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From Michael Dalton <mwdal...@gmail.com>
Subject Re: Tuning question...
Date Wed, 07 Apr 2010 22:36:04 GMT
I believe Escape Analysis has been disabled entirely as of the release of
Java 6u18: http://java.sun.com/javase/6/webnotes/6u18.html . I would hazard
a guess that this is due to some safety/correctness issues (for example,
since 6u16 it's been disabled on Itanium for correctness, and as of 6u18
it's disabled globally). Correct me if I'm wrong on any of this, but is
escape analysis safe at all to turn on in production given that it's totally
disabled now in the most recent Java builds?

Best regards,

Mike

On Wed, Apr 7, 2010 at 1:41 PM, Ryan Rawson <ryanobjc@gmail.com> wrote:

> Hey,
>
> The JVM will auto-tune many of these params.  For example it will set
> the parallel GC threads = # of cpus.  Unless you are having a specific
> problem I wouldn't touch that value.
>
> As for the newSize... the argument is like such.  HBase is constantly
> tenuring tons of data (Block cache is the primary culprit here) and
> left to it's own devices, the JVM would increase the new size until
> the "minor" gc pauses would take something like 800ms or maybe more
> (!!).  So by restricting the new size we are tenuring more data
> frequently, losing the benefit of generational GC, but keeping overall
> GC pause low.  It's a trade off which is forced on us by the way the
> block cache works right now.  A different design of the block cache
> could conceivably help here.
>
> I use this in prod:
> "-XX:+DoEscapeAnalysis -XX:+AggressiveOpts -XX:+UseConcMarkSweepGC
> -XX:NewSize=64m -XX:MaxNewSize=64m
> -XX:CMSInitiatingOccupancyFraction=88 -verbose:gc -XX:+PrintGCDetails
> -XX:+PrintGCTimeStamps"
>
> and things work reasonably well.
>
>
>
>
> On Wed, Apr 7, 2010 at 1:35 PM, Michael Segel <michael_segel@hotmail.com>
> wrote:
> >
> > Hi,
> >
> > I was trying to tune my HBase environment, following the stuff on the
> wiki and I have a question regarding the GC parallel threads setting.
> >
> > Is there a good 'rule of thumb' or formula like 1 thread per core, or
> something?
> > Sorry I'm going from
> memory...-XX:ParallelGCThreads=<number_of_GC_threads>.
> >
> > Also what about the newSize, maxNewSize values? The example says 6M but
> is there any other things to consider?
> >
> > Thx
> >
> > -Mike
> >
> >
> > _________________________________________________________________
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> >
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