linux-kernel - Re: 3.1-rc2: CONFIG

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Date:	Thu, 18 Aug 2011 07:59:26 -0400 (EDT)
From:	Justin Piszcz <jpiszcz@...idpixels.com>
To:	Américo Wang <xiyou.wangcong@...il.com>
cc:	linux-kernel@...r.kernel.org, linux-numa@...r.kernel.org,
	Alan Piszcz <ap@...arrain.com>
Subject: Re: 3.1-rc2: CONFIG_NUMA Question


On Thu, 18 Aug 2011, Américo Wang wrote:

> On Thu, Aug 18, 2011 at 6:51 PM, Justin Piszcz <jpiszcz@...idpixels.com> wrote:
>> Hi,
>>
>> I have a SuperMicro X8DTH-6F motherboard with 2 cpus it has NUMA options in
>> the BIOS; what parameters/should I be using for the NUMA options in the
>> kernel?
>>
>>  | |    [*] Numa Memory Allocation and Scheduler Support                 | |
>>  | |    [ ] Old style AMD Opteron NUMA detection                         | |
>>  | |    [*] ACPI NUMA detection                                          | |
>>  | |    [ ] NUMA emulation                                               | |
>>  | |    (6) Maximum NUMA Nodes (as a power of 2)                         | |
>>
>
> That is Intel processor, right? If so, the things you selected here are enough,
Hi, yes-- two Intel Xeon E5645s.

> the rest two is not what you need.
Ok.

>
>> Specifically, the maximum number of NUMA nodes?  Will this help to increase
>> performance of large memory allocations/is there any downside
>> to enabling this feature?
>
> The max of NUMA nodes is specified by CONFIG_NODES_SHIFT,
> in your case, it is 6, which means it supports up to 2^6 nodes.
Ok, is there any overhead having more than is needed?

>
> If your hardware supports NUMA, yes, that certainly help to increase
> the performance.
Nice, thanks.

Justin.