problem about System.loadLibrary and object's address
>> >> > >>
>> >> > >>
>> >> > >> > Tingpeng,
>> >> > >> >
>> >> > >> > 1. Your native is static native, why do you call it through an instance?
>> >> > >> > 2. You probably need to use runtime helper for the object direct free
>> >> > >> > in Java app, because the default JNI call path will save the object
>> >> > >> > handle (and passes the reference address as a root entry during GC
>> >> > >> > enumeration). For your purpose, there is no GC happening in free(),
>> >> > >> > so it probably works with a stale object reference (freed) in the
>> >> > >> > object handle.
>> >> > >> > 3. You can use free() directly to retrieve its object address from the
>> >> > >> > handle. Why do you need the get_obj_addr() method?
>> >> > >> >
>> >> > >> > Thanks,
>> >> > >> > xiaofeng
>> >> > >> >
>> >> > >> > On 4/29/07, Tingpeng Wu <wu...@gmail.com> wrote:
>> >> > >> >> Thanks, xiaofeng,
>> >> > >> >> My test program is simple as follows:
>> >> > >> >>
>> >> > >> >> public class JNItest
>> >> > >> >>
>> >> > >> >> {
>> >> > >> >>
>> >> > >> >> static
>> >> > >> >>
>> >> > >> >> {
>> >> > >> >>
>> >> > >> >> System.loadLibrary("goodluck");
>> >> > >> >>
>> >> > >> >> }
>> >> > >> >>
>> >> > >> >>
>> >> > >> >>
>> >> > >> >> public native static int get();
>> >> > >> >>
>> >> > >> >> public native static void set(int i);
>> >> > >> >>
>> >> > >> >>
>> >> > >> >>
>> >> > >> >> public static void main(String[] args)
>> >> > >> >>
>> >> > >> >> {
>> >> > >> >>
>> >> > >> >> JNItest test = new JNItest();
>> >> > >> >>
>> >> > >> >> test.set(10);
>> >> > >> >>
>> >> > >> >> System.out.println(test.get());
>> >> > >> >>
>> >> > >> >> }
>> >> > >> >>
>> >> > >> >> }
>> >> > >> >>
>> >> > >> >> Then I use javah to produce JNItest.h and implement two method in JNItest.cpp. Then use them to build goodluck.dll. I use the latest verson of drlvm to test it, there is still an error which reports "Vm launcher meets error and needs shut up (this is translated from chinese)".
>> >> > >> >>
>> >> > >> >> The reason I asked the second problem is I want to get the address of obj in java to support the reclaimation. I plan to
>> >> > >> >> MyRuntime class, which has a native method,
>> >> > >> >> My thought now is as follows:
>> >> > >> >> 1. provide a new class named MyRuntime which has two native methods.
>> >> > >> >>     class MyRuntime
>> >> > >> >>     {
>> >> > >> >>          static
>> >> > >> >>          {
>> >> > >> >>               System.loadLibrary("runtime");
>> >> > >> >>          }
>> >> > >> >>
>> >> > >> >>         //public native static void alloc(……);
>> >> > >> >>
>> >> > >> >>          public native static void get_obj_addr(Object obj);
>> >> > >> >>
>> >> > >> >>           //public native static void free(Object obj);
>> >> > >> >>     }
>> >> > >> >>
>> >> > >> >> 2.    export the get_object_addr(jobject jobj) in vmcore to support MyRuntime.get_obj_addr(Object obj)
>> >> > >> >> 3.    export the free(unsigned size, void* address) in gc to support MyRuntime.free(Object obj)
>> >> > >> >> 4.    if above is right, I can call MyRuntime.free(obj) in java method.
>> >> > >> >>
>> >> > >> >>
>> >> > >> >>
>> >> > >> >> Is it feasible to get address that way to support the reclaimation method?
>> >> > >> >>
>> >> > >> >> Thanks,
>> >> > >> >> tingpeng
>> >> > >> >>
>> >> > >> >> ----- Original Message -----
>> >> > >> >> From: "Xiao-Feng Li" <xi...@gmail.com>
>> >> > >> >> To: <de...@harmony.apache.org>
>> >> > >> >> Sent: Sunday, April 29, 2007 11:06 AM
>> >> > >> >> Subject: Re: problem about System.loadLibrary and object's address
>> >> > >> >>
>> >> > >> >>
>> >> > >> >> > Tingpeng, can you post your program if there is no legal issue? (e.g.,
>> >> > >> >> > open a JIRA issue and attach your code there).
>> >> > >> >> >
>> >> > >> >> > For your second question, itis pretty the core part of JVM native
>> >> > >> >> > interface design. Yes, the handle is used to access Java object
>> >> > >> >> > indirectly. The idea is to support object movement during GC, then the
>> >> > >> >> > real new address of the same object can be stored to the handle. It's
>> >> > >> >> > not supposed to be used everywhere in the JVM, because that may break
>> >> > >> >> > the protocol of JNI, causing GC to fail to update the object new
>> >> > >> >> > address, e.g., if it is put into a register by your C compiler. You
>> >> > >> >> > can access it in two ways: either always use JNI interface, or
>> >> > >> >> > guarantee there is GC happening when you access it.
>> >> > >> >> >
>> >> > >> >> > Thanks,
>> >> > >> >> > xiaofeng
>> >> > >> >> >
>> >> > >> >> > On 4/29/07, 吴廷鹏 <wu...@gmail.com> wrote:
>> >> > >> >> >> Hi, all,
>> >> > >> >> >> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
>> >> > >> >> >>
>> >> > >> >> >> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
>> >> > >> >> >>
>> >> > >> >> >> jobject object_clone(JNIEnv *jenv, jobject jobj)
>> >> > >> >> >> {
>> >> > >> >> >>     ObjectHandle h = (ObjectHandle) jobj;
>> >> > >> >> >>
>> >> > >> >> >>     //aquire the target address and assign it to variable named result
>> >> > >> >> >>
>> >> > >> >> >>     memcpy(result, h->object, size);
>> >> > >> >> >>
>> >> > >> >> >> }
>> >> > >> >> >> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
>> >> > >> >> >>
>> >> > >> >> >> Thanks,
>> >> > >> >> >> tingpeng
>> >> > >> >> >>
>> >> > >> >> >
>> >> > >> >> >
>> >> > >> >> > --
>> >> > >> >> > http://xiao-feng.blogspot.com
>> >> > >> >> >
>> >> > >> >
>> >> > >> >
>> >> > >> > --
>> >> > >> > http://xiao-feng.blogspot.com
>> >> > >> >
>> >> > >
>> >> > >
>> >> > > --
>> >> > >
>> >> > > Best Regards!
>> >> > >
>> >> > > Jimmy, Jing Lv
>> >> > > China Software Development Lab, IBM
>> >> > >
>> >>
>> >>
>> >> --
>> >>
>> >> Best Regards!
>> >>
>> >> Jimmy, Jing Lv
>> >> China Software Development Lab, IBM
>> >>
>> >
>> >
>> > --
>> > http://xiao-feng.blogspot.com
>> >
> 
> 
> -- 
> http://xiao-feng.blogspot.com
>

Re: problem about System.loadLibrary and object's address

[Xiao-Feng Li <xi...@gmail.com>]

Tingpeng, I think for first step test, you can use traditional JNI.
The fast JNI is only for performance here.

