Review Request: UseNUMAInterleaving

[Igor Veresov]

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

>
> 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
>>>
>>>
>>>
>>>
>
>