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Hi David,<br>
<br>
On 11/11/2011 11:48 AM, David Holmes wrote:
<blockquote cite="mid:4EBCBE4D.8020002@oracle.com" type="cite">Hi
Poonam,
<br>
<br>
I've cc'ed GC-dev as this is more their area. It seems very
wasteful to potentially ensure_parsability and also do a full GC.
And the check for the active GC_Locker is somewhat arbitrary as it
could change the instant you've queried it.
<br>
<br>
</blockquote>
Thanks for adding GC-dev.<br>
<br>
<blockquote cite="mid:4EBCBE4D.8020002@oracle.com" type="cite">It
seems to me that a more complete solution here would enable
collect_as_vm_thread to indicate whether or not GC occurred. Which
in turn requires that do_full_collection report that info - a RFE
that is already noted in the G1 code at least:
<br>
<br>
void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs)
{
<br>
// do_collection() will return whether it succeeded in
performing
<br>
// the GC. Currently, there is no facility on the
<br>
// do_full_collection() API to notify the caller than the
collection
<br>
// did not succeed (e.g., because it was locked out by the GC
<br>
// locker). So, right now, we'll ignore the return value.
<br>
bool dummy = do_collection(true, /* explicit_gc
*/
<br>
clear_all_soft_refs,
<br>
0 /* word_size
*/);
<br>
}
<br>
<br>
</blockquote>
Yes, that would be the ideal solution.<br>
<br>
What is the time frame of having this RFE implemented for other
collectors? This bug was discovered during the FMW stress testing
and needs to fixed as soon as we can. <br>
<br>
The solution I proposed is being used by other VM operations as well
e.g. VM_GC_HeapInspection and was somehow missed for VM_HeapDumper..
So, I guess until we have the RFE implemented that allows us to have
the result whether a GC succeeded or not, this could be a short
term solution.<br>
<br>
<br>
Thanks,<br>
Poonam<br>
<br>
<br>
<blockquote cite="mid:4EBCBE4D.8020002@oracle.com" type="cite">David
<br>
-----
<br>
<br>
On 11/11/2011 3:20 PM, <a class="moz-txt-link-abbreviated" href="mailto:poonam.bajaj@oracle.com">poonam.bajaj@oracle.com</a> wrote:
<br>
<blockquote type="cite">Hi,
<br>
<br>
Can I get a couple of reviews for this change:
<br>
<br>
CR 7110428: Crash during HeapDump operation
<br>
<a class="moz-txt-link-freetext" href="http://monaco.sfbay.sun.com/detail.jsf?cr=7110428">http://monaco.sfbay.sun.com/detail.jsf?cr=7110428</a>
<br>
<br>
The crash happens when VM thread traverses the heap during
heapdump
<br>
operation and it finds the heap in non-parseable state. The heap
can be
<br>
left in non-parseable state if due to some reason GC is skipped
and we
<br>
didn't call ensure_parsability() either before dumping the heap.
The
<br>
solution is to always call ensure_parsability() In
<br>
VM_HeapDumper::doit(), whether or not a GC is requested before
the heap
<br>
dumping.
<br>
<br>
<a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~poonam/7110428/webrev.00/">http://cr.openjdk.java.net/~poonam/7110428/webrev.00/</a>
<br>
<br>
<br>
Thanks,
<br>
Poonam
<br>
<br>
<br>
</blockquote>
</blockquote>
<br>
<div class="moz-signature">-- <br>
Best regards, Poonam
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