Thanks,
xiaofeng

On 4/29/07, Tingpeng Wu <wu...@gmail.com> wrote:
> xiaofeng, very thank you for your help and valuable time. I will try your suggestion next.
> ----- Original Message -----
> From: "Xiao-Feng Li" <xi...@gmail.com>
> To: <de...@harmony.apache.org>
> Sent: Sunday, April 29, 2007 8:36 PM
> Subject: Re: problem about System.loadLibrary and object's address
>
>
> > On 4/29/07, LvJimmy，Jing <fi...@gmail.com> wrote:
> >> 2007/4/29, Tingpeng Wu <wu...@gmail.com>:
> >> >
> >> > ----- Original Message -----
> >> > From: "LvJimmy，Jing" <fi...@gmail.com>
> >> > To: <de...@harmony.apache.org>
> >> > Sent: Sunday, April 29, 2007 5:24 PM
> >> > Subject: Re: problem about System.loadLibrary and object's address
> >> >
> >> >
> >> > > 2007/4/29, Tingpeng Wu <wu...@gmail.com>:
> >> > >> Hi, xiaofeng,
> >> > >>
> >> > >> 1. I also feel very unnatural to call it through MyRuntime class, but I don't know how to call it directly. Since drlvm needs HotSpot to help it to compile the java source code, if I don't call it though an instance, the HotSpot couldn't distinguish it. If I let the Jit to add the free() call in a future time, I will not need it any more.
> >> > >>
> >> > >
> >> > > :) Java static method can be called as SomeClass.StaticMethod, so your
> >> > > program can be written as (it is nothing related with compiler)
> >> > > public static void main(String[] args)
> >> > > {
> >> > >    set(10);
> >> > >    System.out.println(get());
> >> > > }
> >> > >
> >> >
> >> > >> 2. I added an method named "unsigned int get_object_addr(jobject jobj)" in object_handle.cpp to return the address of jobj . I can call it directly to get the object address in free() method. Since I could not assure whether it can get the right address, so I add the get_obj_addr() for test purpose. I will delete it if it can work corredtly.
> >> > >>
> >> > >
> >> > > Ah, I don't catch well here. Why do you need a free() function here?
> >> > > If you alloc a java object (no matter in java or native), you can just
> >> > > leave it alone and let GC do everything for you. Free() is too c-style
> >> > > for Java developer :)
> >> > > In the other way, if you want to alloc some memory for other use, for
> >> > > an example, char array in c/c++, you can just keep its address(you can
> >> > > keep a jlong as void* ) and free it at last(you'd better free in this
> >> > > case or you'll get memory leak). It is such easier to keep/pass a
> >> > > jlong value than jobject handle.
> >> > >
> >> > My thesis is to redesign the heap layout, and provide the free() method to support reclaiming the object explicitly. Then in jit module, I will add some analysis to insert some free call to reclaim the dead object in advance. The purpose is to try to improve the efficiency of program's execution.
> >> >
> >>
> >> Got it, I remember we've already discussed this problem (free() in
> >> java) and IIRC, some expert mark this problem as "mission impossible"
> >> ... :)
> >> However study something about GC may benefit your thesis. :)
> >
> > Jimmy, it's possible to insert free() automatically in jitted code to
> > reclaim some short-lived objects. This can be a supplementary to the
> > GC, and probably improve the overall performance. Tingpeng had
> > previous discussions with me on this topic actually.
> >
> > TingPeng, the runtime helper is a way in DRLVM for the VM to provide
> > JIT certain supports, e.g.,  exception throwing, etc.  One of the
> > important usages of runtime helper is to provide a way of fast native
> > method invocation. That is, when you know a native method never causes
> > GC, you probably can use a runtime helper for JIT to generate code to
> > invoke this native method directly without going through the JNI
> > stuff. This makes native call fast.
> >
> > You can find runtime helper code in jit_runtime_support related files.
> > Please go search VM_RT_AASTORE in vm source code, you will see in
> > vmcore/src/util/ia32/base/jit_runtime_support_ia32.cpp how aastore can
> > implemented in native code to support JIT.    VM_RT_GC_HEAP_WRITE_REF
> > is an example for write barrier native implementation
> > gc_heap_slot_write_ref().
> >
> > Please let me know if you have any further questions.
> >
> > Thanks. xiaofeng
> >
> >> > >
> >> > >> 3. Another quesetion: where is runtime helper you speak of? I am afraid I need do some investigation on it.
> >> > >>
> >> > >> Thanks,
> >> > >> tingpeng
> >> > >> ----- Original Message -----
> >> > >> From: "Xiao-Feng Li" <xi...@gmail.com>
> >> > >> To: <de...@harmony.apache.org>
> >> > >> Sent: Sunday, April 29, 2007 4:05 PM
> >> > >> Subject: Re: problem about System.loadLibrary and object's address
> >> > >>
> >> > >>
> >> > >> > Tingpeng,
> >> > >> >
> >> > >> > 1. Your native is static native, why do you call it through an instance?
> >> > >> > 2. You probably need to use runtime helper for the object direct free
> >> > >> > in Java app, because the default JNI call path will save the object
> >> > >> > handle (and passes the reference address as a root entry during GC
> >> > >> > enumeration). For your purpose, there is no GC happening in free(),
> >> > >> > so it probably works with a stale object reference (freed) in the
> >> > >> > object handle.
> >> > >> > 3. You can use free() directly to retrieve its object address from the
> >> > >> > handle. Why do you need the get_obj_addr() method?
> >> > >> >
> >> > >> > Thanks,
> >> > >> > xiaofeng
> >> > >> >
> >> > >> > On 4/29/07, Tingpeng Wu <wu...@gmail.com> wrote:
> >> > >> >> Thanks, xiaofeng,
> >> > >> >> My test program is simple as follows:
> >> > >> >>
> >> > >> >> public class JNItest
> >> > >> >>
> >> > >> >> {
> >> > >> >>
> >> > >> >> static
> >> > >> >>
> >> > >> >> {
> >> > >> >>
> >> > >> >> System.loadLibrary("goodluck");
> >> > >> >>
> >> > >> >> }
> >> > >> >>
> >> > >> >>
> >> > >> >>
> >> > >> >> public native static int get();
> >> > >> >>
> >> > >> >> public native static void set(int i);
> >> > >> >>
> >> > >> >>
> >> > >> >>
> >> > >> >> public static void main(String[] args)
> >> > >> >>
> >> > >> >> {
> >> > >> >>
> >> > >> >> JNItest test = new JNItest();
> >> > >> >>
> >> > >> >> test.set(10);
> >> > >> >>
> >> > >> >> System.out.println(test.get());
> >> > >> >>
> >> > >> >> }
> >> > >> >>
> >> > >> >> }
> >> > >> >>
> >> > >> >> Then I use javah to produce JNItest.h and implement two method in JNItest.cpp. Then use them to build goodluck.dll. I use the latest verson of drlvm to test it, there is still an error which reports "Vm launcher meets error and needs shut up (this is translated from chinese)".
> >> > >> >>
> >> > >> >> The reason I asked the second problem is I want to get the address of obj in java to support the reclaimation. I plan to
> >> > >> >> MyRuntime class, which has a native method,
> >> > >> >> My thought now is as follows:
> >> > >> >> 1. provide a new class named MyRuntime which has two native methods.
> >> > >> >>     class MyRuntime
> >> > >> >>     {
> >> > >> >>          static
> >> > >> >>          {
> >> > >> >>               System.loadLibrary("runtime");
> >> > >> >>          }
> >> > >> >>
> >> > >> >>         //public native static void alloc(……);
> >> > >> >>
> >> > >> >>          public native static void get_obj_addr(Object obj);
> >> > >> >>
> >> > >> >>           //public native static void free(Object obj);
> >> > >> >>     }
> >> > >> >>
> >> > >> >> 2.    export the get_object_addr(jobject jobj) in vmcore to support MyRuntime.get_obj_addr(Object obj)
> >> > >> >> 3.    export the free(unsigned size, void* address) in gc to support MyRuntime.free(Object obj)
> >> > >> >> 4.    if above is right, I can call MyRuntime.free(obj) in java method.
> >> > >> >>
> >> > >> >>
> >> > >> >>
> >> > >> >> Is it feasible to get address that way to support the reclaimation method?
> >> > >> >>
> >> > >> >> Thanks,
> >> > >> >> tingpeng
> >> > >> >>
> >> > >> >> ----- Original Message -----
> >> > >> >> From: "Xiao-Feng Li" <xi...@gmail.com>
> >> > >> >> To: <de...@harmony.apache.org>
> >> > >> >> Sent: Sunday, April 29, 2007 11:06 AM
> >> > >> >> Subject: Re: problem about System.loadLibrary and object's address
> >> > >> >>
> >> > >> >>
> >> > >> >> > Tingpeng, can you post your program if there is no legal issue? (e.g.,
> >> > >> >> > open a JIRA issue and attach your code there).
> >> > >> >> >
> >> > >> >> > For your second question, itis pretty the core part of JVM native
> >> > >> >> > interface design. Yes, the handle is used to access Java object
> >> > >> >> > indirectly. The idea is to support object movement during GC, then the
> >> > >> >> > real new address of the same object can be stored to the handle. It's
> >> > >> >> > not supposed to be used everywhere in the JVM, because that may break
> >> > >> >> > the protocol of JNI, causing GC to fail to update the object new
> >> > >> >> > address, e.g., if it is put into a register by your C compiler. You
> >> > >> >> > can access it in two ways: either always use JNI interface, or
> >> > >> >> > guarantee there is GC happening when you access it.
> >> > >> >> >
> >> > >> >> > Thanks,
> >> > >> >> > xiaofeng
> >> > >> >> >
> >> > >> >> > On 4/29/07, 吴廷鹏 <wu...@gmail.com> wrote:
> >> > >> >> >> Hi, all,
> >> > >> >> >> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
> >> > >> >> >>
> >> > >> >> >> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
> >> > >> >> >>
> >> > >> >> >> jobject object_clone(JNIEnv *jenv, jobject jobj)
> >> > >> >> >> {
> >> > >> >> >>     ObjectHandle h = (ObjectHandle) jobj;
> >> > >> >> >>
> >> > >> >> >>     //aquire the target address and assign it to variable named result
> >> > >> >> >>
> >> > >> >> >>     memcpy(result, h->object, size);
> >> > >> >> >>
> >> > >> >> >> }
> >> > >> >> >> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
> >> > >> >> >>
> >> > >> >> >> Thanks,
> >> > >> >> >> tingpeng
> >> > >> >> >>
> >> > >> >> >
> >> > >> >> >
> >> > >> >> > --
> >> > >> >> > http://xiao-feng.blogspot.com
> >> > >> >> >
> >> > >> >
> >> > >> >
> >> > >> > --
> >> > >> > http://xiao-feng.blogspot.com
> >> > >> >
> >> > >
> >> > >
> >> > > --
> >> > >
> >> > > Best Regards!
> >> > >
> >> > > Jimmy, Jing Lv
> >> > > China Software Development Lab, IBM
> >> > >
> >>
> >>
> >> --
> >>
> >> Best Regards!
> >>
> >> Jimmy, Jing Lv
> >> China Software Development Lab, IBM
> >>
> >
> >
> > --
> > http://xiao-feng.blogspot.com
> >


-- 
http://xiao-feng.blogspot.com

Re: problem about System.loadLibrary and object's address

[Tingpeng Wu <wu...@gmail.com>]

xiaofeng, very thank you for your help and valuable time. I will try your suggestion next.
----- Original Message ----- 
From: "Xiao-Feng Li" <xi...@gmail.com>
To: <de...@harmony.apache.org>
Sent: Sunday, April 29, 2007 8:36 PM
Subject: Re: problem about System.loadLibrary and object's address


