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Posted to users@tomcat.apache.org by Peter Irbizon <pe...@gmail.com> on 2015/02/24 13:33:34 UTC
when idle tomcat runs on 3.9% CPU
Hello,
I would like to know if it is normal that tomcat7 runs on 3.9% CPU when
idle? I saw all other processes are at 0%, only tomcat7 is always at least
3.9%.
Re: when idle tomcat runs on 3.9% CPU
Posted by "John D. Ament" <jo...@apache.org>.
When you say idle, is there an application deployed to tomcat, or is it
just the bare app server with nothing deployed?
On Tue Feb 24 2015 at 7:35:31 AM Peter Irbizon <pe...@gmail.com>
wrote:
> Hello,
> I would like to know if it is normal that tomcat7 runs on 3.9% CPU when
> idle? I saw all other processes are at 0%, only tomcat7 is always at least
> 3.9%.
>
Re: when idle tomcat runs on 3.9% CPU
Posted by David kerber <dc...@verizon.net>.
On 2/27/2015 9:14 AM, Caldarale, Charles R wrote:
>> From: Peter Irbizon [mailto:peterirbizon@gmail.com]
>> Subject: Re: when idle tomcat runs on 3.9% CPU
>
>> 1. It is the latest Debian on Raspberry Pi (aka Raspbian). Hardware is
>> Raspberry Pi.
>
> That would seem to fit Chris' postulation pretty much exactly:
>
>>> There is also the question of "3.9% of what"? If it's a slow, single core
>>> machine, it's a lot more likely that TC might use 3% of it, than it is if
>>> it's a 16-core 3.5GHz server.
Yup. That's probably what the background listening threads take on that
hardware and OS combination. Also consider that the OS probably hasn't
had the amount of optimization on RP that it has on desktop or server
hardware.
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Re: when idle tomcat runs on 3.9% CPU
Posted by Rainer Jung <ra...@kippdata.de>.
Am 27.02.2015 um 18:07 schrieb Christopher Schultz:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> Peter,
>
> On 2/27/15 11:21 AM, Peter Irbizon wrote:
>> Hi Chris, here are my dumps
>> http://www.filedropper.com/jvmthreaddump. It looks like it has
>> something to do with memcached.
>
> There are a bunch of RUNNABLE threads, but sometimes the term
> "RUNNABLE" in a Java thread dump doesn't actually mean "taking CPU
> time right now". For example, the "main" thread is RUNNABLE but it's
> waiting on accepting a socket connection (for a SHUTDOWN command) and
> so it's effectively blocked, taking zero CPU time.
>
> I'm not entirely sure what the Memcached threads actually do, but I
> think they are in a similar situation: waiting for code to request
> some communication with Memcached.
I agree, hard to say from those dumps what's consuming the CPU, could be
even GC threads. It's easier if threads are actually doing something,
not just hanging around and waiting for work.
If you have commandline access, use
top -H -p PID
to show the list of threads of your process (replace PID by the process
ID of your Java process) and check, what the thread numbers that are
active on the CPU are. Hopefully it is only a few threads. Then take the
thread number and translate it from decimal to hexadecimal and look for
it in the header lines of your thread dumps.
Example:
The thread
"Memcached IO over {MemcachedConnection to localhost/127.0.0.1:11215}"
prio=10 tid=0x025558d8 nid=0x34d3 runnable [0x9f4fe000]
from the dump will be shown on some Linuxes in top -H as thread id
0x34d3 = 13523
on others as
0x025558d8 = 39147736
If the thread ID doesn't occur in the thread dump at all, then it is
native threads (unlikely but possible).
Regards,
Rainer
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Re: when idle tomcat runs on 3.9% CPU
Posted by Christopher Schultz <ch...@christopherschultz.net>.
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Hash: SHA256
Peter,
On 2/27/15 11:21 AM, Peter Irbizon wrote:
> Hi Chris, here are my dumps
> http://www.filedropper.com/jvmthreaddump. It looks like it has
> something to do with memcached.
