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Jon,<br>
<br>
I noticed that you are using the incremental mode of<br>
CMS. May I ask why you chose to turn that on?<br>
<br>
Jon<br>
<br>
On 10/31/2011 7:43 PM, Jon Masamitsu wrote:
<blockquote cite="mid:4EAF5CCD.5030004@oracle.com" type="cite">Jon,
<br>
<br>
I haven't looked at the longer log but in general I've found the
<br>
information in the GC logs inadequate to figure out if the
<br>
problem is fragmentation. But more important, there has
<br>
been some good work in recent versions of hotspot so that
<br>
we're more successful at combating fragmentation. Try
<br>
the latest release and see if it helps (u26 should be good
<br>
enough).
<br>
<br>
Jon
<br>
<br>
On 10/31/11 06:06, Jon Bright wrote:
<br>
<blockquote type="cite">Hi,
<br>
<br>
We have an application running with a 6GB heap (complete
parameters below). Mostly it has a fairly low turnover of
memory use, but on occasion, it will come under some pressure as
it reloads a large in-memory data set from a database.
<br>
<br>
Sometimes in this situation, we'll see a concurrent mode
failure. Here's one failure:
<br>
<br>
20021.464: [GC 20021.465: [ParNew: 13093K->3939K(76672K),
0.0569240 secs]20021.522: [CMS20023.747: [CMS-concurrent-mark:
11.403/29.029 secs] [Times: user=41.11 sys=1.03, real=29.03
secs]
<br>
(concurrent mode failure): 3873922K->2801744K(6206272K),
30.7900180 secs] 3886215K->2801744K(6282944K), [CMS Perm :
142884K->142834K(524288K)] icms_dc=33 , 30.8473830 secs]
[Times: user=30.26 sys=0.71, real=30.85 secs]
<br>
Total time for which application threads were stopped:
30.8484460 seconds
<br>
<br>
(I've attached a lengthier log including the previous and
subsequent CMS collection.)
<br>
<br>
Am I correct in thinking that this failure can basically only be
caused by fragmentation? Both young and old seem to have plenty
of space. There doesn't seem to be any sign that the tenured
generation would run out of space before CMS completes.
Fragmentation is the only remaining cause that occurs to me.
<br>
<br>
We're running with 1.6.0_11, although this will be upgraded to
1.6.0_26 tomorrow. I realise our current version is ancient -
I'm not really looking for help on the problem itself, just for
advice on whether the log line above indicates fragmentation.
<br>
<br>
Thanks
<br>
<br>
Jon Bright
<br>
<br>
<br>
<br>
The parameters we have set are:
<br>
<br>
-server
<br>
-Xmx6144M
<br>
-Xms6144M
<br>
-XX:MaxPermSize=512m
<br>
-XX:PermSize=512m
<br>
-XX:+UseConcMarkSweepGC
<br>
-XX:+CMSIncrementalMode
<br>
-XX:+CMSIncrementalPacing
<br>
-XX:SoftRefLRUPolicyMSPerMB=3
<br>
-XX:CMSIncrementalSafetyFactor=30
<br>
-XX:+PrintGCDetails
<br>
-XX:+PrintGCApplicationStoppedTime
<br>
-XX:+PrintGCApplicationConcurrentTime
<br>
-XX:+PrintGCTimeStamps
<br>
-Xloggc:/home/tbmx/log/gc_`date +%Y%m%d%H%M`.log
<br>
<br>
<br>
<br>
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<br>
</blockquote>
<br>
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