> On 4/29/07, LvJimmy，Jing <fi...@gmail.com> wrote:
>> 2007/4/29, Tingpeng Wu <wu...@gmail.com>:
>> >
>> > ----- Original Message -----
>> > From: "LvJimmy，Jing" <fi...@gmail.com>
>> > To: <de...@harmony.apache.org>
>> > Sent: Sunday, April 29, 2007 5:24 PM
>> > Subject: Re: problem about System.loadLibrary and object's address
>> >
>> >
>> > > 2007/4/29, Tingpeng Wu <wu...@gmail.com>:
>> > >> Hi, xiaofeng,
>> > >>
>> > >> 1. I also feel very unnatural to call it through MyRuntime class, but I don't know how to call it directly. Since drlvm needs HotSpot to help it to compile the java source code, if I don't call it though an instance, the HotSpot couldn't distinguish it. If I let the Jit to add the free() call in a future time, I will not need it any more.
>> > >>
>> > >
>> > > :) Java static method can be called as SomeClass.StaticMethod, so your
>> > > program can be written as (it is nothing related with compiler)
>> > > public static void main(String[] args)
>> > > {
>> > >    set(10);
>> > >    System.out.println(get());
>> > > }
>> > >
>> >
>> > >> 2. I added an method named "unsigned int get_object_addr(jobject jobj)" in object_handle.cpp to return the address of jobj . I can call it directly to get the object address in free() method. Since I could not assure whether it can get the right address, so I add the get_obj_addr() for test purpose. I will delete it if it can work corredtly.
>> > >>
>> > >
>> > > Ah, I don't catch well here. Why do you need a free() function here?
>> > > If you alloc a java object (no matter in java or native), you can just
>> > > leave it alone and let GC do everything for you. Free() is too c-style
>> > > for Java developer :)
>> > > In the other way, if you want to alloc some memory for other use, for
>> > > an example, char array in c/c++, you can just keep its address(you can
>> > > keep a jlong as void* ) and free it at last(you'd better free in this
>> > > case or you'll get memory leak). It is such easier to keep/pass a
>> > > jlong value than jobject handle.
>> > >
>> > My thesis is to redesign the heap layout, and provide the free() method to support reclaiming the object explicitly. Then in jit module, I will add some analysis to insert some free call to reclaim the dead object in advance. The purpose is to try to improve the efficiency of program's execution.
>> >
>>
>> Got it, I remember we've already discussed this problem (free() in
>> java) and IIRC, some expert mark this problem as "mission impossible"
>> ... :)
>> However study something about GC may benefit your thesis. :)
> 
> Jimmy, it's possible to insert free() automatically in jitted code to
> reclaim some short-lived objects. This can be a supplementary to the
> GC, and probably improve the overall performance. Tingpeng had
> previous discussions with me on this topic actually.
> 
> TingPeng, the runtime helper is a way in DRLVM for the VM to provide
> JIT certain supports, e.g.,  exception throwing, etc.  One of the
> important usages of runtime helper is to provide a way of fast native
> method invocation. That is, when you know a native method never causes
> GC, you probably can use a runtime helper for JIT to generate code to
> invoke this native method directly without going through the JNI
> stuff. This makes native call fast.
> 
> You can find runtime helper code in jit_runtime_support related files.
> Please go search VM_RT_AASTORE in vm source code, you will see in
> vmcore/src/util/ia32/base/jit_runtime_support_ia32.cpp how aastore can
> implemented in native code to support JIT.    VM_RT_GC_HEAP_WRITE_REF
> is an example for write barrier native implementation
> gc_heap_slot_write_ref().
> 
> Please let me know if you have any further questions.
> 
> Thanks. xiaofeng
> 
>> > >
>> > >> 3. Another quesetion: where is runtime helper you speak of? I am afraid I need do some investigation on it.
>> > >>
>> > >> Thanks,
>> > >> tingpeng
>> > >> ----- Original Message -----
>> > >> From: "Xiao-Feng Li" <xi...@gmail.com>
>> > >> To: <de...@harmony.apache.org>
>> > >> Sent: Sunday, April 29, 2007 4:05 PM
>> > >> Subject: Re: problem about System.loadLibrary and object's address
>> > >>
>> > >>
>> > >> > Tingpeng,
>> > >> >
>> > >> > 1. Your native is static native, why do you call it through an instance?
>> > >> > 2. You probably need to use runtime helper for the object direct free
>> > >> > in Java app, because the default JNI call path will save the object
>> > >> > handle (and passes the reference address as a root entry during GC
>> > >> > enumeration). For your purpose, there is no GC happening in free(),
>> > >> > so it probably works with a stale object reference (freed) in the
>> > >> > object handle.
>> > >> > 3. You can use free() directly to retrieve its object address from the
>> > >> > handle. Why do you need the get_obj_addr() method?
>> > >> >
>> > >> > Thanks,
>> > >> > xiaofeng
>> > >> >
>> > >> > On 4/29/07, Tingpeng Wu <wu...@gmail.com> wrote:
>> > >> >> Thanks, xiaofeng,
>> > >> >> My test program is simple as follows:
>> > >> >>
>> > >> >> public class JNItest
>> > >> >>
>> > >> >> {
>> > >> >>
>> > >> >> static
>> > >> >>
>> > >> >> {
>> > >> >>
>> > >> >> System.loadLibrary("goodluck");
>> > >> >>
>> > >> >> }
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> public native static int get();
>> > >> >>
>> > >> >> public native static void set(int i);
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> public static void main(String[] args)
>> > >> >>
>> > >> >> {
>> > >> >>
>> > >> >> JNItest test = new JNItest();
>> > >> >>
>> > >> >> test.set(10);
>> > >> >>
>> > >> >> System.out.println(test.get());
>> > >> >>
>> > >> >> }
>> > >> >>
>> > >> >> }
>> > >> >>
>> > >> >> Then I use javah to produce JNItest.h and implement two method in JNItest.cpp. Then use them to build goodluck.dll. I use the latest verson of drlvm to test it, there is still an error which reports "Vm launcher meets error and needs shut up (this is translated from chinese)".
>> > >> >>
>> > >> >> The reason I asked the second problem is I want to get the address of obj in java to support the reclaimation. I plan to
>> > >> >> MyRuntime class, which has a native method,
>> > >> >> My thought now is as follows:
>> > >> >> 1. provide a new class named MyRuntime which has two native methods.
>> > >> >>     class MyRuntime
>> > >> >>     {
>> > >> >>          static
>> > >> >>          {
>> > >> >>               System.loadLibrary("runtime");
>> > >> >>          }
>> > >> >>
>> > >> >>         //public native static void alloc(……);
>> > >> >>
>> > >> >>          public native static void get_obj_addr(Object obj);
>> > >> >>
>> > >> >>           //public native static void free(Object obj);
>> > >> >>     }
>> > >> >>
>> > >> >> 2.    export the get_object_addr(jobject jobj) in vmcore to support MyRuntime.get_obj_addr(Object obj)
>> > >> >> 3.    export the free(unsigned size, void* address) in gc to support MyRuntime.free(Object obj)
>> > >> >> 4.    if above is right, I can call MyRuntime.free(obj) in java method.
>> > >> >>
>> > >> >>
>> > >> >>
>> > >> >> Is it feasible to get address that way to support the reclaimation method?
>> > >> >>
>> > >> >> Thanks,
>> > >> >> tingpeng
>> > >> >>
>> > >> >> ----- Original Message -----
>> > >> >> From: "Xiao-Feng Li" <xi...@gmail.com>
>> > >> >> To: <de...@harmony.apache.org>
>> > >> >> Sent: Sunday, April 29, 2007 11:06 AM
>> > >> >> Subject: Re: problem about System.loadLibrary and object's address
>> > >> >>
>> > >> >>
>> > >> >> > Tingpeng, can you post your program if there is no legal issue? (e.g.,
>> > >> >> > open a JIRA issue and attach your code there).
>> > >> >> >
>> > >> >> > For your second question, itis pretty the core part of JVM native
>> > >> >> > interface design. Yes, the handle is used to access Java object
>> > >> >> > indirectly. The idea is to support object movement during GC, then the
>> > >> >> > real new address of the same object can be stored to the handle. It's
>> > >> >> > not supposed to be used everywhere in the JVM, because that may break
>> > >> >> > the protocol of JNI, causing GC to fail to update the object new
>> > >> >> > address, e.g., if it is put into a register by your C compiler. You
>> > >> >> > can access it in two ways: either always use JNI interface, or
>> > >> >> > guarantee there is GC happening when you access it.
>> > >> >> >
>> > >> >> > Thanks,
>> > >> >> > xiaofeng
>> > >> >> >
>> > >> >> > On 4/29/07, 吴廷鹏 <wu...@gmail.com> wrote:
>> > >> >> >> Hi, all,
>> > >> >> >> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
>> > >> >> >>
>> > >> >> >> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
>> > >> >> >>
>> > >> >> >> jobject object_clone(JNIEnv *jenv, jobject jobj)
>> > >> >> >> {
>> > >> >> >>     ObjectHandle h = (ObjectHandle) jobj;
>> > >> >> >>
>> > >> >> >>     //aquire the target address and assign it to variable named result
>> > >> >> >>
>> > >> >> >>     memcpy(result, h->object, size);
>> > >> >> >>
>> > >> >> >> }
>> > >> >> >> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
>> > >> >> >>
>> > >> >> >> Thanks,
>> > >> >> >> tingpeng
>> > >> >> >>
>> > >> >> >
>> > >> >> >
>> > >> >> > --
>> > >> >> > http://xiao-feng.blogspot.com
>> > >> >> >
>> > >> >
>> > >> >
>> > >> > --
>> > >> > http://xiao-feng.blogspot.com
>> > >> >
>> > >
>> > >
>> > > --
>> > >
>> > > Best Regards!
>> > >
>> > > Jimmy, Jing Lv
>> > > China Software Development Lab, IBM
>> > >
>>
>>
>> --
>>
>> Best Regards!
>>
>> Jimmy, Jing Lv
>> China Software Development Lab, IBM
>>
> 
> 
> -- 
> http://xiao-feng.blogspot.com
>

