does UseParallelOldGC guarantee a better full gc performance

[Jon Masamitsu]

Leon,

In this log you see as part of an entry "PSOldGen:" which says you're
using the serial mark sweep.  I see in your later posts that "ParOldGen:"
appears in your log and that is the parallel mark sweep collector.

Jon

On 4/18/2012 1:58 AM, the.6th.month at gmail.com wrote:
> Hi, Simon:
>
> this is the full gc log for your concern.
> 2012-04-18T16:47:24.824+0800: 988.392: [GC
> Desired survivor size 14876672 bytes, new threshold 1 (max 15)
>   [PSYoungGen: 236288K->8126K(247616K)] 4054802K->3830711K(4081472K),
> 0.0512250 secs] [Times: user=0.15 sys=0.00, real=0.05 secs]
>
> 2012-04-18T16:47:24.875+0800: 988.443: [Full GC [PSYoungGen:
> 8126K->0K(247616K)] [PSOldGen: 3822585K->1751429K(3833856K)]
> 3830711K->1751429K(4081472K) [PSPermGen: 81721K->81721K(262144K)],
> 6.6108630 secs] [Times: user=6.62 sys=0.00, real=6.61 secs]
>
> the full gc time is almost unchanged since I enabled paralleloldgc.
>
> Do you have any recommendation for an appropriate young gen size?
>
> Thanks
>
> All the best,
> Leon
>
>
> On 18 April 2012 16:24, Simone Bordet<sbordet at intalio.com>  wrote:
>
>> 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
>> --
>> http://cometd.org
>> http://intalio.com
>> http://bordet.blogspot.com
>> ----
>> Finally, no matter how good the architecture and design are,
>> to deliver bug-free software with optimal performance and reliability,
>> the implementation technique must be flawless.   Victoria Livschitz
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>
>
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