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<div class="moz-cite-prefix">Markus,<br>
<br>
You need to include all three mailing list in the same mail, or
else the mail threads will diverge.<br>
<br>
thanks,<br>
StefanK<br>
<br>
On 2014-06-23 17:26, Markus Grönlund wrote:<br>
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<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">Sending
this to the Hotspot-GC-dev group as well.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US">/Markus<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D" lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US"> Markus Grönlund <br>
<b>Sent:</b> den 23 juni 2014 17:03<br>
<b>To:</b> hotspot-runtime-dev; serviceability-dev<br>
<b>Subject:</b> RFR(S): 8047812: Ensure
ClassLoaderDataGraph::classes_unloading_do only delivers
klasses from CLDs with non-reclaimed class loader oops<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US">Greetings,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Kindly asking for
reviews for the following change:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Bug: <a
moz-do-not-send="true"
href="https://bugs.openjdk.java.net/browse/JDK-8047812">https://bugs.openjdk.java.net/browse/JDK-8047812</a><o:p></o:p></span></p>
<p class="MsoNormal">Webrev: <a moz-do-not-send="true"
href="http://cr.openjdk.java.net/%7Emgronlun/8047812/webrev01">http://cr.openjdk.java.net/~mgronlun/8047812/webrev01</a>
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US">Description:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The "8038212:
Method::is_valid_method() check has performance regression <br>
impact for stackwalking" - changeset introduced a change
in how the ClassLoaderDataGraph::_unloading list of
ClassLoaderData's is purged. <br>
<br>
This change to the purging of the CLD’s work the same as
before for most GC's, but when using CMS GC,
SystemDictionary::do_unloading() is called twice with no
explicit purge call in between. On the second call
(post-sweep), we can now get stale class loader oops
delivered as part of the Klass closure callbacks from the
_unloading list. Again, this is because there is no explicit
purge call in between these two entries to
SystemDictionary::do_unloading() - and being CMS and
concurrent, it is very hard to accommodate a timely and
proper purge call here.<br>
<br>
The first do_unloading call comes after CMS concurrent
marking, and the second comes from a Full GC triggered while
sweeping the CMS heap. <br>
<br>
This fix ensures the unloading purge mechanism to work
correctly also for the CMS collector, in that only CLDs with
non-reclaimed class loader oops will deliver klasses from
the _unloading list. In addition, this will ensure a single
"logical" pass is achieved when iterating the unloading list
in-between purges (avoiding the processing of the same data
twice). <br>
<br>
This fix is precipitated by nightly testing failures with
CMS after the introduction of 8038212:
Method::is_valid_method() check has performance regression <br>
impact for stackwalking" - for example
"nsk/sysdict/vm/stress/jck12a//sysdictj12a008" which is
crashing because of following up stale klass loader oop's
from the ClassLoaderDataGraph::_unloading list.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thanks<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Markus<o:p></o:p></span></p>
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