Re: problem about System.loadLibrary and object's address

[Xiao-Feng Li <xi...@gmail.com>]

On 4/29/07, LvJimmy，Jing <fi...@gmail.com> wrote:
> 2007/4/29, Tingpeng Wu <wu...@gmail.com>:
> >
> > ----- Original Message -----
> > From: "LvJimmy，Jing" <fi...@gmail.com>
> > To: <de...@harmony.apache.org>
> > Sent: Sunday, April 29, 2007 5:24 PM
> > Subject: Re: problem about System.loadLibrary and object's address
> >
> >
> > > 2007/4/29, Tingpeng Wu <wu...@gmail.com>:
> > >> Hi, xiaofeng,
> > >>
> > >> 1. I also feel very unnatural to call it through MyRuntime class, but I don't know how to call it directly. Since drlvm needs HotSpot to help it to compile the java source code, if I don't call it though an instance, the HotSpot couldn't distinguish it. If I let the Jit to add the free() call in a future time, I will not need it any more.
> > >>
> > >
> > > :) Java static method can be called as SomeClass.StaticMethod, so your
> > > program can be written as (it is nothing related with compiler)
> > > public static void main(String[] args)
> > > {
> > >    set(10);
> > >    System.out.println(get());
> > > }
> > >
> >
> > >> 2. I added an method named "unsigned int get_object_addr(jobject jobj)" in object_handle.cpp to return the address of jobj . I can call it directly to get the object address in free() method. Since I could not assure whether it can get the right address, so I add the get_obj_addr() for test purpose. I will delete it if it can work corredtly.
> > >>
> > >
> > > Ah, I don't catch well here. Why do you need a free() function here?
> > > If you alloc a java object (no matter in java or native), you can just
> > > leave it alone and let GC do everything for you. Free() is too c-style
> > > for Java developer :)
> > > In the other way, if you want to alloc some memory for other use, for
> > > an example, char array in c/c++, you can just keep its address(you can
> > > keep a jlong as void* ) and free it at last(you'd better free in this
> > > case or you'll get memory leak). It is such easier to keep/pass a
> > > jlong value than jobject handle.
> > >
> > My thesis is to redesign the heap layout, and provide the free() method to support reclaiming the object explicitly. Then in jit module, I will add some analysis to insert some free call to reclaim the dead object in advance. The purpose is to try to improve the efficiency of program's execution.
> >
>
> Got it, I remember we've already discussed this problem (free() in
> java) and IIRC, some expert mark this problem as "mission impossible"
> ... :)
> However study something about GC may benefit your thesis. :)

Jimmy, it's possible to insert free() automatically in jitted code to
reclaim some short-lived objects. This can be a supplementary to the
GC, and probably improve the overall performance. Tingpeng had
previous discussions with me on this topic actually.

TingPeng, the runtime helper is a way in DRLVM for the VM to provide
JIT certain supports, e.g.,  exception throwing, etc.  One of the
important usages of runtime helper is to provide a way of fast native
method invocation. That is, when you know a native method never causes
GC, you probably can use a runtime helper for JIT to generate code to
invoke this native method directly without going through the JNI
stuff. This makes native call fast.

You can find runtime helper code in jit_runtime_support related files.
Please go search VM_RT_AASTORE in vm source code, you will see in
vmcore/src/util/ia32/base/jit_runtime_support_ia32.cpp how aastore can
implemented in native code to support JIT.    VM_RT_GC_HEAP_WRITE_REF
is an example for write barrier native implementation
gc_heap_slot_write_ref().

Please let me know if you have any further questions.

Thanks. xiaofeng

> > >
> > >> 3. Another quesetion: where is runtime helper you speak of? I am afraid I need do some investigation on it.
> > >>
> > >> Thanks,
> > >> tingpeng
> > >> ----- Original Message -----
> > >> From: "Xiao-Feng Li" <xi...@gmail.com>
> > >> To: <de...@harmony.apache.org>
> > >> Sent: Sunday, April 29, 2007 4:05 PM
> > >> Subject: Re: problem about System.loadLibrary and object's address
> > >>
> > >>
> > >> > Tingpeng,
> > >> >
> > >> > 1. Your native is static native, why do you call it through an instance?
> > >> > 2. You probably need to use runtime helper for the object direct free
> > >> > in Java app, because the default JNI call path will save the object
> > >> > handle (and passes the reference address as a root entry during GC
> > >> > enumeration). For your purpose, there is no GC happening in free(),
> > >> > so it probably works with a stale object reference (freed) in the
> > >> > object handle.
> > >> > 3. You can use free() directly to retrieve its object address from the
> > >> > handle. Why do you need the get_obj_addr() method?
> > >> >
> > >> > Thanks,
> > >> > xiaofeng
> > >> >
> > >> > On 4/29/07, Tingpeng Wu <wu...@gmail.com> wrote:
> > >> >> Thanks, xiaofeng,
> > >> >> My test program is simple as follows:
> > >> >>
> > >> >> public class JNItest
> > >> >>
> > >> >> {
> > >> >>
> > >> >> static
> > >> >>
> > >> >> {
> > >> >>
> > >> >> System.loadLibrary("goodluck");
> > >> >>
> > >> >> }
> > >> >>
> > >> >>
> > >> >>
> > >> >> public native static int get();
> > >> >>
> > >> >> public native static void set(int i);
> > >> >>
> > >> >>
> > >> >>
> > >> >> public static void main(String[] args)
> > >> >>
> > >> >> {
> > >> >>
> > >> >> JNItest test = new JNItest();
> > >> >>
> > >> >> test.set(10);
> > >> >>
> > >> >> System.out.println(test.get());
> > >> >>
> > >> >> }
> > >> >>
> > >> >> }
> > >> >>
> > >> >> Then I use javah to produce JNItest.h and implement two method in JNItest.cpp. Then use them to build goodluck.dll. I use the latest verson of drlvm to test it, there is still an error which reports "Vm launcher meets error and needs shut up (this is translated from chinese)".
> > >> >>
> > >> >> The reason I asked the second problem is I want to get the address of obj in java to support the reclaimation. I plan to
> > >> >> MyRuntime class, which has a native method,
> > >> >> My thought now is as follows:
> > >> >> 1. provide a new class named MyRuntime which has two native methods.
> > >> >>     class MyRuntime
> > >> >>     {
> > >> >>          static
> > >> >>          {
> > >> >>               System.loadLibrary("runtime");
> > >> >>          }
> > >> >>
> > >> >>         //public native static void alloc(……);
> > >> >>
> > >> >>          public native static void get_obj_addr(Object obj);
> > >> >>
> > >> >>           //public native static void free(Object obj);
> > >> >>     }
> > >> >>
> > >> >> 2.    export the get_object_addr(jobject jobj) in vmcore to support MyRuntime.get_obj_addr(Object obj)
> > >> >> 3.    export the free(unsigned size, void* address) in gc to support MyRuntime.free(Object obj)
> > >> >> 4.    if above is right, I can call MyRuntime.free(obj) in java method.
> > >> >>
> > >> >>
> > >> >>
> > >> >> Is it feasible to get address that way to support the reclaimation method?
> > >> >>
> > >> >> Thanks,
> > >> >> tingpeng
> > >> >>
> > >> >> ----- Original Message -----
> > >> >> From: "Xiao-Feng Li" <xi...@gmail.com>
> > >> >> To: <de...@harmony.apache.org>
> > >> >> Sent: Sunday, April 29, 2007 11:06 AM
> > >> >> Subject: Re: problem about System.loadLibrary and object's address
> > >> >>
> > >> >>
> > >> >> > Tingpeng, can you post your program if there is no legal issue? (e.g.,
> > >> >> > open a JIRA issue and attach your code there).
> > >> >> >
> > >> >> > For your second question, itis pretty the core part of JVM native
> > >> >> > interface design. Yes, the handle is used to access Java object
> > >> >> > indirectly. The idea is to support object movement during GC, then the
> > >> >> > real new address of the same object can be stored to the handle. It's
> > >> >> > not supposed to be used everywhere in the JVM, because that may break
> > >> >> > the protocol of JNI, causing GC to fail to update the object new
> > >> >> > address, e.g., if it is put into a register by your C compiler. You
> > >> >> > can access it in two ways: either always use JNI interface, or
> > >> >> > guarantee there is GC happening when you access it.
> > >> >> >
> > >> >> > Thanks,
> > >> >> > xiaofeng
> > >> >> >
> > >> >> > On 4/29/07, 吴廷鹏 <wu...@gmail.com> wrote:
> > >> >> >> Hi, all,
> > >> >> >> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
> > >> >> >>
> > >> >> >> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
> > >> >> >>
> > >> >> >> jobject object_clone(JNIEnv *jenv, jobject jobj)
> > >> >> >> {
> > >> >> >>     ObjectHandle h = (ObjectHandle) jobj;
> > >> >> >>
> > >> >> >>     //aquire the target address and assign it to variable named result
> > >> >> >>
> > >> >> >>     memcpy(result, h->object, size);
> > >> >> >>
> > >> >> >> }
> > >> >> >> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
> > >> >> >>
> > >> >> >> Thanks,
> > >> >> >> tingpeng
> > >> >> >>
> > >> >> >
> > >> >> >
> > >> >> > --
> > >> >> > http://xiao-feng.blogspot.com
> > >> >> >
> > >> >
> > >> >
> > >> > --
> > >> > http://xiao-feng.blogspot.com
> > >> >
> > >
> > >
> > > --
> > >
> > > Best Regards!
> > >
> > > Jimmy, Jing Lv
> > > China Software Development Lab, IBM
> > >
>
>
> --
>
> Best Regards!
>
> Jimmy, Jing Lv
> China Software Development Lab, IBM
>


