Question regarding G1 option to run parallel Old generation garbage collection?

[Monica Beckwith]

Couple of quick observations and questions -

 1. G1 is officially supported in 7u4. (There are numerous performance
    improvements that I recommend updating to the latest jdk7 update, if
    possible)
 2. What do you mean by old gen collection? Are you talking about MixedGCs?
 3. Instead of setting InitiatingHeapOccupancyPercent to zero, have you
    tried resizing your young generation?
     1. I see the NewRatio, but that fixes the nursery to 640, instead
        have you tried with a lower (than the min default) of nursery
        using the NewSize option?

-Monica



On 10/19/2012 12:13 AM, csewhiz wrote:
> Hello All,
>   Sorry for posting this question in this mailing list. I am unable to 
> find any answer for this. I am trying to tune our application for G1GC 
> as we need very small pauses Below 500msec.
>   But the problem is when we are runing with G1GC (under jdk 6_u37)  
> Old generation of garbage collection only happening when it is 
> reaching the Max GC size I noticed on jdk 6U 37 if max heap size is 
> 1GB then it is close to 1sec 2GB close to 2 sec pauses.
>   Is there any parameter to force the old gc happening regularly.
> I am trying following setting,
> -Xms1280M -Xmx1280M -XX:+UseG1GC -XX:MaxTenuringThreshold=15 
> -XX:SurvivorRatio=8 -XX:NewRatio=1 -XX:GCPauseIntervalMillis=7500 
> -XX:MaxGCPauseMillis=500 -XX:InitiatingHeapOccupancyPercent=0 
> -XX:ParallelGCThreads=7 -XX:ConcGCThreads=7
> If anyone can give insight on how full GC is triggred internals will 
> be of great help.
> PS: I have tried without any option for G1 but not of much help hence 
> .. this one trying to be agressive ? but of not much help.
> Regards,
> Soumit
>

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Oracle <http://www.oracle.com>
Monica Beckwith | Java Performance Engineer
VOIP: +1 512 401 1274 <tel:+1%20512%20401%201274>
Texas
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