GC Parameters for low-latency

[Jon Masamitsu]

Do not use UseAdaptiveSizePolicy with CMS.   The implementation for CMS
is incomplete. Never use  UseAdaptiveGCBoundary.  There are known problems
with that option.

UseAdaptiveSizePolicy should only be used with UseParallelGC and
UseParallelOldGC.


On 11/16/2011 7:02 AM, Ralf Helbing wrote:
> dear mailing list,
>
> we try to achieve low latencies despite using a huge heap (10G) and many
> logical cores (64).
> VM is 1.7u1. Ideally, we would let GC ergonomics decide what is best,
> giving only a low pause time goal (50ms).
>
> -Xss2m
> -Xmx10000M
> -XX:PermSize=256m
> -XX:+UseAdaptiveGCBoundary
> -XX:+UseAdaptiveSizePolicy
> -XX:+UseConcMarkSweepGC
> -XX:MaxGCPauseMillis=100
> -XX:ParallelGCThreads=12
>
> -XX:+BindGCTaskThreadsToCPUs
> -XX:+UseGCTaskAffinity
>
> -XX:+UseCompressedOops
> -XX:+DoEscapeAnalysis
>
> Whenever we use adaptive sizes, the VM will crash in GenCollect*, as
> soon as some serious allocations start. I already filed a bug for this
> (7112413).
>
> Assuming a small newsize helps maintaining a low pause time goal, I can
> set the newsize, too. Say I set it to 100MB, it will increase later
> anyway, again yielding frequent pause times in over 1s by the time the
> newsize is around 1G.
>
> What am I doing wrong here?
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