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From the sound of what Thomas is describing, this might be one of
those apps that's making heavy use of SoftReferences. Output from
-XX:+PrintReferenceGC as Bengt suggested will show if that's the
case.<br>
<br>
If we see a large number of SoftReferences being processed per GC,
we may get further help with tuning the SoftReference reclamation
policy, (-XX:SoftRefLRUPolicyMSPerMB).<br>
<br>
charlie<br>
<br>
<div class="moz-cite-prefix">On 05/16/2014 07:32 AM, Bengt Rutisson
wrote:<br>
</div>
<blockquote
cite="mid:BFB2E06B-572C-422F-9C57-08283290376A@oracle.com"
type="cite">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div><br>
</div>
<div>Hi Thomas,</div>
<div><br>
</div>
<div><br>
16 maj 2014 kl. 14:01 skrev Thomas Viessmann <<a
moz-do-not-send="true"
href="mailto:thomas.viessmann@oracle.com">thomas.viessmann@oracle.com</a>>:<br>
<br>
</div>
<blockquote type="cite">
<div>
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http-equiv="Content-Type">
Hi Bengt,<br>
<br>
<br>
Thanks for confirming. ParallelOld had stop pauses in the
range of 20 to 30 seconds.<br>
CMS was a disaster due to extreme fragmentation and high
promotion rate even with<br>
huge eden and survivors.</div>
</blockquote>
<div><br>
</div>
<div>Ok, so even with the long remark pauses G1 is performing
better than the other GCs?</div>
<div><br>
</div>
<br>
<blockquote type="cite">
<div> There are definitely lots of references. I can find out<br>
details.<br>
</div>
</blockquote>
<div><br>
</div>
<div>Thanks, it would be interesting to get this data. </div>
<div><br>
</div>
<div>Thanks,</div>
<div>Bengt</div>
<br>
<blockquote type="cite">
<div> <br>
Thanks and Regards<br>
<br>
Thomas <br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 05/16/14 13:53, Bengt Rutisson
wrote:<br>
</div>
<blockquote cite="mid:5375FC23.5040004@oracle.com" type="cite">
<meta content="text/html; charset=UTF-8"
http-equiv="Content-Type">
<br>
Hi again Thomas,<br>
<br>
<br>
<div class="moz-cite-prefix">On 2014-05-16 13:34, Thomas
Viessmann wrote:<br>
</div>
<blockquote cite="mid:5375F7AB.1070908@oracle.com"
type="cite">
<meta content="text/html; charset=UTF-8"
http-equiv="Content-Type">
Hi Bengt,<br>
<br>
Sure, the application has lots of objects and references.<br>
Downsizing the application has been tried The heap size of
24 g is <br>
already at minimum. A smaller heap gave OutOfmemory
really quick.<br>
My question was more whether the remark phases could be
optimized<br>
further. I assume this is not the case and we have reached
the limitations <br>
of G1, right? <br>
</blockquote>
<br>
<br>
How many reference objects does the application use? Can you
run it with -XX:+PrintReferenceGC to see how many there are?<br>
<br>
If there are a lot of them I don't think there is much more
that can be done for the remark phase. But if there are not
that many I guess it means that the remark phase is
inefficient.<br>
<br>
Have you tried any of the other GCs? How do they behave with
this application?<br>
<br>
Thanks,<br>
Bengt<br>
<br>
<br>
<blockquote cite="mid:5375F7AB.1070908@oracle.com"
type="cite"> <br>
Thanks and Regards<br>
<br>
Thomas <br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 05/16/14 13:18, Bengt
Rutisson wrote:<br>
</div>
<blockquote cite="mid:5375F3F5.7030808@oracle.com"
type="cite">
<meta content="text/html; charset=UTF-8"
http-equiv="Content-Type">
<br>
Hi Thomas,<br>
<br>
<div class="moz-cite-prefix">On 2014-05-16 13:10, Thomas
Viessmann wrote:<br>
</div>
<blockquote cite="mid:5375F22E.90003@oracle.com"
type="cite">
<meta content="text/html; charset=UTF-8"
http-equiv="Content-Type">
<tt>Hi Bengt,</tt><tt><br>
</tt><tt><br>
</tt><tt>Well, that's already done and it did improve
things</tt>.<br>
<pre>argv[21]: -XX:+ParallelRefProcEnabled
argv[22]: -XX:ParallelGCThreads=48</pre>
</blockquote>
<br>
Sorry, I missed that.<br>
<br>
<blockquote cite="mid:5375F22E.90003@oracle.com"
type="cite">
<pre>before -XX:+ParallelRefProcEnabled was set the stop times were in the range of 20 to 60 seconds.</pre>
</blockquote>
<br>
OK. Glad it helped some. :)<br>
<br>
<blockquote cite="mid:5375F22E.90003@oracle.com"
type="cite">
<pre>The application is a Cacao by Oracle. So they cannot change it.</pre>
</blockquote>
<br>
Is there some way of reducing the amount of reference
objects that Cacao uses? Does it have cache sizes or
similar that can be tuned. With a JFR recording we might
be able to figure out where the reference objects come
from.<br>
<br>
Thanks,<br>
Bengt<br>
<br>
<blockquote cite="mid:5375F22E.90003@oracle.com"
type="cite">
<pre>Thanks and Regards
Thomas
</pre>
<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 05/16/14 12:58, Bengt
Rutisson wrote:<br>
</div>
<blockquote cite="mid:5375EF5A.3050707@oracle.com"
type="cite"> <br>
Hi Thomas, <br>
<br>
It looks like the application is using a lot of
Reference objects. The time spent in remark is
dominated by reference processing. See the attached
graph generated from the log file you sent. <br>
<br>
You can try to see if adding
-XX:+ParallelRefProcEnabled improves the situation.
<br>
<br>
If the customer is interested in updating their
application they might want to see if they can
reduce the number of java.lang.ref.Reference objects
they use. <br>
<br>
Hths, <br>
Bengt <br>
<br>
<br>
On 2014-05-16 10:26, Thomas Viessmann wrote: <br>
<blockquote type="cite">Hi, <br>
<br>
<br>
I've been tuning a Java 7u51, Solaris 10, T4
system with 24G heap. <br>
My customer is not very happy with the remark
pauses of up to 2 seconds. <br>
-XX:ParallelGCThreads=48 turned out to be the
optimum. Here is the log file <br>
which contains the java args at the top: <br>
<br>
<a moz-do-not-send="true"
class="moz-txt-link-freetext"
href="http://aubing.de.oracle.com/gclog/gc_log_03052014.log">http://aubing.de.oracle.com/gclog/gc_log_03052014.log</a>
<br>
<br>
Any idea to drive the remark stop times further
down? <br>
<br>
<br>
Thanks and Regards <br>
<br>
Thomas <br>
</blockquote>
<br>
</blockquote>
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