-- 
http://xiao-feng.blogspot.com

Re: problem about System.loadLibrary and object's address

[LvJimmy，Jing <fi...@gmail.com>]

2007/4/29, Tingpeng Wu <wu...@gmail.com>:
>
> ----- Original Message -----
> From: "LvJimmy，Jing" <fi...@gmail.com>
> To: <de...@harmony.apache.org>
> Sent: Sunday, April 29, 2007 5:24 PM
> Subject: Re: problem about System.loadLibrary and object's address
>
>
> > 2007/4/29, Tingpeng Wu <wu...@gmail.com>:
> >> Hi, xiaofeng,
> >>
> >> 1. I also feel very unnatural to call it through MyRuntime class, but I don't know how to call it directly. Since drlvm needs HotSpot to help it to compile the java source code, if I don't call it though an instance, the HotSpot couldn't distinguish it. If I let the Jit to add the free() call in a future time, I will not need it any more.
> >>
> >
> > :) Java static method can be called as SomeClass.StaticMethod, so your
> > program can be written as (it is nothing related with compiler)
> > public static void main(String[] args)
> > {
> >    set(10);
> >    System.out.println(get());
> > }
> >
>
> >> 2. I added an method named "unsigned int get_object_addr(jobject jobj)" in object_handle.cpp to return the address of jobj . I can call it directly to get the object address in free() method. Since I could not assure whether it can get the right address, so I add the get_obj_addr() for test purpose. I will delete it if it can work corredtly.
> >>
> >
> > Ah, I don't catch well here. Why do you need a free() function here?
> > If you alloc a java object (no matter in java or native), you can just
> > leave it alone and let GC do everything for you. Free() is too c-style
> > for Java developer :)
> > In the other way, if you want to alloc some memory for other use, for
> > an example, char array in c/c++, you can just keep its address(you can
> > keep a jlong as void* ) and free it at last(you'd better free in this
> > case or you'll get memory leak). It is such easier to keep/pass a
> > jlong value than jobject handle.
> >
> My thesis is to redesign the heap layout, and provide the free() method to support reclaiming the object explicitly. Then in jit module, I will add some analysis to insert some free call to reclaim the dead object in advance. The purpose is to try to improve the efficiency of program's execution.
>

Got it, I remember we've already discussed this problem (free() in
java) and IIRC, some expert mark this problem as "mission impossible"
... :)
However study something about GC may benefit your thesis. :)

> >
> >> 3. Another quesetion: where is runtime helper you speak of? I am afraid I need do some investigation on it.
> >>
> >> Thanks,
> >> tingpeng
> >> ----- Original Message -----
> >> From: "Xiao-Feng Li" <xi...@gmail.com>
> >> To: <de...@harmony.apache.org>
> >> Sent: Sunday, April 29, 2007 4:05 PM
> >> Subject: Re: problem about System.loadLibrary and object's address
> >>
> >>
> >> > Tingpeng,
> >> >
> >> > 1. Your native is static native, why do you call it through an instance?
> >> > 2. You probably need to use runtime helper for the object direct free
> >> > in Java app, because the default JNI call path will save the object
> >> > handle (and passes the reference address as a root entry during GC
> >> > enumeration). For your purpose, there is no GC happening in free(),
> >> > so it probably works with a stale object reference (freed) in the
> >> > object handle.
> >> > 3. You can use free() directly to retrieve its object address from the
> >> > handle. Why do you need the get_obj_addr() method?
> >> >
> >> > Thanks,
> >> > xiaofeng
> >> >
> >> > On 4/29/07, Tingpeng Wu <wu...@gmail.com> wrote:
> >> >> Thanks, xiaofeng,
> >> >> My test program is simple as follows:
> >> >>
> >> >> public class JNItest
> >> >>
> >> >> {
> >> >>
> >> >> static
> >> >>
> >> >> {
> >> >>
> >> >> System.loadLibrary("goodluck");
> >> >>
> >> >> }
> >> >>
> >> >>
> >> >>
> >> >> public native static int get();
> >> >>
> >> >> public native static void set(int i);
> >> >>
> >> >>
> >> >>
> >> >> public static void main(String[] args)
> >> >>
> >> >> {
> >> >>
> >> >> JNItest test = new JNItest();
> >> >>
> >> >> test.set(10);
> >> >>
> >> >> System.out.println(test.get());
> >> >>
> >> >> }
> >> >>
> >> >> }
> >> >>
> >> >> Then I use javah to produce JNItest.h and implement two method in JNItest.cpp. Then use them to build goodluck.dll. I use the latest verson of drlvm to test it, there is still an error which reports "Vm launcher meets error and needs shut up (this is translated from chinese)".
> >> >>
> >> >> The reason I asked the second problem is I want to get the address of obj in java to support the reclaimation. I plan to
> >> >> MyRuntime class, which has a native method,
> >> >> My thought now is as follows:
> >> >> 1. provide a new class named MyRuntime which has two native methods.
> >> >>     class MyRuntime
> >> >>     {
> >> >>          static
> >> >>          {
> >> >>               System.loadLibrary("runtime");
> >> >>          }
> >> >>
> >> >>         //public native static void alloc(……);
> >> >>
> >> >>          public native static void get_obj_addr(Object obj);
> >> >>
> >> >>           //public native static void free(Object obj);
> >> >>     }
> >> >>
> >> >> 2.    export the get_object_addr(jobject jobj) in vmcore to support MyRuntime.get_obj_addr(Object obj)
> >> >> 3.    export the free(unsigned size, void* address) in gc to support MyRuntime.free(Object obj)
> >> >> 4.    if above is right, I can call MyRuntime.free(obj) in java method.
> >> >>
> >> >>
> >> >>
> >> >> Is it feasible to get address that way to support the reclaimation method?
> >> >>
> >> >> Thanks,
> >> >> tingpeng
> >> >>
> >> >> ----- Original Message -----
> >> >> From: "Xiao-Feng Li" <xi...@gmail.com>
> >> >> To: <de...@harmony.apache.org>
> >> >> Sent: Sunday, April 29, 2007 11:06 AM
> >> >> Subject: Re: problem about System.loadLibrary and object's address
> >> >>
> >> >>
> >> >> > Tingpeng, can you post your program if there is no legal issue? (e.g.,
> >> >> > open a JIRA issue and attach your code there).
> >> >> >
> >> >> > For your second question, itis pretty the core part of JVM native
> >> >> > interface design. Yes, the handle is used to access Java object
> >> >> > indirectly. The idea is to support object movement during GC, then the
> >> >> > real new address of the same object can be stored to the handle. It's
> >> >> > not supposed to be used everywhere in the JVM, because that may break
> >> >> > the protocol of JNI, causing GC to fail to update the object new
> >> >> > address, e.g., if it is put into a register by your C compiler. You
> >> >> > can access it in two ways: either always use JNI interface, or
> >> >> > guarantee there is GC happening when you access it.
> >> >> >
> >> >> > Thanks,
> >> >> > xiaofeng
> >> >> >
> >> >> > On 4/29/07, 吴廷鹏 <wu...@gmail.com> wrote:
> >> >> >> Hi, all,
> >> >> >> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
> >> >> >>
> >> >> >> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
> >> >> >>
> >> >> >> jobject object_clone(JNIEnv *jenv, jobject jobj)
> >> >> >> {
> >> >> >>     ObjectHandle h = (ObjectHandle) jobj;
> >> >> >>
> >> >> >>     //aquire the target address and assign it to variable named result
> >> >> >>
> >> >> >>     memcpy(result, h->object, size);
> >> >> >>
> >> >> >> }
> >> >> >> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
> >> >> >>
> >> >> >> Thanks,
> >> >> >> tingpeng
> >> >> >>
> >> >> >
> >> >> >
> >> >> > --
> >> >> > http://xiao-feng.blogspot.com
> >> >> >
> >> >
> >> >
> >> > --
> >> > http://xiao-feng.blogspot.com
> >> >
> >
> >
> > --
> >
> > Best Regards!
> >
> > Jimmy, Jing Lv
> > China Software Development Lab, IBM
> >


-- 

Best Regards!