There are a bunch of RUNNABLE threads, but sometimes the term
"RUNNABLE" in a Java thread dump doesn't actually mean "taking CPU
time right now". For example, the "main" thread is RUNNABLE but it's
waiting on accepting a socket connection (for a SHUTDOWN command) and
so it's effectively blocked, taking zero CPU time.
I'm not entirely sure what the Memcached threads actually do, but I
think they are in a similar situation: waiting for code to request
some communication with Memcached.
- -chris
> 2015-02-27 16:46 GMT+01:00 Christopher Schultz
> <chris@christopherschultz.net
>> :
>
> Peter,
>
> On 2/27/15 10:41 AM, Peter Irbizon wrote:
>>>> 2015-02-27 16:32 GMT+02:00 Christopher Schultz
>>>> <chris@christopherschultz.net
>>>>> : How much memory is in this thing?
>>>>
>>>> I have one with 700 MHz ARM1176JZ, 512MB RAM (model B). By
>>>> the way it is working pretty nice :) I tried just to figure
>>>> it out why only tomcat7 consumes some CPU when all other
>>>> services are at 0%.
>
> Can you get a shell running on it? If so, take thread dumps of the
> JVM process: that will tell you (or us) what's going on.
>
> You can adjust the background thread's timing, but it's pretty
> innocuous.
>
> -chris
>>
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Re: when idle tomcat runs on 3.9% CPU
Posted by Peter Irbizon <pe...@gmail.com>.
Hi Chris,
here are my dumps http://www.filedropper.com/jvmthreaddump. It looks like
it has something to do with memcached.
2015-02-27 16:46 GMT+01:00 Christopher Schultz <chris@christopherschultz.net
>:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> Peter,
>
> On 2/27/15 10:41 AM, Peter Irbizon wrote:
> > 2015-02-27 16:32 GMT+02:00 Christopher Schultz
> > <chris@christopherschultz.net
> >> : How much memory is in this thing?
> >
> > I have one with 700 MHz ARM1176JZ, 512MB RAM (model B). By the way
> > it is working pretty nice :) I tried just to figure it out why only
> > tomcat7 consumes some CPU when all other services are at 0%.
>
> Can you get a shell running on it? If so, take thread dumps of the JVM
> process: that will tell you (or us) what's going on.
>
> You can adjust the background thread's timing, but it's pretty innocuous.
>
> - -chris
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Re: when idle tomcat runs on 3.9% CPU
Posted by Christopher Schultz <ch...@christopherschultz.net>.
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
Peter,
On 2/27/15 10:41 AM, Peter Irbizon wrote:
> 2015-02-27 16:32 GMT+02:00 Christopher Schultz
> <chris@christopherschultz.net
>> : How much memory is in this thing?
>
> I have one with 700 MHz ARM1176JZ, 512MB RAM (model B). By the way
> it is working pretty nice :) I tried just to figure it out why only
> tomcat7 consumes some CPU when all other services are at 0%.
Can you get a shell running on it? If so, take thread dumps of the JVM
process: that will tell you (or us) what's going on.
You can adjust the background thread's timing, but it's pretty innocuous.
- -chris
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Re: when idle tomcat runs on 3.9% CPU
Posted by Peter Irbizon <pe...@gmail.com>.
2015-02-27 16:32 GMT+02:00 Christopher Schultz <chris@christopherschultz.net
>:
> How much memory is in this thing?
I have one with 700 MHz ARM1176JZ, 512MB RAM (model B). By the way it is
working pretty nice :) I tried just to figure it out why only tomcat7
consumes some CPU when all other services are at 0%.
Re: when idle tomcat runs on 3.9% CPU
Posted by Антон Мацюк <de...@gmail.com>.
2015-02-27 16:32 GMT+02:00 Christopher Schultz <ch...@christopherschultz.net>:
> How much memory is in this thing?
It varies, 256MB or 512MB for model B, if I remember it right.
Have one serving DHCP at home :)
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Re: when idle tomcat runs on 3.9% CPU
Posted by Christopher Schultz <ch...@christopherschultz.net>.
