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Hi Ramki,<br>
<br>
Thanks for improving the GC logging with these changes.<br>
<br>
What is the reason behind choosing 16M for sparc and 64M for x86
systems as the default value for <span class="new">CMSYoungGenPerWorker
?<br>
<br>
Thanks,<br>
Poonam<br>
<br>
</span>On 3/15/2011 7:37 AM, Y. Srinivas Ramakrishna wrote:
<blockquote cite="mid:4D7EC9CC.4000902@oracle.com" type="cite">(bug)
6627787: CMS: JVM refuses to start up with -Xms16m -Xmx16m
<br>
(RFE) 6896099: Integrate CMS heap ergo with default heap sizing ergo
<br>
(bug) 7000125: CMS: Anti-monotone young gen sizing with respect to
maximum whole heap size specification
<br>
<br>
Problem: CMS heap sizing does not make use of server/client heap sizing
<br>
ergo, mainly because it wants to keep maximum gc pauses somewhat
<br>
under control rather than necessarily sizing for throughput.
<br>
There have been many changes and small tweaks over the years
<br>
in this code and it has collected a lot of unnecessary settings
<br>
which also conflict with the sizing decisions being made
<br>
elsewhere in the heap sizing/policy subsystem, resulting,
<br>
for example, in the two bugs in the list of CR's above.
<br>
<br>
Solution: Allow CMS to make use of server/client heap sizing
<br>
ergonomics, just like all the other collectors, while keeping the
<br>
young generation small enough so as to keep pause times
<br>
reasonable. One of these required a CPU-specific default.
<br>
Jettison old settings and flags specific to use in JDK 6
<br>
to preserve JDK 5 like CMS settings, which are now considered
<br>
quite obsolete.
<br>
<br>
Since the fixes for the two defects and the one RFE were
<br>
entangled, it made sense to fix them all in one changeset.
<br>
<br>
Testing: internal reference workloads to assess the changes
<br>
from current settings, and to ensure that gc pauses are
<br>
still "reasonable" with the newer default settings.
<br>
The command-lines in the two bugs to verify that the
<br>
sizing anomalies are no longer present.
<br>
<br>
Webrev:
<a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~ysr/6627787_6896099_7000125/webrev.01/">http://cr.openjdk.java.net/~ysr/6627787_6896099_7000125/webrev.01/</a>
<br>
<br>
This contains changes following one internal review (thanks Bengt
Rutisson!),
<br>
but if anyone else has further feedback, please let me know.
<br>
<br>
thanks!
<br>
-- ramki
<br>
</blockquote>
<br>
<div class="moz-signature">-- <br>
Best regards, Poonam
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