Jimmy, Jing Lv
China Software Development Lab, IBM

Re: problem about System.loadLibrary and object's address

[Tingpeng Wu <wu...@gmail.com>]

----- Original Message ----- 
From: "LvJimmy，Jing" <fi...@gmail.com>
To: <de...@harmony.apache.org>
Sent: Sunday, April 29, 2007 5:24 PM
Subject: Re: problem about System.loadLibrary and object's address


> 2007/4/29, Tingpeng Wu <wu...@gmail.com>:
>> Hi, xiaofeng,
>>
>> 1. I also feel very unnatural to call it through MyRuntime class, but I don't know how to call it directly. Since drlvm needs HotSpot to help it to compile the java source code, if I don't call it though an instance, the HotSpot couldn't distinguish it. If I let the Jit to add the free() call in a future time, I will not need it any more.
>>
> 
> :) Java static method can be called as SomeClass.StaticMethod, so your
> program can be written as (it is nothing related with compiler)
> public static void main(String[] args)
> {
>    set(10);
>    System.out.println(get());
> }
> 

>> 2. I added an method named "unsigned int get_object_addr(jobject jobj)" in object_handle.cpp to return the address of jobj . I can call it directly to get the object address in free() method. Since I could not assure whether it can get the right address, so I add the get_obj_addr() for test purpose. I will delete it if it can work corredtly.
>>
> 
> Ah, I don't catch well here. Why do you need a free() function here?
> If you alloc a java object (no matter in java or native), you can just
> leave it alone and let GC do everything for you. Free() is too c-style
> for Java developer :)
> In the other way, if you want to alloc some memory for other use, for
> an example, char array in c/c++, you can just keep its address(you can
> keep a jlong as void* ) and free it at last(you'd better free in this
> case or you'll get memory leak). It is such easier to keep/pass a
> jlong value than jobject handle.
> 
My thesis is to redesign the heap layout, and provide the free() method to support reclaiming the object explicitly. Then in jit module, I will add some analysis to insert some free call to reclaim the dead object in advance. The purpose is to try to improve the efficiency of program's execution. 

> 
>> 3. Another quesetion: where is runtime helper you speak of? I am afraid I need do some investigation on it.
>>
>> Thanks,
>> tingpeng
>> ----- Original Message -----
>> From: "Xiao-Feng Li" <xi...@gmail.com>
>> To: <de...@harmony.apache.org>
>> Sent: Sunday, April 29, 2007 4:05 PM
>> Subject: Re: problem about System.loadLibrary and object's address
>>
>>
>> > Tingpeng,
>> >
>> > 1. Your native is static native, why do you call it through an instance?
>> > 2. You probably need to use runtime helper for the object direct free
>> > in Java app, because the default JNI call path will save the object
>> > handle (and passes the reference address as a root entry during GC
>> > enumeration). For your purpose, there is no GC happening in free(),
>> > so it probably works with a stale object reference (freed) in the
>> > object handle.
>> > 3. You can use free() directly to retrieve its object address from the
>> > handle. Why do you need the get_obj_addr() method?
>> >
>> > Thanks,
>> > xiaofeng
>> >
>> > On 4/29/07, Tingpeng Wu <wu...@gmail.com> wrote:
>> >> Thanks, xiaofeng,
>> >> My test program is simple as follows:
>> >>
>> >> public class JNItest
>> >>
>> >> {
>> >>
>> >> static
>> >>
>> >> {
>> >>
>> >> System.loadLibrary("goodluck");
>> >>
>> >> }
>> >>
>> >>
>> >>
>> >> public native static int get();
>> >>
>> >> public native static void set(int i);
>> >>
>> >>
>> >>
>> >> public static void main(String[] args)
>> >>
>> >> {
>> >>
>> >> JNItest test = new JNItest();
>> >>
>> >> test.set(10);
>> >>
>> >> System.out.println(test.get());
>> >>
>> >> }
>> >>
>> >> }
>> >>
>> >> Then I use javah to produce JNItest.h and implement two method in JNItest.cpp. Then use them to build goodluck.dll. I use the latest verson of drlvm to test it, there is still an error which reports "Vm launcher meets error and needs shut up (this is translated from chinese)".
>> >>
>> >> The reason I asked the second problem is I want to get the address of obj in java to support the reclaimation. I plan to
>> >> MyRuntime class, which has a native method,
>> >> My thought now is as follows:
>> >> 1. provide a new class named MyRuntime which has two native methods.
>> >>     class MyRuntime
>> >>     {
>> >>          static
>> >>          {
>> >>               System.loadLibrary("runtime");
>> >>          }
>> >>
>> >>         //public native static void alloc(……);
>> >>
>> >>          public native static void get_obj_addr(Object obj);
>> >>
>> >>           //public native static void free(Object obj);
>> >>     }
>> >>
>> >> 2.    export the get_object_addr(jobject jobj) in vmcore to support MyRuntime.get_obj_addr(Object obj)
>> >> 3.    export the free(unsigned size, void* address) in gc to support MyRuntime.free(Object obj)
>> >> 4.    if above is right, I can call MyRuntime.free(obj) in java method.
>> >>
>> >>
>> >>
>> >> Is it feasible to get address that way to support the reclaimation method?
>> >>
>> >> Thanks,
>> >> tingpeng
>> >>
>> >> ----- Original Message -----
>> >> From: "Xiao-Feng Li" <xi...@gmail.com>
>> >> To: <de...@harmony.apache.org>
>> >> Sent: Sunday, April 29, 2007 11:06 AM
>> >> Subject: Re: problem about System.loadLibrary and object's address
>> >>
>> >>
>> >> > Tingpeng, can you post your program if there is no legal issue? (e.g.,
>> >> > open a JIRA issue and attach your code there).
>> >> >
>> >> > For your second question, itis pretty the core part of JVM native
>> >> > interface design. Yes, the handle is used to access Java object
>> >> > indirectly. The idea is to support object movement during GC, then the
>> >> > real new address of the same object can be stored to the handle. It's
>> >> > not supposed to be used everywhere in the JVM, because that may break
>> >> > the protocol of JNI, causing GC to fail to update the object new
>> >> > address, e.g., if it is put into a register by your C compiler. You
>> >> > can access it in two ways: either always use JNI interface, or
>> >> > guarantee there is GC happening when you access it.
>> >> >
>> >> > Thanks,
>> >> > xiaofeng
>> >> >
>> >> > On 4/29/07, 吴廷鹏 <wu...@gmail.com> wrote:
>> >> >> Hi, all,
>> >> >> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
>> >> >>
>> >> >> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
>> >> >>
>> >> >> jobject object_clone(JNIEnv *jenv, jobject jobj)
>> >> >> {
>> >> >>     ObjectHandle h = (ObjectHandle) jobj;
>> >> >>
>> >> >>     //aquire the target address and assign it to variable named result
>> >> >>
>> >> >>     memcpy(result, h->object, size);
>> >> >>
>> >> >> }
>> >> >> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
>> >> >>
>> >> >> Thanks,
>> >> >> tingpeng
>> >> >>
>> >> >
>> >> >
>> >> > --
>> >> > http://xiao-feng.blogspot.com
>> >> >
>> >
>> >
>> > --
>> > http://xiao-feng.blogspot.com
>> >
> 
> 
> -- 
> 
> Best Regards!
> 
> Jimmy, Jing Lv
> China Software Development Lab, IBM
>

Re: problem about System.loadLibrary and object's address

[LvJimmy，Jing <fi...@gmail.com>]

2007/4/29, Tingpeng Wu <wu...@gmail.com>:
> Hi, xiaofeng,
>
> 1. I also feel very unnatural to call it through MyRuntime class, but I don't know how to call it directly. Since drlvm needs HotSpot to help it to compile the java source code, if I don't call it though an instance, the HotSpot couldn't distinguish it. If I let the Jit to add the free() call in a future time, I will not need it any more.
>

:) Java static method can be called as SomeClass.StaticMethod, so your
program can be written as (it is nothing related with compiler)
public static void main(String[] args)
{
    set(10);
    System.out.println(get());
}

> 2. I added an method named "unsigned int get_object_addr(jobject jobj)" in object_handle.cpp to return the address of jobj . I can call it directly to get the object address in free() method. Since I could not assure whether it can get the right address, so I add the get_obj_addr() for test purpose. I will delete it if it can work corredtly.
>

Ah, I don't catch well here. Why do you need a free() function here?
If you alloc a java object (no matter in java or native), you can just
leave it alone and let GC do everything for you. Free() is too c-style
for Java developer :)
In the other way, if you want to alloc some memory for other use, for
an example, char array in c/c++, you can just keep its address(you can
keep a jlong as void* ) and free it at last(you'd better free in this
case or you'll get memory leak). It is such easier to keep/pass a
jlong value than jobject handle.


