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From Shawn Heisey <s...@elyograg.org>
Subject Re: Low pause GC for java 1.6
Date Sun, 01 Jul 2012 16:20:45 GMT
On 6/30/2012 7:48 PM, Bill Bell wrote:
> Nothing?
>
> Bill Bell
> Sent from mobile
>
>
> On Jun 29, 2012, at 9:09 PM, Bill Bell <billnbell@gmail.com> wrote:
>
>> We are getting large Solr pauses on Java garbage collection in 1.6 Java.
>>
>> We have tried CMS. But we still have. 4 second wait on GC.
>>
>> What works well for Solr when using 16 GB of RAM?
>>
>> I have read lots of articles and now just looking for practical advise and examples.

Bill, this is what I am using to minimize GC impact on Solr:

-Xms4096M
-Xmx8192M
-XX:NewRatio=1
-XX:+UseParNewGC
-XX:+UseConcMarkSweepGC
-XX:+CMSParallelRemarkEnabled

The key seems to be having a large chunk of memory for the new 
generation (eden), so that it's not forced to heavily use the old 
generation.  With a NewRatio of 1, half the memory gets used for the old 
generation, the other half is divided up among eden and survivor spaces, 
with eden getting most of it.  I don't know what the default is, but 
whatever it is resulted in a pretty small eden space, and I was doing a 
lot of full GCs.

As of this moment, Solr (3.5.0) and Jetty are using a little less than 
5GB of RAM.  At an uptime of 53190.8 seconds (14 hours), there were 229 
young garbage collections that took a total of 30.522 seconds.  There 
were 14 full garbage collections that took a total of 9.351 seconds.  
These numbers come from jstat with a 5000 millisecond interval.

jstat -gc -t -h12 <pid> 5000

I don't think you can specify a NewRatio below 1, so if you end up 
needing more eden space than that can give you, you can set an explicit 
NewSize instead.

Thanks,
Shawn


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