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Posted to users@tomcat.apache.org by Subhro Paul <su...@tcs.com> on 2015/04/17 14:32:33 UTC
GC Issue on Tomcat6
Hi Team,
For our client website we have two Tomcat servers. Both servers are having
same configuration which is 16GB RAM, 8CPUS and Linux 6.5 OS. Tomcat 6 and
JAVA 6 are installed in both systems.
Yesterday, using Jconsole we observed that frequency of GC on one server
was very high which was 5 GC hit per Minute and on other server it was 1
GC hit per 3 Minutes. But today we observed that on both of the servers GC
frequency is same.
Is this a know secnario or the server is facing any issue?
Thanks & Regards
Subhro Paul
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Re: GC Issue on Tomcat6
Posted by Ameer Mawia <am...@gmail.com>.
On Fri, Apr 17, 2015 at 10:07 AM, Subhro Paul <su...@tcs.com> wrote:
> From: Ameer Mawia <am...@gmail.com>
> To: Tomcat Users List <us...@tomcat.apache.org>
> Date: 04/17/2015 06:29 PM
> Subject: Re: GC Issue on Tomcat6
>
>
>
> http://ca.linkedin.com/in/ameermawia
> Toronto, ON
> Phone:647-262-4380
>
> On Fri, Apr 17, 2015 at 8:47 AM, David kerber <dc...@verizon.net>
> wrote:
>
> > On 4/17/2015 8:32 AM, Subhro Paul wrote:
> >
> >> Hi Team,
> >>
> >> For our client website we have two Tomcat servers. Both servers are
> having
> >> same configuration which is 16GB RAM, 8CPUS and Linux 6.5 OS. Tomcat 6
> and
> >> JAVA 6 are installed in both systems.
> >>
> >> Yesterday, using Jconsole we observed that frequency of GC on one
> server
> >> was very high which was 5 GC hit per Minute and on other server it was
> 1
> >> GC hit per 3 Minutes. But today we observed that on both of the servers
> GC
> >> frequency is same.
> >>
> >> Garbage Collection in Oracle Hot spot JVM takes place in generational
> manner. GC on young generation is invoked much more frequently, while Full
> GC is invoked once in a while. In any case, frequency is much higher than
> what you have mentioned.
>
> I'm not sure which GC(Young/Full) you are talking about? What pattern of
> GC
> you have earlier observed?
>
> > Is this a know secnario or the server is facing any issue?
> >>
> >
> > GC issue has nothing to do with Tomcat per say. It is the memory
> footprint
> of your application which will dictate GC behavior.
>
> In any case, if your application is facing some memory bottle-neck, it is
> better to pay attention on the percentage your JVM is spending in GCing
> your application. If that percentage is very high, say ~90%, that means
> your application is facing sever memory constrain, your application is
> almost stalled as JVM has been trying very high to recover some space.
> Most
> probably in that case, your JVM will die throwing OOM error in sometime.
>
>
> > It was probably just receiving more traffic and/or doing more work of
> some
> > other kind.
> >
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> > For additional commands, e-mail: users-help@tomcat.apache.org
> >
> >
>
>
> Dear Ameer,
>
I am talking about Young GC which is "PS Scavenge" for both of the
> servers. Full GC was Running 1/Hour. Can you please assist how to check
> the % of memory utilization by GC through JConsole or any other process.
Subhro, please reply inline. People prefer that way here. It makes reading
the thread easier.
I was talking about percentage utilization of CPU Time by GC Threads.
Getting % Memory usage is also very helpful.
There is a number of way to check Memory utilization, stats:
- JConsole Memory tab.
- Console output. You will have to turn on the JVM flag to dump these
details.
- -XX:+PrintGCDetails -- This also give time spent in a particular GC
operation.
- Thread dump( Kill -3 Unix machine)
Also, you can get some fine tuned information about time usage by your
application threads, using these flags:
- -XX:+PrintGCApplicationConcurrentTime
- -XX:+PrintGCApplicationStoppedTime
Out of curiosity, how did you get this information " Full GC was Running
1/Hour".
I guess that is too few run.
>
>
Thanks & Regards,
> Subhro Paul
> =====-----=====-----=====
> Notice: The information contained in this e-mail
> message and/or attachments to it may contain
> confidential or privileged information. If you are
> not the intended recipient, any dissemination, use,
> review, distribution, printing or copying of the
> information contained in this e-mail message
> and/or attachments to it are strictly prohibited. If
> you have received this communication in error,
> please notify us by reply e-mail or telephone and
> immediately and permanently delete the message
> and any attachments. Thank you
>
>
>
--
http://ca.linkedin.com/in/ameermawia
Toronto, ON
Re: GC Issue on Tomcat6
Posted by Subhro Paul <su...@tcs.com>.
