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Posted to kato-spec@incubator.apache.org by Stuart Monteith <st...@stoo.me.uk> on 2009/04/24 13:31:42 UTC
Conference call
Hello all,
I have posted the presentation that we will be going through on the
Kato Wiki.
You can link to it here:
http://cwiki.apache.org/confluence/display/KATO/API+Walkthrough
The recording will be made available in the same place, at the very
least the transcription and notes will be there.
If you are unable to join the meeting on Sametime Unyte here:
https://www.webdialogs.com/join/ you will should be able to go through
the presentation from the wiki.
Speak to you at 1500.
Stuart
Re: Conference call
Posted by Steve Poole <sp...@googlemail.com>.
On Fri, Apr 24, 2009 at 4:01 PM, Robert Burrell Donkin <
robertburrelldonkin@gmail.com> wrote:
> On Fri, Apr 24, 2009 at 2:31 PM, Stuart Monteith <st...@stoo.me.uk>
> wrote:
> > Hello all,
> > I have posted the presentation that we will be going through on the
> Kato
> > Wiki.
> > You can link to it here:
> > http://cwiki.apache.org/confluence/display/KATO/API+Walkthrough
> > The recording will be made available in the same place, at the very least
> > the transcription and notes will be there.
> >
> > If you are unable to join the meeting on Sametime Unyte here:
> > https://www.webdialogs.com/join/ you will should be able to go through
> the
> > presentation from the wiki.
> >
> > Speak to you at 1500.
>
> timezone?
UTC apparently. 16:00 UK time.
>
>
> - robert
>
Re: Conference call
Posted by Robert Burrell Donkin <ro...@gmail.com>.
On Fri, Apr 24, 2009 at 2:31 PM, Stuart Monteith <st...@stoo.me.uk> wrote:
> Hello all,
> I have posted the presentation that we will be going through on the Kato
> Wiki.
> You can link to it here:
> http://cwiki.apache.org/confluence/display/KATO/API+Walkthrough
> The recording will be made available in the same place, at the very least
> the transcription and notes will be there.
>
> If you are unable to join the meeting on Sametime Unyte here:
> https://www.webdialogs.com/join/ you will should be able to go through the
> presentation from the wiki.
>
> Speak to you at 1500.
timezone?
- robert
RE: Conference call
Posted by "Bobrovsky, Konstantin S" <ko...@intel.com>.
Hello Stuart,
> Is it true to say that a reference, implementation wise, could always be
> reported as a pointer?
Just in case: I assume a "reference" is always an address of a location in memory where an entity uniquely identifying a Java object (usually its address on heap) resides. With this assumption - yes (to the best of my knowledge).
Important side note (does not directly relate to the derived pointer discussion): object addresses stored in fields, arrays of reference types, etc. may be "compressed" in real 64-bit VMs (I know this is true for Hotspot, JRockit). That means that to get real object's address on heap from its compressed representation one has to "decode" it. (In Hotspot this is real_addr = heap_base + compressed_addr * 8). Not sure if this can affect the API. Probably not, as JavaReference can abstract away "compressed-ness" of the target object. But I just wanted to bring this up in case you would guess other places in the API where changes could be desired.
> Would that satisfy your requirement for direct pointer?
I think yes, pretty much. Just few notes:
(1) Can getReferenceType() return something like REFERENCE_DERIVED (or REFERENCE_DIRECT in your terms) so that it is easily distinguishable via an integer comparison rather than via String.equals()?
(2) If an array element is of a reference type, how do we get the Java object the element contains? getTarget()'s semantics is already occupied to return the base. Maybe the base could be returned through getSource(), and getTarget() would obey current contract to return referenced object (or additionally throw an exception if the element type is not a reference Java type)?
(3) [Small terminology question] I never heard "direct pointer" term to be used to describe a derived pointer. The only terms I heard were "derived" or "interior" (meaning the pointer points to an interior part of some Java object). But if you think "direct" is better - that's OK.
> Would it make sense in other situations too?
