G1gc compaction algorithm

[Martin Makundi]

>  This is a diagnostic parameter, you need to apply with
> -XX:+UnlockDiagnosticVMOptions -XX:+G1PrintRegionLivenessInfo

Thanks, will try that.

 It will first add old regions if the estimated time is under the
> MaxGCPauseMilli.  If the estimated time is higher than  MaxGCPauseMilli, it
> will add the minimum decided by #candidate-regions/MixedGCCountTarget.  If
> you set MixedGCCountTarget too high, the minimum will be too low.  In your
> case, it is 2.
>

Hmm.. what is the logic behind this candidate-regions/MixedGCCountTarget?
Is there no way to tell the gc to estimate the max number of regions it
could maybe achieve in the time available and do that instead of 2?

**
Martin

>  Thanks,
> Jenny
>
> On 7/16/2014 6:46 PM, Martin Makundi wrote:
>
>  2. For most of the time, eden size is 1.4g, survivor 150m, the rest is
>> old gen.  I am not sure how much of the old gen is used for humongous
>> allocations.  But it seems there are some tunings you can try to help mixed
>> gc:
>>   - old regions added to cset is 2-14 for mixed gc.  Most of the time the
>> reason is 'predicted time too high'.  You can try either increase
>> -XX:MaxGCPauseMillis to a higher value, or decrease
>> -XX:G1MixedGCCountTarget (currently it is 80) so that more old regions can
>> be added.
>>
>
>  Does it attempt to do any mixed gc if it cannot do
> all G1MixedGCCountTarget or is the value G1MixedGCCountTarget just an upper
> limit? If it just is an upper limit we could keep it at 80 or higher?
>
>
>
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