Heap OOM for no apparent reason?

[Y. Srinivas Ramakrishna]

John was right. I looked at the code and the process
waits for the child to complete and return: the
command is "safepoint-synchronous". May be all
the j* commands are such that they can produce their
results without needing mutator threads to run, because
i also could not find any documented restrictions on the use of
OnOutOfMemoryError.

so, yes, looks like OnOutOfMemoryError will do what you want here,
and my worries were baseless.

thanks John!
-- ramki

On 6/3/2011 8:32 AM, Y. Srinivas Ramakrishna wrote:
> By the way, it would seem that a "safepoint synchronous"
> OnOutOfMemoryError execution would restrict what you could do,
> just in case that caused a deadlock because the target (self)
> might need to be at a non-safepoint to react to that command....
>
> Is there such a documented restriction on what commands can
> be run within OnOutOfMemeoryError (or even a flat caveat emptor)?
>
> -- ramki
>
> On 6/3/2011 8:26 AM, Y. Srinivas Ramakrishna wrote:
>> On 6/3/2011 7:52 AM, Raman Gupta wrote:
>>> On 06/03/2011 03:28 AM, John Coomes wrote:
>>>> Y. Srinivas Ramakrishna (y.s.ramakrishna at oracle.com) wrote:
>>>>> Sorry, sent previous email without addressing all of the issues.
>>>>>
>>>>> On 6/2/2011 6:15 PM, Raman Gupta wrote:
>>>>>> It would be *really* handy if there were a switch like:
>>>>>>
>>>>>> -XX:+StackTraceOnOutOfMemoryError
>>>>>
>>>>> Yes that would be handy, and probably not too difficult.
>>>>> But I wonder also if something like OnOutOfMemoryError or
>>>>> like would already get you enough info to get close to
>>>>> the problem ... (although may be because it's executed in
>>>>> a separate shell, by the time the command executes the
>>>>> process has likely gone well past the point when the problem
>>>>> occurred).
>>>>
>>>> No need to worry, the OnOutOfMemoryError commands are run while the
>>>> JVM is at a safepoint. This worked for me:
>>>>
>>>> java -XX:OnOutOfMemoryError='jstack %p' ...
>>
>> Really, are you sure? I'd assumed you spawn off a separate (i.e. asynchronous)
>> shell process rather than waiting for it to complete while you waited
>> in the safepoint (i.e. synchronous). It could still be that one is
>> "lucky" and the shell happens to complete before the safepoint is
>> exited? Anyway, a good idea to check the code to see if there is
>> a synchronicity guarantee or one relies on plain luck to sometimes
>> get something useful (which itself is not bad, but good to know
>> when it is good fortune vs actual design :-)
>>
>> -- ramki
>>
>>>>
>>>> -John
>>>
>>> Excellent -- will try this later today.
>>>
>>> I did a quick search for places where OOME is caught and swallowed and
>>> found a few places within the JDK (such as direct ByteBuffer
>>> allocation), as well as a couple places in other libraries such as
>>> commons-pool and jgroups, the latter of which is used by Infinispan
>>> (though in some cases, but not all, those are logged before being
>>> swallowed). In short though, I still don't definitively know where the
>>> problem allocation is. So running jstack via OnOutOfMemoryError sounds
>>> like it is just the ticket.
>>>
>>> Cheers,
>>> Raman
>>
>