GC Tuning

[Poonam Bajaj Parhar]

Hello Joseph,

 From the GC logs, all the G1 evacuation pauses are under 100ms of pause 
time goal. However, there are System.gc() invoked Full GCs that are 
taking longer time.

/62.730: [GC pause (young), 0.02510300 secs]
...
64.287: [Full GC (System.gc()) 175M->98M(2048M), 0.2183040 secs]
  [Times: user=0.26 sys=0.01, real=0.22 secs]
64.509: [Full GC (System.gc()) 98M->98M(2048M), 0.1928990 secs]
  [Times: user=0.24 sys=0.00, real=0.20 secs]
64.704: [Full GC (System.gc()) 98M->98M(2048M), 0.1893760 secs]
  [Times: user=0.25 sys=0.00, real=0.19 secs]
64.896: [Full GC (System.gc()) 98M->97M(2048M), 0.2001590 secs]
  [Times: user=0.25 sys=0.00, real=0.20 secs]
65.098: [Full GC (System.gc()) 98M->97M(2048M), 0.1874640 secs]
  [Times: user=0.24 sys=0.00, real=0.19 secs]
66.818: [Full GC (System.gc()) 185M->99M(2048M), 0.2137830 secs]
  [Times: user=0.27 sys=0.00, real=0.22 secs]//
73.240: [GC pause (young), 0.02516600 secs]/

Please check your application code to see if these System.gc() 
invocations are intentional. You may also disable these using 
-XX:+DisableExplicitGC option.

Thanks,
Poonam

On 9/17/2015 6:02 AM, Joseph wrote:
>
> Hi ,
>
> I am Joseph. I am trying to tune performance of  our server .I run 
> server with following g1 gc options.
>
> Maximum heap allocated to server is 5GB.
>
> " -XX:+UseG1GC -XX:MaxGCPauseMillis=100 -XX:ParallelGCThreads=4 
> -XX:InitiatingHeapOccupancyPercent=65 -XX:+ParallelRefProcEnabled 
> -XX:-ResizePLAB -Xloggc:/var/log/hbase/gc-hbase.log 
> -XX:+PrintGCDetails -XX:+PrintAdaptiveSizePolicy -XX:+PrintGCTimeStamps"
>
> The gc logs resulted with above gc flags are attached with the 
> mail.How to reduce garbage pause time in our server.
>
> Thank you for your valuble time
>
> *Regards,*
>
> *Joseph*
>
>
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