G1 GC Tuning parameters

[Shawn Heisey]

On 8/4/2018 1:58 AM, Narasimha C Achi wrote:
> Please find attached logs. java web services are deployed in these
> servers.
>
> Attachment 1: shows to-space exhausted and allocation failure
>
> Attachment2: Log GC Pauses.
>

I uploaded your zipfile to http://gceasy.io for analysis.

The first thing it says is that you have explicitly configured the sizes
of the different generations.  With G1, it is recommended to not
explicitly set those sizes.  G1 will adjust the sizes as it runs for
optimal operation.

One of your logs shows these commandline options:

CommandLine flags: -XX:CICompilerCount=4 -XX:ConcGCThreads=2
-XX:G1HeapRegionSize=2097152 -XX:GCLogFileSize=10485760
-XX:InitialHeapSize=6442450944 -XX:MarkStackSize=4194304
-XX:MaxGCPauseMillis=50 -XX:MaxHeapSize=6442450944
-XX:MaxNewSize=3865051136 -XX:MinHeapDeltaBytes=2097152
-XX:NumberOfGCLogFiles=10 -XX:+PrintGC -XX:+PrintGCDetails
-XX:+PrintGCTimeStamps -XX:+ReduceSignalUsage
-XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseG1GC
-XX:+UseGCLogFileRotation

The other shows these commandline options:

CommandLine flags: -XX:GCLogFileSize=10485760
-XX:InitialHeapSize=6442450944 -XX:MaxGCPauseMillis=50
-XX:MaxHeapSize=6442450944 -XX:NumberOfGCLogFiles=10 -XX:+PrintGC
-XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+ReduceSignalUsage
-XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseG1GC
-XX:+UseGCLogFileRotation

Aside from one of those sets of options setting the generation sizes
explicitly, there isn't a lot of GC tuning here.  Achieving low pause
times with G1 requires more effort.

I put a fair amount of work into achieving good G1GC results for another
app, and wrote about it on the wiki for the project:

https://wiki.apache.org/solr/ShawnHeisey#GC_Tuning_for_Solr

There are a couple of sets of tuning options that I have used for G1,
and one for CMS that is almost as effective.  Your application may
require different options, but maybe this information will serve as a
starting point.

Thanks,
Shawn