does UseParallelOldGC guarantee a better full gc performance

[Simone Bordet]

Hi,

On Wed, Apr 18, 2012 at 10:16, the.6th.month at gmail.com
<the.6th.month at gmail.com> wrote:
> hi all:
> I'm currently using jdk 6u26. I just enabled UseParallelOldGC, expecting
> that would enhance the full gc efficiency and decrease the mark-sweep time
> by using multiple-core. The JAVA_OPTS is as below:
> -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintTenuringDistribution
> -Xloggc:gc.log-server -Xms4000m -Xmx4000m -Xss256k -Xmn256m
> -XX:PermSize=256m -XX:+UseParallelOldGC  -server
> -Dorg.apache.jasper.compiler.Parser.STRICT_QUOTE_ESCAPING=false
> as shown in jinfo output, the settings have taken effect, and the
> ParallelGCThreads is 4 since the jvm is running on a four-core server.
> But what's strange is that the mark-sweep time remains almost unchanged (at
> around 6-8 seconds), do I miss something here? Does anyone have the same
> experience or any idea about the reason behind?
> Thanks very much for help

The young generation is fairly small for a 4GiB heap.

Can we see the lines you mention from the logs ?

Simon
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