Understanding TargetSurvivorRatio

[Denny Kettwig]

Dear all,

Currently I try to understand the TargetSurvivorRatio parameter in detail and after several days of research and tests I  came to no conclusion. So I try to share my thoughts with you.

I tested this parameter in two different ways, setting it to 1 and 99 and then observed the survivor space on the same system actions in both cases.
With the results I got out of my tests I got even more confused than before.

By setting the parameter to 99, I got a very high initial occupancy of the survivor space (about 99% as expected), after 5 minutes it drops down to about 10%. The other scenario, where the
Parameter was set to 1, the occupancy of the survivor space was mostly at %10.

Could you please explain me was this parameter does in detail and how it might affect large server applications to increase the performance by setting the value to 90?

Here are the parameters I used:
set JAVA_OPTS=%JAVA_OPTS% -Xms6g
set JAVA_OPTS=%JAVA_OPTS% -Xmx6g
set JAVA_OPTS=%JAVA_OPTS% -Xmn1g
set JAVA_OPTS=%JAVA_OPTS% -XX:+UseParNewGC
set JAVA_OPTS=%JAVA_OPTS% -XX:+UseConcMarkSweepGC
set JAVA_OPTS=%JAVA_OPTS% -XX:SurvivorRatio=8
set JAVA_OPTS=%JAVA_OPTS% -XX:TargetSurvivorRatio=1 or 99
set JAVA_OPTS=%JAVA_OPTS% -XX:PermSize=256m
set JAVA_OPTS=%JAVA_OPTS% -XX:MaxPermSize=256m
set JAVA_OPTS=%JAVA_OPTS% -XX:+ExplicitGCInvokesConcurrent
set JAVA_OPTS=%JAVA_OPTS% -XX:+CMSClassUnloadingEnabled
set JAVA_OPTS=%JAVA_OPTS% -XX:+UseCompressedOops


Kind Regards

Denny

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.openjdk.java.net/pipermail/hotspot-gc-use/attachments/20130923/177c5bef/attachment.html