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Hash: SHA256
Chuck,
On 2/27/15 9:14 AM, Caldarale, Charles R wrote:
>> From: Peter Irbizon [mailto:peterirbizon@gmail.com] Subject: Re:
>> when idle tomcat runs on 3.9% CPU
>
>> 1. It is the latest Debian on Raspberry Pi (aka Raspbian).
>> Hardware is Raspberry Pi.
>
> That would seem to fit Chris' postulation pretty much exactly:
It was David's postulation, but honestly... I'm impressed that someone
got Tomcat running on a Raspberry Pi. When I think "Raspberry Pi", I
must admit that "Java" isn't the first solution that comes to mind.
How much memory is in this thing?
- -chris
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RE: when idle tomcat runs on 3.9% CPU
Posted by "Caldarale, Charles R" <Ch...@unisys.com>.
> From: Peter Irbizon [mailto:peterirbizon@gmail.com]
> Subject: Re: when idle tomcat runs on 3.9% CPU
> 1. It is the latest Debian on Raspberry Pi (aka Raspbian). Hardware is
> Raspberry Pi.
That would seem to fit Chris' postulation pretty much exactly:
> > There is also the question of "3.9% of what"? If it's a slow, single core
> > machine, it's a lot more likely that TC might use 3% of it, than it is if
> > it's a 16-core 3.5GHz server.
- Chuck
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Re: when idle tomcat runs on 3.9% CPU
Posted by Peter Irbizon <pe...@gmail.com>.
Hello again, my answers to questions:
1. It is the latest Debian on Raspberry Pi (aka Raspbian). Hardware is
Raspberry Pi.
2. Maybe "idle" is not the best word in my case. Yes, app is deployed on
server but it is just for this: wait for incoming data over POST and the
save it to database. No traffic currently. (so it should not do anything
else)
Tomcat is 7. Apache Tomcat/7.0.28, JVM 1.7.0_25-b30
3. Profiler - I am newbie, but I will try to google it and run it.
I see always at least 3.9% CPU in top.
2015-02-24 16:34 GMT+01:00 David kerber <dc...@verizon.net>:
> On 2/24/2015 10:16 AM, Christopher Schultz wrote:
>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA256
>>
>> Daniel,
>>
>> On 2/24/15 8:01 AM, Daniel Mikusa wrote:
>>
>>> On Tue, Feb 24, 2015 at 7:33 AM, Peter Irbizon
>>> <pe...@gmail.com> wrote:
>>>
>>> Hello, I would like to know if it is normal that tomcat7 runs on
>>>> 3.9% CPU when idle? I saw all other processes are at 0%, only
>>>> tomcat7 is always at least 3.9%.
>>>>
>>>>
>>> 1.) What's your system like? How many CPUs / cores? Is it a VM or
>>> hardware? What is the specific version of Tomcat? of Java? What
>>> OS are you running?
>>>
>>> 2.) How are you determining it's idle? As John mention, do you
>>> have any apps deployed? Do you know if traffic is hitting the
>>> server?
>>>
>>> 3.) Can you run a profiler and attach it to Tomcat? It'll tell
>>> you what's happening inside the JVM.
>>>
>>
>> 4. Take a few thread dumps to see what the JVM threads are doing.
>>
>> When truly idle (i.e. no requests are being processed), Tomcat runs a
>> maintenance thread that performs some background tasks, but that runs
>> about once every 60 seconds and does very little, depending on what
>> you have configured.
>>
>> So unless you are seeing that thread specifically running at its
>> interval, Tomcat's threads are totally blocked waiting on various
>> events to occur (like an I/O event for an incoming request, or waiting
>> for a timeout to perform that maintenance).
>>
>> On a dev server, I just checked and my Tomcat processes go down to 0.0
>> CPU as measured by top when they aren't "doing" anything.
>>
>
> There is also the question of "3.9% of what"? If it's a slow, single core
> machine, it's a lot more likely that TC might use 3% of it, than it is if
> it's a 16-core 3.5GHz server.
>
>
>
>> The thread dumps will likely tell the story.
>>
>> - -chris
>>
>
>
>
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Re: when idle tomcat runs on 3.9% CPU
Posted by David kerber <dc...@verizon.net>.
