JVMTI OOM handling when arrays / objects are too large
martinrb at google.com
Mon Jun 29 14:58:26 PDT 2009
Please let me know what mechanics are required to actually integrate this.
Ideally, I'd like to commit both hotspot and jdk repo changes to the
hotspot-runtime forest. If that is not (yet) supported,
I'd like to commit hotspot changes to hotspot-runtime,
and I'll commit the jdk test changes to tl when hotspot changes
trickle down into tl, so that the test doesn't fail when committed.
On Sun, Jun 28, 2009 at 14:42, David Holmes - Sun Microsystems <
David.Holmes at sun.com> wrote:
> I'm not sure what potential refactoring was being referred to given that
> this new fix simply adds a few calls to report_java_out_of_memory() prior to
> throwing the OOME. On that front the actual fix looks fine to me - it adds
> the "OnOOME" handling without messing with JVMTI at all (which means the
> JVMTI mention in the bug synopsis is somewhat misleading.)
Could someone change the synopses of bugs as follows:
6850958: Honor -XX:OnOutOfMemoryError when array size exceeds VM limit
6850957: Honor -XX:OnOutOfMemoryError when array size exceeds VM limit
I've changed URLS to be as follows
> As far as the test goes, yes it should be in hotspot as a jtreg test but
> given you have to check the output of a exec'ed error program I don't know
> how to configure that either. :(
> One issue with the test however: there were four changes made to the VM
> code, but there are only three test cases! Which one is missing?
Hmmmm.... instanceKlass may not be exposed to Java code -
only for arrays of VM-internal objects.
Can a real hotspot engineer confirm?
> And as Alan suggested, as I'm not an official runtime member these days,
> someone from runtime should also "rubber stamp" this.
> Martin Buchholz said the following on 06/28/09 09:58:
>> Alright, I have a new simple version of the hotspot part of the
>> jvmti-oom fix that should make Alan happy.
>> ...Except for the usual problem that the code is screaming
>> for a bit of refactoring, and it's not quite clear what file
>> and function name it should be refactored to. I'll do the
>> easy refactoring if you give me the names to use.
>> Or simply give me thumbs up and I will commit.
>> On Wed, Jun 24, 2009 at 01:15, Alan Bateman <Alan.Bateman at sun.com<mailto:
>> Alan.Bateman at sun.com>> wrote:
>> David Holmes - Sun Microsystems wrote:
>> As I see it there was no consensus reached on whether this
>> change should be made. I have some reservations as previously
>> outlined, but Alan seemed to be of the view that the current
>> situation was deliberately chosen - which implied to me (Alan
>> correct me if I'm wrong) that he opposed the change.
>> It may be that including this case in the OOM onError handling
>> is okay, but that the JVMTI event posting is not. But Alan will
>> need to clarify his position on that.
>> You got it. My view is that we should not post a JVM TI
>> ResourceExhausted event for this case.
>> I think Jeremy's original motive was to have the OnOutOfMemoryError
>> actions run. I don't see a problem changing the code to do that.
>> Yes, the current behavior is deliberate but this option is for
>> troubleshooting and maybe it can help with the (probably rare) cases
>> where this happens.
>> The other point I attempted to make is that if both
>> OnOutOfMemoryError and HeapDumpOnOutOfMemoryError are enabled then
>> we should always generate the heap dump before the
>> OnOutOfMemoryError run. I think we are in agreement that the heap
>> dump is not interesting here but we should still generate it anyway.
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