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

[Monica Beckwith]

Hi Kirk -

I see that Charlie has already answered that one. I'll just expand on 
that... Basically *any* value of InitiatingHeapOccupancyPercent is 
checked against the already allocated and current bytes. If the total 
bytes are greater than heap*IHOP/100 (since IHOP is expressed as a 
percent) and if young GC, then we start the concurrent cycle. If not 
then we are doing mixed GC.

-Monica

On 10/19/2012 12:58 PM, Kirk Pepperdine wrote:
> Hi Monica,
>
> Can you comment on what a value of 0 means?
>
> Regards,
> Kirk
>
> On 2012-10-19, at 2:55 PM, Monica Beckwith <monica.beckwith at oracle.com 
> <mailto:monica.beckwith at oracle.com>> wrote:
>
>> 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
>>>
>>
>> -- 
>> <oracle_sig_logo.gif> <http://www.oracle.com/>
>> Monica Beckwith | Java Performance Engineer
>> VOIP: +1 512 401 1274 <tel:+1%20512%20401%201274>
>> Texas
>> <green-for-email-sig_0.gif> <http://www.oracle.com/commitment> Oracle 
>> is committed to developing practices and products that help protect 
>> the environment
>

-- 
Oracle <http://www.oracle.com>
Monica Beckwith | Java Performance Engineer
VOIP: +1 512 401 1274 <tel:+1%20512%20401%201274>
Texas
Green Oracle <http://www.oracle.com/commitment> Oracle is committed to 
developing practices and products that help protect the environment
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