On 2/24/2015 10:16 AM, Christopher Schultz wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> Daniel,
>
> On 2/24/15 8:01 AM, Daniel Mikusa wrote:
>> On Tue, Feb 24, 2015 at 7:33 AM, Peter Irbizon
>> <pe...@gmail.com> wrote:
>>
>>> Hello, I would like to know if it is normal that tomcat7 runs on
>>> 3.9% CPU when idle? I saw all other processes are at 0%, only
>>> tomcat7 is always at least 3.9%.
>>>
>>
>> 1.) What's your system like? How many CPUs / cores? Is it a VM or
>> hardware? What is the specific version of Tomcat? of Java? What
>> OS are you running?
>>
>> 2.) How are you determining it's idle? As John mention, do you
>> have any apps deployed? Do you know if traffic is hitting the
>> server?
>>
>> 3.) Can you run a profiler and attach it to Tomcat? It'll tell
>> you what's happening inside the JVM.
>
> 4. Take a few thread dumps to see what the JVM threads are doing.
>
> When truly idle (i.e. no requests are being processed), Tomcat runs a
> maintenance thread that performs some background tasks, but that runs
> about once every 60 seconds and does very little, depending on what
> you have configured.
>
> So unless you are seeing that thread specifically running at its
> interval, Tomcat's threads are totally blocked waiting on various
> events to occur (like an I/O event for an incoming request, or waiting
> for a timeout to perform that maintenance).
>
> On a dev server, I just checked and my Tomcat processes go down to 0.0
> CPU as measured by top when they aren't "doing" anything.
There is also the question of "3.9% of what"? If it's a slow, single
core machine, it's a lot more likely that TC might use 3% of it, than it
is if it's a 16-core 3.5GHz server.
>
> The thread dumps will likely tell the story.
>
> - -chris
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Re: when idle tomcat runs on 3.9% CPU
Posted by Christopher Schultz <ch...@christopherschultz.net>.
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
Daniel,
On 2/24/15 8:01 AM, Daniel Mikusa wrote:
> On Tue, Feb 24, 2015 at 7:33 AM, Peter Irbizon
> <pe...@gmail.com> wrote:
>
>> Hello, I would like to know if it is normal that tomcat7 runs on
>> 3.9% CPU when idle? I saw all other processes are at 0%, only
>> tomcat7 is always at least 3.9%.
>>
>
> 1.) What's your system like? How many CPUs / cores? Is it a VM or
> hardware? What is the specific version of Tomcat? of Java? What
> OS are you running?
>
> 2.) How are you determining it's idle? As John mention, do you
> have any apps deployed? Do you know if traffic is hitting the
> server?
>
> 3.) Can you run a profiler and attach it to Tomcat? It'll tell
> you what's happening inside the JVM.
4. Take a few thread dumps to see what the JVM threads are doing.
When truly idle (i.e. no requests are being processed), Tomcat runs a
maintenance thread that performs some background tasks, but that runs
about once every 60 seconds and does very little, depending on what
you have configured.
So unless you are seeing that thread specifically running at its
interval, Tomcat's threads are totally blocked waiting on various
events to occur (like an I/O event for an incoming request, or waiting
for a timeout to perform that maintenance).
On a dev server, I just checked and my Tomcat processes go down to 0.0
CPU as measured by top when they aren't "doing" anything.
The thread dumps will likely tell the story.
- -chris
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Re: when idle tomcat runs on 3.9% CPU
Posted by Daniel Mikusa <dm...@pivotal.io>.
On Tue, Feb 24, 2015 at 7:33 AM, Peter Irbizon <pe...@gmail.com>
wrote:
> Hello,
> I would like to know if it is normal that tomcat7 runs on 3.9% CPU when
> idle? I saw all other processes are at 0%, only tomcat7 is always at least
> 3.9%.
>
1.) What's your system like? How many CPUs / cores? Is it a VM or
hardware? What is the specific version of Tomcat? of Java? What OS are
you running?
2.) How are you determining it's idle? As John mention, do you have any
apps deployed? Do you know if traffic is hitting the server?
3.) Can you run a profiler and attach it to Tomcat? It'll tell you what's
happening inside the JVM.
Dan