does UseParallelOldGC guarantee a better full gc performance

[Peter B. Kessler]

"swap consumption"?  How much *physical* memory do you have on this box?  (It would be nice if the GC logs included the physical memory available.)  What else is running on the box?

			... peter

the.6th.month at gmail.com wrote:
> Hi, Jon,
> yup,,,I know, but what is weird is the paroldgen doesn't bring about 
> better full gc performance as seen from JMX metrics but bring unexpected 
> swap consumption.
> I am gonna look into my application instead for some inspiration.
> 
> Leon
> 
> On 19 April 2012 00:19, Jon Masamitsu <jon.masamitsu at oracle.com 
> <mailto:jon.masamitsu at oracle.com>> wrote:
> 
>     __
>     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
>     <mailto: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> <mailto:sbordet at intalio.com> wrote:
>>
>>>     Hi,
>>>
>>>     On Wed, Apr 18, 2012 at 10:16, the.6th.month at gmail.com <mailto:the.6th.month at gmail.com>
>>>     <the.6th.month at gmail.com> <mailto: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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