> 3. Another quesetion: where is runtime helper you speak of? I am afraid I need do some investigation on it.
>
> Thanks,
> tingpeng
> ----- Original Message -----
> From: "Xiao-Feng Li" <xi...@gmail.com>
> To: <de...@harmony.apache.org>
> Sent: Sunday, April 29, 2007 4:05 PM
> Subject: Re: problem about System.loadLibrary and object's address
>
>
> > Tingpeng,
> >
> > 1. Your native is static native, why do you call it through an instance?
> > 2. You probably need to use runtime helper for the object direct free
> > in Java app, because the default JNI call path will save the object
> > handle (and passes the reference address as a root entry during GC
> > enumeration). For your purpose, there is no GC happening in free(),
> > so it probably works with a stale object reference (freed) in the
> > object handle.
> > 3. You can use free() directly to retrieve its object address from the
> > handle. Why do you need the get_obj_addr() method?
> >
> > Thanks,
> > xiaofeng
> >
> > On 4/29/07, Tingpeng Wu <wu...@gmail.com> wrote:
> >> Thanks, xiaofeng,
> >> My test program is simple as follows:
> >>
> >> public class JNItest
> >>
> >> {
> >>
> >> static
> >>
> >> {
> >>
> >> System.loadLibrary("goodluck");
> >>
> >> }
> >>
> >>
> >>
> >> public native static int get();
> >>
> >> public native static void set(int i);
> >>
> >>
> >>
> >> public static void main(String[] args)
> >>
> >> {
> >>
> >> JNItest test = new JNItest();
> >>
> >> test.set(10);
> >>
> >> System.out.println(test.get());
> >>
> >> }
> >>
> >> }
> >>
> >> Then I use javah to produce JNItest.h and implement two method in JNItest.cpp. Then use them to build goodluck.dll. I use the latest verson of drlvm to test it, there is still an error which reports "Vm launcher meets error and needs shut up (this is translated from chinese)".
> >>
> >> The reason I asked the second problem is I want to get the address of obj in java to support the reclaimation. I plan to
> >> MyRuntime class, which has a native method,
> >> My thought now is as follows:
> >> 1. provide a new class named MyRuntime which has two native methods.
> >>     class MyRuntime
> >>     {
> >>          static
> >>          {
> >>               System.loadLibrary("runtime");
> >>          }
> >>
> >>         //public native static void alloc(……);
> >>
> >>          public native static void get_obj_addr(Object obj);
> >>
> >>           //public native static void free(Object obj);
> >>     }
> >>
> >> 2.    export the get_object_addr(jobject jobj) in vmcore to support MyRuntime.get_obj_addr(Object obj)
> >> 3.    export the free(unsigned size, void* address) in gc to support MyRuntime.free(Object obj)
> >> 4.    if above is right, I can call MyRuntime.free(obj) in java method.
> >>
> >>
> >>
> >> Is it feasible to get address that way to support the reclaimation method?
> >>
> >> Thanks,
> >> tingpeng
> >>
> >> ----- Original Message -----
> >> From: "Xiao-Feng Li" <xi...@gmail.com>
> >> To: <de...@harmony.apache.org>
> >> Sent: Sunday, April 29, 2007 11:06 AM
> >> Subject: Re: problem about System.loadLibrary and object's address
> >>
> >>
> >> > Tingpeng, can you post your program if there is no legal issue? (e.g.,
> >> > open a JIRA issue and attach your code there).
> >> >
> >> > For your second question, itis pretty the core part of JVM native
> >> > interface design. Yes, the handle is used to access Java object
> >> > indirectly. The idea is to support object movement during GC, then the
> >> > real new address of the same object can be stored to the handle. It's
> >> > not supposed to be used everywhere in the JVM, because that may break
> >> > the protocol of JNI, causing GC to fail to update the object new
> >> > address, e.g., if it is put into a register by your C compiler. You
> >> > can access it in two ways: either always use JNI interface, or
> >> > guarantee there is GC happening when you access it.
> >> >
> >> > Thanks,
> >> > xiaofeng
> >> >
> >> > On 4/29/07, 吴廷鹏 <wu...@gmail.com> wrote:
> >> >> Hi, all,
> >> >> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
> >> >>
> >> >> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
> >> >>
> >> >> jobject object_clone(JNIEnv *jenv, jobject jobj)
> >> >> {
> >> >>     ObjectHandle h = (ObjectHandle) jobj;
> >> >>
> >> >>     //aquire the target address and assign it to variable named result
> >> >>
> >> >>     memcpy(result, h->object, size);
> >> >>
> >> >> }
> >> >> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
> >> >>
> >> >> Thanks,
> >> >> tingpeng
> >> >>
> >> >
> >> >
> >> > --
> >> > http://xiao-feng.blogspot.com
> >> >
> >
> >
> > --
> > http://xiao-feng.blogspot.com
> >


-- 

Best Regards!

Jimmy, Jing Lv
China Software Development Lab, IBM

Re: problem about System.loadLibrary and object's address

[Tingpeng Wu <wu...@gmail.com>]

Hi, xiaofeng,

1. I also feel very unnatural to call it through MyRuntime class, but I don't know how to call it directly. Since drlvm needs HotSpot to help it to compile the java source code, if I don't call it though an instance, the HotSpot couldn't distinguish it. If I let the Jit to add the free() call in a future time, I will not need it any more.

2. I added an method named "unsigned int get_object_addr(jobject jobj)" in object_handle.cpp to return the address of jobj . I can call it directly to get the object address in free() method. Since I could not assure whether it can get the right address, so I add the get_obj_addr() for test purpose. I will delete it if it can work corredtly. 

3. Another quesetion: where is runtime helper you speak of? I am afraid I need do some investigation on it.

Thanks,
tingpeng 
----- Original Message ----- 
From: "Xiao-Feng Li" <xi...@gmail.com>
To: <de...@harmony.apache.org>
Sent: Sunday, April 29, 2007 4:05 PM
Subject: Re: problem about System.loadLibrary and object's address


> Tingpeng,
> 
> 1. Your native is static native, why do you call it through an instance?
> 2. You probably need to use runtime helper for the object direct free
> in Java app, because the default JNI call path will save the object
> handle (and passes the reference address as a root entry during GC
> enumeration). For your purpose, there is no GC happening in free(),
> so it probably works with a stale object reference (freed) in the
> object handle.
> 3. You can use free() directly to retrieve its object address from the
> handle. Why do you need the get_obj_addr() method?
> 
> Thanks,
> xiaofeng
> 
> On 4/29/07, Tingpeng Wu <wu...@gmail.com> wrote:
>> Thanks, xiaofeng,
>> My test program is simple as follows:
>>
>> public class JNItest
>>
>> {
>>
>> static
>>
>> {
>>
>> System.loadLibrary("goodluck");
>>
>> }
>>
>>
>>
>> public native static int get();
>>
>> public native static void set(int i);
>>
>>
>>
>> public static void main(String[] args)
>>
>> {
>>
>> JNItest test = new JNItest();
>>
>> test.set(10);
>>
>> System.out.println(test.get());
>>
>> }
>>
>> }
>>
>> Then I use javah to produce JNItest.h and implement two method in JNItest.cpp. Then use them to build goodluck.dll. I use the latest verson of drlvm to test it, there is still an error which reports "Vm launcher meets error and needs shut up (this is translated from chinese)".
>>
>> The reason I asked the second problem is I want to get the address of obj in java to support the reclaimation. I plan to
>> MyRuntime class, which has a native method,
>> My thought now is as follows:
>> 1. provide a new class named MyRuntime which has two native methods.
>>     class MyRuntime
>>     {
>>          static
>>          {
>>               System.loadLibrary("runtime");
>>          }
>>
>>         //public native static void alloc(……);
>>
>>          public native static void get_obj_addr(Object obj);
>>
>>           //public native static void free(Object obj);
>>     }
>>
>> 2.    export the get_object_addr(jobject jobj) in vmcore to support MyRuntime.get_obj_addr(Object obj)
>> 3.    export the free(unsigned size, void* address) in gc to support MyRuntime.free(Object obj)
>> 4.    if above is right, I can call MyRuntime.free(obj) in java method.
>>
>>
>>
>> Is it feasible to get address that way to support the reclaimation method?
>>
>> Thanks,
>> tingpeng
>>
>> ----- Original Message -----
>> From: "Xiao-Feng Li" <xi...@gmail.com>
>> To: <de...@harmony.apache.org>
>> Sent: Sunday, April 29, 2007 11:06 AM
>> Subject: Re: problem about System.loadLibrary and object's address
>>
>>
>> > Tingpeng, can you post your program if there is no legal issue? (e.g.,
>> > open a JIRA issue and attach your code there).
>> >
>> > For your second question, itis pretty the core part of JVM native
>> > interface design. Yes, the handle is used to access Java object
>> > indirectly. The idea is to support object movement during GC, then the
>> > real new address of the same object can be stored to the handle. It's
>> > not supposed to be used everywhere in the JVM, because that may break
>> > the protocol of JNI, causing GC to fail to update the object new
>> > address, e.g., if it is put into a register by your C compiler. You
>> > can access it in two ways: either always use JNI interface, or
>> > guarantee there is GC happening when you access it.
>> >
>> > Thanks,
>> > xiaofeng
>> >
>> > On 4/29/07, 吴廷鹏 <wu...@gmail.com> wrote:
>> >> Hi, all,
>> >> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
>> >>
>> >> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
>> >>
>> >> jobject object_clone(JNIEnv *jenv, jobject jobj)
>> >> {
>> >>     ObjectHandle h = (ObjectHandle) jobj;
>> >>
>> >>     //aquire the target address and assign it to variable named result
>> >>
>> >>     memcpy(result, h->object, size);
>> >>
>> >> }
>> >> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
>> >>
>> >> Thanks,
>> >> tingpeng
>> >>
>> >
>> >
>> > --
>> > http://xiao-feng.blogspot.com
>> >
> 
> 
> -- 
> http://xiao-feng.blogspot.com
>

Re: problem about System.loadLibrary and object's address

[Xiao-Feng Li <xi...@gmail.com>]

Tingpeng,

1. Your native is static native, why do you call it through an instance?
2. You probably need to use runtime helper for the object direct free
in Java app, because the default JNI call path will save the object
handle (and passes the reference address as a root entry during GC
enumeration). For your purpose, there is no GC happening in free(),
so it probably works with a stale object reference (freed) in the
object handle.
3. You can use free() directly to retrieve its object address from the
handle. Why do you need the get_obj_addr() method?

