On Fri, Apr 17, 2015 at 10:07 AM, Subhro Paul <subhro.p...@tcs.com> wrote:
> From: Ameer Mawia <ameer.ma...@gmail.com> > To: Tomcat Users List <users@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 <dcker...@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-unsubscr...@tomcat.apache.org > > For additional commands, e-mail: users-h...@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