Do you mean in situations involving derived pointers other than "array element pointer - array base"? Yes, it would. The other situations which I can think of are "instance field pointer - enclosing Java object", " static field pointer - enclosing Java class object", "class or vtable pointer in a Java object header - the class or vtable object"
Thanks,
Konst
-----Original Message-----
From: Stuart Monteith [mailto:stukato@stoo.me.uk]
Sent: Wednesday, April 29, 2009 7:40 PM
To: kato-spec@incubator.apache.org
Subject: Re: Conference call
Hello Konstantin,
I understand what you mean. The API could report that there was a
reference to the array, but nothing about where it the array it was
referencing, like so:
JavaReference:
getDescription() - "Direct reference".
getReferenceType() - REFERENCE_UNKNOWN
getRootType() - HEAP_ROOT_THREAD
getSource() - null
getTarget() - reference to the JavaObject representing the array
The API doesn't report anything more specific than the existence of the
reference, its type and its destination.. The description string could
have anything put into it, but I would expect the string contents to be
constant.
Is it true to say that a reference, implementation wise, could always be
reported as a pointer?
Expanding the above scenario:
JavaReference:
getDescription() - "Direct reference".
getReferenceType() - REFERENCE_UNKNOWN
getRootType() - HEAP_ROOT_THREAD
getSource() - null
getTarget() - reference to the JavaObject representing the array
getPointer() - actual reference value.
Such that normally ((JavaObject)JavaReference.getTarget()).getID() would
be the base pointer and this would be equal to
JavaReference.getPointer(). But for direct references getTarget() would
report the JavaObject for the array, which would be the base, but
getPointer() would return a pointer within that JavaObject array.
Would that satisfy your requirement for direct pointer? Would it make
sense in other situations too?
Regards,
Stuart
Bobrovsky, Konstantin S wrote:
>> - I will provide more explanations about my comment on derived pointer
>> support early next week.
>>
>
> First, let me describe what I mean by "derived pointer" (might be well-known term to those who worked with the Hotspot JVM)
> This is a pointer which is logically bound to some "base" java object. For example, pointer to a memory location holding an array element (regardless of the element type) is a derived pointer, and the array object itself is the base object. Derived pointers are "produced" by JIT-ed code (e.g. to quickly access array elements, current element's address might be kept in a register), and during GC their value must be updated whenever the GC moves the base object (basically, derived pointer value should change by the same number the address of the base object changes). To support that, derived pointer is reported to GC as "live" always together with its base (whose live range is sometimes artificially stretched to match one of the derived pointer). At least two VMs I worked with employ this concept: Hotspot and Harmony.
>
> My comment was whether it is possible to find/identify live derived pointers + bases through a JavaStackFrame instance. It might be interesting for an engineer analyzing a post-mortem dump to learn where the derived pointers and their bases are for the same reasons as it might be interesting for him to find "usual" heap roots.
>
>
> Hope this helps,
> Konst
>
> Intel Novosibirsk
> Closed Joint Stock Company Intel A/O
> Registered legal address: Krylatsky Hills Business Park,
> 17 Krylatskaya Str., Bldg 4, Moscow 121614,
> Russian Federation
>
>
> -----Original Message-----
> From: Bobrovsky, Konstantin S
> Sent: Friday, April 24, 2009 11:13 PM
> To: 'kato-spec@incubator.apache.org'; kato-dev@incubator.apache.org
> Subject: RE: Conference call
>
> Hello all,
>
> Quick follow up to the meeting:
> - JavaMethod
> In many VMs each method may have multiple compiled versions (even co-existing at the same time). I think the API should provide access to all of them. Will client be able to access all of them via getCompiledSections()?
>
> - ImageStackFrame
> It would be good if the API would support architectures with additional register stack (such as Itanium). E.g. through an additional pointer to the base of the register stack frame.
>
> - I will provide more explanations about my comment on derived pointer support early next week.
>
> Thanks,
> Konst
>
> Intel Novosibirsk
> Closed Joint Stock Company Intel A/O
> Registered legal address: Krylatsky Hills Business Park,
> 17 Krylatskaya Str., Bldg 4, Moscow 121614,
> Russian Federation
>
>
> -----Original Message-----
> From: Stuart Monteith [mailto:stukato@stoo.me.uk]
> Sent: Friday, April 24, 2009 8:32 PM
> To: kato-dev@incubator.apache.org; kato-spec@incubator.apache.org
> Subject: Conference call
>
> Hello all,
> I have posted the presentation that we will be going through on the
> Kato Wiki.
