G1GC Full GCs

[Todd Lipcon]

On Thu, Jul 8, 2010 at 9:46 AM, Y. S. Ramakrishna <
y.s.ramakrishna at oracle.com> wrote:

>
>
> On 07/07/10 17:32, Todd Lipcon wrote:
> ...
>
>  OK, I can try some tests with cache configured for only 40% heap usage.
>> Should I run these tests with CMS or G1?
>>
>
> I'd first try CMS, and if that works, try G1.


Here's a bzip2 of the full logs from another run I did with the same JDK7
build and CMS:

http://cloudera-todd.s3.amazonaws.com/gc-cms-less-usage.txt.bz2

It took much longer to get to the concurrent mode failure, and the full
pause was shorter (only 6 seconds), but I imagine if I kept it under load
for a long time it would eventually result in the same long GC pause seen
before.

This was configured for 40% heap usage for the main consumers. The histogram
in the logs shows:
   1:       3300462     2374366648  [B
   2:       5317607      170163424  org.apache.hadoop.hbase.KeyValue
   3:       5200626      124815024
 java.util.concurrent.ConcurrentSkipListMap$Node
   4:       2594448       62266752
 java.util.concurrent.ConcurrentSkipListMap$Index
   5:           713       21190544  [J
   6:          3534       10767416  [I
   7:           710       10601456  [[B
   8:         65025        9192480  [C

as the top consumers. This works out to 2654MB, which is under the
configured 3200M 40% mark. (the configuration is really a high-water, after
which it will even reject writes before crossing)

-Todd


-- 
Todd Lipcon
Software Engineer, Cloudera
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.openjdk.java.net/pipermail/hotspot-gc-use/attachments/20100709/2b898137/attachment.html