[9] RFR for JDK-8155004: CrashOnOutOfMemoryError doesn't work for OOM caused by inability to create threads'

[Shafi Ahmad]

Hi,

May I get some comment on this.

Regards,
Shafi

> -----Original Message-----
> From: Shafi Ahmad
> Sent: Wednesday, October 12, 2016 12:42 PM
> To: Mikael Gerdin; hotspot-runtime-dev at openjdk.java.net
> Cc: David Holmes
> Subject: RE: [9] RFR for JDK-8155004: CrashOnOutOfMemoryError doesn't
> work for OOM caused by inability to create threads'
> 
> Hi Mikael,
> 
> Thanks for reviewing it.
> 
> Once VM is initialized, following are two OOME scenarios:
>  1) OOME due to unavailability of java memory [Mainly due to java
> application].
>  2) OOME due to unavailability of native memory.
> 
> Please correct me if I am wrong, for 1) java.lang.OutOfMemoryError is
> correct.
> 
> Consider the following scenarios:
> 1) Let there is java application which uses JNI code and inside JNI code there
> is native memory allocation/free and we hit OOME.
> 2) Let there is java application which uses JNI code and inside JNI code there
> is memory leak error and due to this OOME situation occurs.
> 3) We use jvm option Xms and  -Xmx in such a way that the available native
> memory is very less and VM hit OOME.
> 
> I am not sure above scenario is feasible in JVM or not but if any of the above
> scenario is possible in VM then should we consider it as OOME due java
> application or not?
> I consider case 1) and 2) as OOME due to java application and added code for
> java.lang.OutOfMemoryError inside report_vm_out_of_memory.
> 
> My  assumption of OOME once VM is initialized completely is due to java
> application[directly or indirectly] may not hold true always.
> -XX:+CrashOnOutOfMemoryError is mostly for debugging purpose so I added
> the related code change inside report_vm_out_of_memory.
> Yes, I must not use ' java.lang.OutOfMemoryError'  for such case.
> 
> Please let me know whether I should remove the code change inside
> report_vm_out_of_memory or keep it by adding appropriate reason of
> OutOfMemoryError.
> 
> Regards,
> Shafi
> 
> > -----Original Message-----
> > From: Mikael Gerdin
> > Sent: Monday, October 10, 2016 7:30 PM
> > To: Shafi Ahmad; hotspot-runtime-dev at openjdk.java.net
> > Subject: Re: [9] RFR for JDK-8155004: CrashOnOutOfMemoryError doesn't
> > work for OOM caused by inability to create threads'
> >
> > Hi,
> >
> > On 2016-10-10 09:24, Shafi Ahmad wrote:
> > > Hi All,
> > >
> > > Please review the simple change for the fix of bug '' JDK-8155004:
> > CrashOnOutOfMemoryError doesn't work for OOM caused by inability to
> > create threads'.
> > >
> > > Summary:
> > > In the current implementation there are few scenarios where we are
> > > not
> > obeying the jvm option -XX:+CrashOnOutOfMemoryError.
> > > While I was analysis this issue I found there are two jvm state
> > > where OOM
> > can happen:
> > >  1.  OOM during VM initialization - as per our internal discussion
> > > for this case
> > it is not worth for dumping core file, so this is left as it is.
> > >  2.  OOM once VM is initialized - For this scenario most of the
> > > place code is
> > already added but few place corresponding code changes are missing so
> > this change covers it.
> > >
> > > Webrev link:
> http://cr.openjdk.java.net/~shshahma/8155004/webrev.00/
> >
> >
> > There is a lot of confusion in the VM code with the term "out of
> > memory error".
> > In some places it refers to code throwing a java.lang.OutOfMemoryError
> > and expecting running java code to be able to potentially catch that
> > Error and continue running.
> >
> > In other places, such as callers of report_vm_out_of_memory, the
> > situation is much more dire and the calling thread may not even be a
> > JavaThread and as such cannot "throw" an exception.
> > report_vm_out_of_memory is only invoked through the macro
> > vm_exit_out_of_memory, which of course implies that the condition is
> > fatal and we are about to terminate the JVM process altogether.
> >
> > I think that it's incorrect to call code related to
> > java.lang.OutOfMemoryError in report_vm_out_of_memory since the
> > condition may not even be correlated with Java level application behavior.
> >
> > /Mikael
> >
> > > Jdk9 bug: https://bugs.openjdk.java.net/browse/JDK-8155004
> > >
> > > Testing: jprt and jtreg (on Linux x86_64)
> > >
> > > Regards,
> > > Shafi
> > >