> You can link to it here:
> http://cwiki.apache.org/confluence/display/KATO/API+Walkthrough
> The recording will be made available in the same place, at the very
> least the transcription and notes will be there.
>
> If you are unable to join the meeting on Sametime Unyte here:
> https://www.webdialogs.com/join/ you will should be able to go through
> the presentation from the wiki.
>
> Speak to you at 1500.
>
> Stuart
>
>
>
Re: Conference call
Posted by Stuart Monteith <st...@stoo.me.uk>.
Hello Konstantin,
I understand what you mean. The API could report that there was a
reference to the array, but nothing about where it the array it was
referencing, like so:
JavaReference:
getDescription() - "Direct reference".
getReferenceType() - REFERENCE_UNKNOWN
getRootType() - HEAP_ROOT_THREAD
getSource() - null
getTarget() - reference to the JavaObject representing the array
The API doesn't report anything more specific than the existence of the
reference, its type and its destination.. The description string could
have anything put into it, but I would expect the string contents to be
constant.
Is it true to say that a reference, implementation wise, could always be
reported as a pointer?
Expanding the above scenario:
JavaReference:
getDescription() - "Direct reference".
getReferenceType() - REFERENCE_UNKNOWN
getRootType() - HEAP_ROOT_THREAD
getSource() - null
getTarget() - reference to the JavaObject representing the array
getPointer() - actual reference value.
Such that normally ((JavaObject)JavaReference.getTarget()).getID() would
be the base pointer and this would be equal to
JavaReference.getPointer(). But for direct references getTarget() would
report the JavaObject for the array, which would be the base, but
getPointer() would return a pointer within that JavaObject array.
Would that satisfy your requirement for direct pointer? Would it make
sense in other situations too?
Regards,
Stuart
Bobrovsky, Konstantin S wrote:
>> - I will provide more explanations about my comment on derived pointer
>> support early next week.
>>
>
> First, let me describe what I mean by "derived pointer" (might be well-known term to those who worked with the Hotspot JVM)
> This is a pointer which is logically bound to some "base" java object. For example, pointer to a memory location holding an array element (regardless of the element type) is a derived pointer, and the array object itself is the base object. Derived pointers are "produced" by JIT-ed code (e.g. to quickly access array elements, current element's address might be kept in a register), and during GC their value must be updated whenever the GC moves the base object (basically, derived pointer value should change by the same number the address of the base object changes). To support that, derived pointer is reported to GC as "live" always together with its base (whose live range is sometimes artificially stretched to match one of the derived pointer). At least two VMs I worked with employ this concept: Hotspot and Harmony.
>
> My comment was whether it is possible to find/identify live derived pointers + bases through a JavaStackFrame instance. It might be interesting for an engineer analyzing a post-mortem dump to learn where the derived pointers and their bases are for the same reasons as it might be interesting for him to find "usual" heap roots.
>
>
> Hope this helps,
> Konst
>
> Intel Novosibirsk
> Closed Joint Stock Company Intel A/O
> Registered legal address: Krylatsky Hills Business Park,
> 17 Krylatskaya Str., Bldg 4, Moscow 121614,
> Russian Federation
>
>
> -----Original Message-----
> From: Bobrovsky, Konstantin S
> Sent: Friday, April 24, 2009 11:13 PM
> To: 'kato-spec@incubator.apache.org'; kato-dev@incubator.apache.org
> Subject: RE: Conference call
>
> Hello all,
>
> Quick follow up to the meeting:
> - JavaMethod
> In many VMs each method may have multiple compiled versions (even co-existing at the same time). I think the API should provide access to all of them. Will client be able to access all of them via getCompiledSections()?
>
> - ImageStackFrame
> It would be good if the API would support architectures with additional register stack (such as Itanium). E.g. through an additional pointer to the base of the register stack frame.
>
> - I will provide more explanations about my comment on derived pointer support early next week.
