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From Edson Richter <edsonrich...@hotmail.com>
Subject Re: Help in diagnosing server unresponsiveness
Date Wed, 20 Feb 2013 12:03:55 GMT
AFAIK, as best practice is recommended that if you have dedicated 
server, let -Xms as close as possible to -Xmx to avoid extra effort in 
releasing memory.

I remember to read this information as recommended by Oracle (JRockit) 
and IBM (WebSphere) documentation (unfortunately, I don't have the 
papers link right here).

Regards,

Edson

Em 20/02/2013 05:52, Zoran Avtarovski escreveu:
> Hi Guys,
>
> It's been a while but the nature of this problem means it may be a while
> between crashes. But we just had a big one which hung the system and
> required a reboot.
>
> I have changed the tomcat options as follows inline with all the advice
> and material I read to be as follows:
>
> -server -Xms1460m -Xmx11460m -Djava.awt.headless=true
> -XX:+UseCompressedOops -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode
> -XX:MaxPermSize=512M -XX:NewSize=4500m -XX:+CMSClassUnloadingEnabled
> -XX:+UseConcMarkSweepGC -XX:-UseGCOverheadLimit
> -XX:CMSInitiatingOccupancyFraction=80 -verbose:gc -XX:+PrintGCDetails
> -XX:+PrintGCTimeStamps -Xloggc:/usr/local/tomcat/logs/gc.log
>
>
> The garbage collection log had the following details just prior to the
> crash:
>
> 4163.757: [GC [1 CMS-initial-mark: 0K(5376K)] 1834200K(4152576K),
> 1.9237250 secs] [Times: user=1.92 sys=0.00, real=1.92 secs]
> 4165.682: [CMS-concurrent-mark-start]
> 4165.834: [CMS-concurrent-mark: 0.152/0.152 secs] [Times: user=0.15
> sys=0.00, real=0.16 secs]
> 4165.834: [CMS-concurrent-preclean-start]
> 4165.849: [CMS-concurrent-preclean: 0.015/0.015 secs] [Times: user=0.01
> sys=0.00, real=0.01 secs]
> 4165.849: [CMS-concurrent-abortable-preclean-start]
>   CMS: abort preclean due to time 4171.285:
> [CMS-concurrent-abortable-preclean: 5.035/5.436 secs] [Times: user=5.05
> sys=0.00, real=5.44 secs]
> 4171.285: [GC[YG occupancy: 1834200 K (4147200 K)]4171.286: [Rescan
> (parallel) , 1.5184720 secs]4172.804: [weak refs processing, 0.0001420
> secs]4172.804: [class unloading, 0.0118860 secs]4172.816: [scrub symbol &
> string tables, 0.0141570 secs] [1 CMS-remark: 0K(5376K)]
> 1834200K(4152576K), 1.5484470 secs]
>
>
>
> 				
> 			
> 		
> 	
> And the JavaMelody monitoring indicated the crash occurred at the same
> time as garbage collection took place. Basically the Garbage collector
> time chart peaked at 20 and ran for about 15minutes.
>
>
> I has a look at the garbage collector chart over a longer period and when
> the collector runs more frequently it appears to be more stable.
>
> Any advice on where to go next?
>
>
> Z.
>
>
>
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>
>


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