Review Request: UseNUMAInterleaving
dmdabbs at gmail.com
Mon May 16 13:04:16 PDT 2011
> -----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.
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?
> > Could this flag help Linux systems with kernel< 2.6.19, or is that
> > 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
> > 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
> > provide automatic memory placement optimisations for Java
> > Typically, every processor in the system has a local memory that
> > 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
> > 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:
> > evaluated against the SPEC JBB 2005 benchmark on an 8 chip Opteron
> > NUMA-aware systems gave about a 30% (for 32-bit) to 40% (for 64-bit)
> > increase in performance.
> > Thanks,
> > David
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