>
> Thanks,
> Konst
>
> Intel Novosibirsk
> Closed Joint Stock Company Intel A/O
> Registered legal address: Krylatsky Hills Business Park,
> 17 Krylatskaya Str., Bldg 4, Moscow 121614,
> Russian Federation
>
>
> -----Original Message-----
> From: Stuart Monteith [mailto:stukato@stoo.me.uk]
> Sent: Friday, April 24, 2009 8:32 PM
> To: kato-dev@incubator.apache.org; kato-spec@incubator.apache.org
> Subject: Conference call
>
> Hello all,
> I have posted the presentation that we will be going through on the
> Kato Wiki.
> You can link to it here:
> http://cwiki.apache.org/confluence/display/KATO/API+Walkthrough
> The recording will be made available in the same place, at the very
> least the transcription and notes will be there.
>
> If you are unable to join the meeting on Sametime Unyte here:
> https://www.webdialogs.com/join/ you will should be able to go through
> the presentation from the wiki.
>
> Speak to you at 1500.
>
> Stuart
>
>
>
RE: Conference call
Posted by "Bobrovsky, Konstantin S" <ko...@intel.com>.
> - I will provide more explanations about my comment on derived pointer
> support early next week.
First, let me describe what I mean by "derived pointer" (might be well-known term to those who worked with the Hotspot JVM)
This is a pointer which is logically bound to some "base" java object. For example, pointer to a memory location holding an array element (regardless of the element type) is a derived pointer, and the array object itself is the base object. Derived pointers are "produced" by JIT-ed code (e.g. to quickly access array elements, current element's address might be kept in a register), and during GC their value must be updated whenever the GC moves the base object (basically, derived pointer value should change by the same number the address of the base object changes). To support that, derived pointer is reported to GC as "live" always together with its base (whose live range is sometimes artificially stretched to match one of the derived pointer). At least two VMs I worked with employ this concept: Hotspot and Harmony.
My comment was whether it is possible to find/identify live derived pointers + bases through a JavaStackFrame instance. It might be interesting for an engineer analyzing a post-mortem dump to learn where the derived pointers and their bases are for the same reasons as it might be interesting for him to find "usual" heap roots.
Hope this helps,
Konst
Intel Novosibirsk
Closed Joint Stock Company Intel A/O
Registered legal address: Krylatsky Hills Business Park,
17 Krylatskaya Str., Bldg 4, Moscow 121614,
Russian Federation
-----Original Message-----
From: Bobrovsky, Konstantin S
Sent: Friday, April 24, 2009 11:13 PM
To: 'kato-spec@incubator.apache.org'; kato-dev@incubator.apache.org
Subject: RE: Conference call
Hello all,
Quick follow up to the meeting:
- JavaMethod
In many VMs each method may have multiple compiled versions (even co-existing at the same time). I think the API should provide access to all of them. Will client be able to access all of them via getCompiledSections()?
- ImageStackFrame
It would be good if the API would support architectures with additional register stack (such as Itanium). E.g. through an additional pointer to the base of the register stack frame.
- I will provide more explanations about my comment on derived pointer support early next week.
Thanks,
Konst
Intel Novosibirsk
Closed Joint Stock Company Intel A/O
Registered legal address: Krylatsky Hills Business Park,
17 Krylatskaya Str., Bldg 4, Moscow 121614,
Russian Federation
-----Original Message-----
From: Stuart Monteith [mailto:stukato@stoo.me.uk]
Sent: Friday, April 24, 2009 8:32 PM
To: kato-dev@incubator.apache.org; kato-spec@incubator.apache.org
Subject: Conference call
Hello all,
I have posted the presentation that we will be going through on the
Kato Wiki.
You can link to it here:
http://cwiki.apache.org/confluence/display/KATO/API+Walkthrough
The recording will be made available in the same place, at the very
least the transcription and notes will be there.
If you are unable to join the meeting on Sametime Unyte here:
https://www.webdialogs.com/join/ you will should be able to go through
the presentation from the wiki.
Speak to you at 1500.
Stuart
RE: Conference call
Posted by "Bobrovsky, Konstantin S" <ko...@intel.com>.
Hello all,
Quick follow up to the meeting:
- JavaMethod
In many VMs each method may have multiple compiled versions (even co-existing at the same time). I think the API should provide access to all of them. Will client be able to access all of them via getCompiledSections()?
