Review Request: UseNUMAInterleaving

[David Dabbs]

> -----Original Message-----
> From: Igor Veresov [mailto:igor.veresov at oracle.com]
> Sent: Monday, May 16, 2011 4:28 PM
> To: David Dabbs
> Cc: 'Deneau, Tom'; hotspot-compiler-dev at openjdk.java.net
> Subject: Re: Review Request: UseNUMAInterleaving
> 
> On 5/16/11 1:04 PM, David Dabbs wrote:
> >
> >
> >> -----Original Message-----
> >> From: Igor Veresov
> >> Sent: Monday, May 16, 2011 2:54 PM
> >> To: David Dabbs
> >> Subject: Re: Review Request: UseNUMAInterleaving
> >>
> >> On 5/16/11 11:21 AM, David Dabbs wrote:
> >>
> >> The 2.6.19 requirement is there because we need the sched_getcpu()
> >> syscall to determine on which CPU we're running.
> >>
> >> I guess it won't be hard to extend UseNUMAInterleaving to work on
> other
> >> OSes, including old Linuxes. You can, however, achieve the same
> effect
> >> by running the VM with "numactl -i all java<your-options>" or by
> >> turning interleaving on in BIOS in hardware.
> >>
> >> igor
> >>
> >
> > Thank you for the info, Igor. So these two options you provided
> should
> > work for an "old Linux" (2.6.18, glibc-2.5-49.el5_5.7)? Are they
> equivalent?
> >
> 
> I don't actually recall what interleaving granularity will the hardware
> option provide. It could be less than a page (which would be the
> minimum
> granularity of any software method). Tom probably knows more about
> that.
> 
> Also, the numactl method won't work if you're using large pages.
> 
> igor
> 


I was afraid LargePages would be a deal-killer. We use a 2M page size. Oh
well.
Thank you.

David


> >
> > Thank you,
> >
> > David
> >
> >
> >
> >>>
> >>>
> >>> Could this flag help Linux systems with kernel<   2.6.19, or is
> that
> >> the
> >>> minimum kernel needed for any JVM NUMA support?
> >>> Unfortunately, we run CentOS 5.5 (2.6.18)
> >>>
> >>> Linux node01.int 2.6.18-194.17.4.el5 #1 SMP Mon Oct 25 15:50:53 EDT
> >> 2010
> >>> x86_64 x86_64 x86_64 GNU/Linux
> >>>
> >>> and so -XX:+UseNUMA does not activate (at least not according to
> >>> PrintFlagsFinal).
> >>>
> >>>>  From http://www.infoq.com/news/2010/01/java6u18
> >>> In the Java HotSpot VM, the NUMA-aware allocator has been
> implemented
> >> to
> >>> provide automatic memory placement optimisations for Java
> >> applications.
> >>> Typically, every processor in the system has a local memory that
> >> provides
> >>> low access latency and high bandwidth, and remote memory that is
> >>> considerably slower to access. The NUMA-aware allocator is
> >> implemented for
> >>> Solaris (>= 9u2) and Linux (kernel>= 2.6.19, glibc>= 2.6.1)
> operating
> >>> systems, and can be turned on for the Parallel Scavenger garbage
> >> collector
> >>> with the -XX:+UseNUMA flag. Parallel Scavenger remains the default
> >> for a
> >>> server-class machine and can also be turned on explicitly by
> >> specifying the
> >>> -XX:+UseParallelGC option. The impact of the change is significant:
> >> When
> >>> evaluated against the SPEC JBB 2005 benchmark on an 8 chip Opteron
> >> machine,
> >>> NUMA-aware systems gave about a 30% (for 32-bit) to 40% (for 64-
> bit)
> >>> increase in performance.
> >>>
> >>>
> >>>
> >>> Thanks,
> >>>
> >>> David
> >>>
> >>>
> >>>
> >>>
> >
> >