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thank you both for the fast replies,<br>
<br>
I will try all suggestions tomorrow. The App is already in production
this means it is only possible to reboot at night. I will also add a
full gc log and try to update to latest JDK 5 update release.<br>
<br>
thanks for the support, I already learned a lot through your answers<br>
<br>
-michael<br>
<br>
<br>
Y Srinivas Ramakrishna schrieb:
<blockquote cite="mid:f86ec5291a39.4948ed9e@sun.com" type="cite">
<pre wrap="">oh and, as Jon suggested before, it might be a good
idea to tack on -XX:+DisableExplicitGC to ensure that
it's not RMI or other modules calling system.gc() here,
unbeknownst to you. (If nothing else but to get closer to the
root cause of the puzzling full gc's.)
-- ramki
----- Original Message -----
From: Y Srinivas Ramakrishna <a class="moz-txt-link-rfc2396E" href="mailto:Y.S.Ramakrishna@Sun.COM"><Y.S.Ramakrishna@Sun.COM></a>
Date: Wednesday, December 17, 2008 12:12 pm
Subject: Re: CMS does not want to run concurrently
To: Jon Masamitsu <a class="moz-txt-link-rfc2396E" href="mailto:Jon.Masamitsu@Sun.COM"><Jon.Masamitsu@Sun.COM></a>
Cc: <a class="moz-txt-link-abbreviated" href="mailto:hotspot-gc-use@openjdk.java.net">hotspot-gc-use@openjdk.java.net</a>
</pre>
<blockquote type="cite">
<pre wrap="">Just a quick remark related to:-
...
</pre>
<blockquote type="cite">
<pre wrap="">Here in the CMS gen (old generation) it is only 325384K full (out of
a total of 659140K) when the collection starts. Actually, you might
have a severely fragmented heap. In that case Full GC's would happen
and using the survivor spaces would help.
</pre>
</blockquote>
<pre wrap="">When you have a fragmented heap that causes a full collection
the gc log message (in 5u8) would look a bit different as a
scavenge is first attempted, but fails because of a fragmented
heap, and then bails to a full collection. Because I do not see
that abortive scavenge attempt logged here, I suspect this may not
be a fragmentation-induced full gc, but perhaps something
else. Nonetheless, Jon's suggestion of using survivor spaces
to stem the tenuring of very young objects would be a good
thing to reduce fragmentation and other stresses on CMS.
-- ramki
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