From: Ameer Mawia <am...@gmail.com>
To: Tomcat Users List <us...@tomcat.apache.org>
Date: 04/17/2015 06:29 PM
Subject: Re: GC Issue on Tomcat6
http://ca.linkedin.com/in/ameermawia
Toronto, ON
Phone:647-262-4380
On Fri, Apr 17, 2015 at 8:47 AM, David kerber <dc...@verizon.net>
wrote:
> On 4/17/2015 8:32 AM, Subhro Paul wrote:
>
>> Hi Team,
>>
>> For our client website we have two Tomcat servers. Both servers are
having
>> same configuration which is 16GB RAM, 8CPUS and Linux 6.5 OS. Tomcat 6
and
>> JAVA 6 are installed in both systems.
>>
>> Yesterday, using Jconsole we observed that frequency of GC on one
server
>> was very high which was 5 GC hit per Minute and on other server it was
1
>> GC hit per 3 Minutes. But today we observed that on both of the servers
GC
>> frequency is same.
>>
>> Garbage Collection in Oracle Hot spot JVM takes place in generational
manner. GC on young generation is invoked much more frequently, while Full
GC is invoked once in a while. In any case, frequency is much higher than
what you have mentioned.
I'm not sure which GC(Young/Full) you are talking about? What pattern of
GC
you have earlier observed?
> Is this a know secnario or the server is facing any issue?
>>
>
> GC issue has nothing to do with Tomcat per say. It is the memory
footprint
of your application which will dictate GC behavior.
In any case, if your application is facing some memory bottle-neck, it is
better to pay attention on the percentage your JVM is spending in GCing
your application. If that percentage is very high, say ~90%, that means
your application is facing sever memory constrain, your application is
almost stalled as JVM has been trying very high to recover some space.
Most
probably in that case, your JVM will die throwing OOM error in sometime.
> It was probably just receiving more traffic and/or doing more work of
some
> other kind.
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> For additional commands, e-mail: users-help@tomcat.apache.org
>
>
Dear Ameer,
I am talking about Young GC which is "PS Scavenge" for both of the
servers. Full GC was Running 1/Hour. Can you please assist how to check
the % of memory utilization by GC through JConsole or any other process.
Thanks & Regards,
Subhro Paul
=====-----=====-----=====
Notice: The information contained in this e-mail
message and/or attachments to it may contain
confidential or privileged information. If you are
not the intended recipient, any dissemination, use,
review, distribution, printing or copying of the
information contained in this e-mail message
and/or attachments to it are strictly prohibited. If
you have received this communication in error,
please notify us by reply e-mail or telephone and
immediately and permanently delete the message
and any attachments. Thank you
Re: GC Issue on Tomcat6
Posted by Ameer Mawia <am...@gmail.com>.
http://ca.linkedin.com/in/ameermawia
Toronto, ON
Phone:647-262-4380
On Fri, Apr 17, 2015 at 8:47 AM, David kerber <dc...@verizon.net> wrote:
> On 4/17/2015 8:32 AM, Subhro Paul wrote:
>
>> Hi Team,
>>
>> For our client website we have two Tomcat servers. Both servers are having
>> same configuration which is 16GB RAM, 8CPUS and Linux 6.5 OS. Tomcat 6 and
>> JAVA 6 are installed in both systems.
>>
>> Yesterday, using Jconsole we observed that frequency of GC on one server
>> was very high which was 5 GC hit per Minute and on other server it was 1
>> GC hit per 3 Minutes. But today we observed that on both of the servers GC
>> frequency is same.
>>
>> Garbage Collection in Oracle Hot spot JVM takes place in generational
manner. GC on young generation is invoked much more frequently, while Full
GC is invoked once in a while. In any case, frequency is much higher than
what you have mentioned.
I'm not sure which GC(Young/Full) you are talking about? What pattern of GC
you have earlier observed?
> Is this a know secnario or the server is facing any issue?
>>
>
> GC issue has nothing to do with Tomcat per say. It is the memory footprint
of your application which will dictate GC behavior.
In any case, if your application is facing some memory bottle-neck, it is
better to pay attention on the percentage your JVM is spending in GCing
your application. If that percentage is very high, say ~90%, that means
your application is facing sever memory constrain, your application is
almost stalled as JVM has been trying very high to recover some space. Most
probably in that case, your JVM will die throwing OOM error in sometime.
> It was probably just receiving more traffic and/or doing more work of some
> other kind.
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: users-unsubscribe@tomcat.apache.org
> For additional commands, e-mail: users-help@tomcat.apache.org
>
>
Re: GC Issue on Tomcat6
Posted by David kerber <dc...@verizon.net>.
On 4/17/2015 8:32 AM, Subhro Paul wrote:
> Hi Team,
>
> For our client website we have two Tomcat servers. Both servers are having
> same configuration which is 16GB RAM, 8CPUS and Linux 6.5 OS. Tomcat 6 and
> JAVA 6 are installed in both systems.
>
> Yesterday, using Jconsole we observed that frequency of GC on one server
> was very high which was 5 GC hit per Minute and on other server it was 1
> GC hit per 3 Minutes. But today we observed that on both of the servers GC
> frequency is same.
>
> Is this a know secnario or the server is facing any issue?
It was probably just receiving more traffic and/or doing more work of
some other kind.
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