Thanks,
xiaofeng

On 4/29/07, Tingpeng Wu <wu...@gmail.com> wrote:
> Thanks, xiaofeng,
> My test program is simple as follows:
>
> public class JNItest
>
> {
>
> static
>
> {
>
> System.loadLibrary("goodluck");
>
> }
>
>
>
> public native static int get();
>
> public native static void set(int i);
>
>
>
> public static void main(String[] args)
>
> {
>
> JNItest test = new JNItest();
>
> test.set(10);
>
> System.out.println(test.get());
>
> }
>
> }
>
> Then I use javah to produce JNItest.h and implement two method in JNItest.cpp. Then use them to build goodluck.dll. I use the latest verson of drlvm to test it, there is still an error which reports "Vm launcher meets error and needs shut up (this is translated from chinese)".
>
> The reason I asked the second problem is I want to get the address of obj in java to support the reclaimation. I plan to
> MyRuntime class, which has a native method,
> My thought now is as follows:
> 1. provide a new class named MyRuntime which has two native methods.
>     class MyRuntime
>     {
>          static
>          {
>               System.loadLibrary("runtime");
>          }
>
>         //public native static void alloc(……);
>
>          public native static void get_obj_addr(Object obj);
>
>           //public native static void free(Object obj);
>     }
>
> 2.    export the get_object_addr(jobject jobj) in vmcore to support MyRuntime.get_obj_addr(Object obj)
> 3.    export the free(unsigned size, void* address) in gc to support MyRuntime.free(Object obj)
> 4.    if above is right, I can call MyRuntime.free(obj) in java method.
>
>
>
> Is it feasible to get address that way to support the reclaimation method?
>
> Thanks,
> tingpeng
>
> ----- Original Message -----
> From: "Xiao-Feng Li" <xi...@gmail.com>
> To: <de...@harmony.apache.org>
> Sent: Sunday, April 29, 2007 11:06 AM
> Subject: Re: problem about System.loadLibrary and object's address
>
>
> > Tingpeng, can you post your program if there is no legal issue? (e.g.,
> > open a JIRA issue and attach your code there).
> >
> > For your second question, itis pretty the core part of JVM native
> > interface design. Yes, the handle is used to access Java object
> > indirectly. The idea is to support object movement during GC, then the
> > real new address of the same object can be stored to the handle. It's
> > not supposed to be used everywhere in the JVM, because that may break
> > the protocol of JNI, causing GC to fail to update the object new
> > address, e.g., if it is put into a register by your C compiler. You
> > can access it in two ways: either always use JNI interface, or
> > guarantee there is GC happening when you access it.
> >
> > Thanks,
> > xiaofeng
> >
> > On 4/29/07, 吴廷鹏 <wu...@gmail.com> wrote:
> >> Hi, all,
> >> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
> >>
> >> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
> >>
> >> jobject object_clone(JNIEnv *jenv, jobject jobj)
> >> {
> >>     ObjectHandle h = (ObjectHandle) jobj;
> >>
> >>     //aquire the target address and assign it to variable named result
> >>
> >>     memcpy(result, h->object, size);
> >>
> >> }
> >> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
> >>
> >> Thanks,
> >> tingpeng
> >>
> >
> >
> > --
> > http://xiao-feng.blogspot.com
> >


-- 
http://xiao-feng.blogspot.com

Re: problem about System.loadLibrary and object's address

[Tingpeng Wu <wu...@gmail.com>]

Thanks, xiaofeng,
My test program is simple as follows: 

public class JNItest 

{ 

static 

{ 

System.loadLibrary("goodluck"); 

} 



public native static int get(); 

public native static void set(int i); 



public static void main(String[] args) 

{ 

JNItest test = new JNItest(); 

test.set(10); 

System.out.println(test.get()); 

} 

} 

Then I use javah to produce JNItest.h and implement two method in JNItest.cpp. Then use them to build goodluck.dll. I use the latest verson of drlvm to test it, there is still an error which reports "Vm launcher meets error and needs shut up (this is translated from chinese)".

The reason I asked the second problem is I want to get the address of obj in java to support the reclaimation. I plan to 
MyRuntime class, which has a native method,
My thought now is as follows:
1. provide a new class named MyRuntime which has two native methods.
    class MyRuntime
    {
         static
         {
              System.loadLibrary("runtime");
         }

        //public native static void alloc(……);

         public native static void get_obj_addr(Object obj); 

          //public native static void free(Object obj);
    }

2.    export the get_object_addr(jobject jobj) in vmcore to support MyRuntime.get_obj_addr(Object obj)
3.    export the free(unsigned size, void* address) in gc to support MyRuntime.free(Object obj)
4.    if above is right, I can call MyRuntime.free(obj) in java method.



Is it feasible to get address that way to support the reclaimation method? 

Thanks,
tingpeng

----- Original Message ----- 
From: "Xiao-Feng Li" <xi...@gmail.com>
To: <de...@harmony.apache.org>
Sent: Sunday, April 29, 2007 11:06 AM
Subject: Re: problem about System.loadLibrary and object's address


> Tingpeng, can you post your program if there is no legal issue? (e.g.,
> open a JIRA issue and attach your code there).
> 
> For your second question, itis pretty the core part of JVM native
> interface design. Yes, the handle is used to access Java object
> indirectly. The idea is to support object movement during GC, then the
> real new address of the same object can be stored to the handle. It's
> not supposed to be used everywhere in the JVM, because that may break
> the protocol of JNI, causing GC to fail to update the object new
> address, e.g., if it is put into a register by your C compiler. You
> can access it in two ways: either always use JNI interface, or
> guarantee there is GC happening when you access it.
> 
> Thanks,
> xiaofeng
> 
> On 4/29/07, 吴廷鹏 <wu...@gmail.com> wrote:
>> Hi, all,
>> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
>>
>> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
>>
>> jobject object_clone(JNIEnv *jenv, jobject jobj)
>> {
>>     ObjectHandle h = (ObjectHandle) jobj;
>>
>>     //aquire the target address and assign it to variable named result
>>
>>     memcpy(result, h->object, size);
>>
>> }
>> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
>>
>> Thanks,
>> tingpeng
>>
> 
> 
> -- 
> http://xiao-feng.blogspot.com
>

Re: problem about System.loadLibrary and object's address

[Xiao-Feng Li <xi...@gmail.com>]

Tingpeng, can you post your program if there is no legal issue? (e.g.,
open a JIRA issue and attach your code there).

For your second question, itis pretty the core part of JVM native
interface design. Yes, the handle is used to access Java object
indirectly. The idea is to support object movement during GC, then the
real new address of the same object can be stored to the handle. It's
not supposed to be used everywhere in the JVM, because that may break
the protocol of JNI, causing GC to fail to update the object new
address, e.g., if it is put into a register by your C compiler. You
can access it in two ways: either always use JNI interface, or
guarantee there is GC happening when you access it.

Thanks,
xiaofeng

On 4/29/07, 吴廷鹏 <wu...@gmail.com> wrote:
> Hi, all,
> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
>
> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
>
> jobject object_clone(JNIEnv *jenv, jobject jobj)
> {
>     ObjectHandle h = (ObjectHandle) jobj;
>
>     //aquire the target address and assign it to variable named result
>
>     memcpy(result, h->object, size);
>
> }
> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
>
> Thanks,
> tingpeng
>


-- 
http://xiao-feng.blogspot.com

Re: problem about System.loadLibrary and object's address

[Tingpeng Wu <wu...@gmail.com>]

LvJimmy, thanks for your warnning. Since I just plan to develop some reseach on DRLVM platform. I will not run my benchmark on other JVM.

----- Original Message ----- 
From: "LvJimmy，Jing" <fi...@gmail.com>
To: <de...@harmony.apache.org>
Sent: Sunday, April 29, 2007 5:04 PM
Subject: Re: problem about System.loadLibrary and object's address


> 2007/4/29, 吴廷鹏 <wu...@gmail.com>:
>> Hi, all,
>> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
>>
>> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
>>
>> jobject object_clone(JNIEnv *jenv, jobject jobj)
>> {
>>     ObjectHandle h = (ObjectHandle) jobj;
>>
>>     //aquire the target address and assign it to variable named result
>>
>>     memcpy(result, h->object, size);
>>
>> }
>> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
>>
> 
> I suggest you ALWAYS use API structure and methods when writing native
> codes(JNI, JVMTI, etc). The code you list here is too tricky and
> depends on real implementation of JVM, I believe other JVM supports
> Harmony may not use such structure, so your program may fail with
> them, this is not you want, right?
> I'm not sure what you want to do, why you need to access the address
> of the object?
> 
>> Thanks,
>> tingpeng
>>
> 
> 
> -- 
> 
> Best Regards!
> 
> Jimmy, Jing Lv
> China Software Development Lab, IBM
>

Re: problem about System.loadLibrary and object's address

[LvJimmy，Jing <fi...@gmail.com>]

2007/4/29, 吴廷鹏 <wu...@gmail.com>:
> Hi, all,
> when I use drlvm to execute my program, I found that when program has System.loadLibrary call, there is always an error which reports "java.lang.outofmemoryerror <no stack trace available>". The same program can run on Hotspot. Why this happens and how to solve it?
>
> Another question, I read the implementation code of Object.clone method in Object_generic.cpp.
>
> jobject object_clone(JNIEnv *jenv, jobject jobj)
> {
>     ObjectHandle h = (ObjectHandle) jobj;
>
>     //aquire the target address and assign it to variable named result
>
>     memcpy(result, h->object, size);
>
> }
> According to my comprehension, h->object is the address of java object. Is it ture? Does this means I can use the same way to get the address of object in vmcore's other place provided the necessary head file is included?
>

I suggest you ALWAYS use API structure and methods when writing native
codes(JNI, JVMTI, etc). The code you list here is too tricky and
depends on real implementation of JVM, I believe other JVM supports
Harmony may not use such structure, so your program may fail with
them, this is not you want, right?
I'm not sure what you want to do, why you need to access the address
of the object?

> Thanks,
> tingpeng
>


-- 

Best Regards!

Jimmy, Jing Lv
China Software Development Lab, IBM