- ImageStackFrame
It would be good if the API would support architectures with additional register stack (such as Itanium). E.g. through an additional pointer to the base of the register stack frame.
- I will provide more explanations about my comment on derived pointer support early next week.
Thanks,
Konst
Intel Novosibirsk
Closed Joint Stock Company Intel A/O
Registered legal address: Krylatsky Hills Business Park,
17 Krylatskaya Str., Bldg 4, Moscow 121614,
Russian Federation
-----Original Message-----
From: Stuart Monteith [mailto:stukato@stoo.me.uk]
Sent: Friday, April 24, 2009 8:32 PM
To: kato-dev@incubator.apache.org; kato-spec@incubator.apache.org
Subject: Conference call
Hello all,
I have posted the presentation that we will be going through on the
Kato Wiki.
You can link to it here:
http://cwiki.apache.org/confluence/display/KATO/API+Walkthrough
The recording will be made available in the same place, at the very
least the transcription and notes will be there.
If you are unable to join the meeting on Sametime Unyte here:
https://www.webdialogs.com/join/ you will should be able to go through
the presentation from the wiki.
Speak to you at 1500.
Stuart
RE: Conference call
Posted by "Bobrovsky, Konstantin S" <ko...@intel.com>.
> - I will provide more explanations about my comment on derived pointer
> support early next week.
First, let me describe what I mean by "derived pointer" (might be well-known term to those who worked with the Hotspot JVM)
This is a pointer which is logically bound to some "base" java object. For example, pointer to a memory location holding an array element (regardless of the element type) is a derived pointer, and the array object itself is the base object. Derived pointers are "produced" by JIT-ed code (e.g. to quickly access array elements, current element's address might be kept in a register), and during GC their value must be updated whenever the GC moves the base object (basically, derived pointer value should change by the same number the address of the base object changes). To support that, derived pointer is reported to GC as "live" always together with its base (whose live range is sometimes artificially stretched to match one of the derived pointer). At least two VMs I worked with employ this concept: Hotspot and Harmony.
My comment was whether it is possible to find/identify live derived pointers + bases through a JavaStackFrame instance. It might be interesting for an engineer analyzing a post-mortem dump to learn where the derived pointers and their bases are for the same reasons as it might be interesting for him to find "usual" heap roots.
Hope this helps,
Konst
Intel Novosibirsk
Closed Joint Stock Company Intel A/O
Registered legal address: Krylatsky Hills Business Park,
17 Krylatskaya Str., Bldg 4, Moscow 121614,
Russian Federation
-----Original Message-----
From: Bobrovsky, Konstantin S
Sent: Friday, April 24, 2009 11:13 PM
To: 'kato-spec@incubator.apache.org'; kato-dev@incubator.apache.org
Subject: RE: Conference call
Hello all,
Quick follow up to the meeting:
- JavaMethod
In many VMs each method may have multiple compiled versions (even co-existing at the same time). I think the API should provide access to all of them. Will client be able to access all of them via getCompiledSections()?
- ImageStackFrame
It would be good if the API would support architectures with additional register stack (such as Itanium). E.g. through an additional pointer to the base of the register stack frame.
- I will provide more explanations about my comment on derived pointer support early next week.
Thanks,
Konst
Intel Novosibirsk
Closed Joint Stock Company Intel A/O
Registered legal address: Krylatsky Hills Business Park,
17 Krylatskaya Str., Bldg 4, Moscow 121614,
Russian Federation
-----Original Message-----
From: Stuart Monteith [mailto:stukato@stoo.me.uk]
Sent: Friday, April 24, 2009 8:32 PM
To: kato-dev@incubator.apache.org; kato-spec@incubator.apache.org
Subject: Conference call
Hello all,
I have posted the presentation that we will be going through on the
Kato Wiki.
You can link to it here:
http://cwiki.apache.org/confluence/display/KATO/API+Walkthrough
The recording will be made available in the same place, at the very
least the transcription and notes will be there.
If you are unable to join the meeting on Sametime Unyte here:
https://www.webdialogs.com/join/ you will should be able to go through
the presentation from the wiki.
Speak to you at 1500.
Stuart