ResourceExhausted JVMTI event and -XX:*OnOutOfMemoryError

[David Holmes]

Hi Yasumasa,

On 23/07/2019 5:24 pm, Yasumasa Suenaga wrote:
> Hi all,
> 
> I tried to use JVMTI agent which hooks ResourceExhausted event and 
> -XX:ExitOnOutOfMemoryError together.
> The process was exited when OutOfMemoryError was occurred, but 
> ResourceExhausted event was not fired.
> 
> I checked HotSpot implementation, -XX:*OutOfMemoryError is processed 
> before JVMTI event processing.
> 
> http://hg.openjdk.java.net/jdk/jdk/file/d999a1a11485/src/hotspot/share/gc/shared/memAllocator.cpp#l125 
> 
> 
> IMHO ResourceExhausted should be called before -XX:*OutOfMemoryError.
> If it is a bug, I will file it to JBS and fix it.

I don't think it is a bug. First, there's no specification for how these 
two things interact - -XX:*OnOutOfMemoryError is just a VM specific 
debugging/diagnostic hook. Second, if we're out of memory then we don't 
want to be doing other things which may need to also acquire memory. 
Third, no matter which way you code this someone may in some case want 
it the other way - and it's not worth coding to allow such flexibility IMO.

Just my $2. :)

Cheers,
David

> 
> Thanks,
> 
> Yasumasa