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SubjectRe: [PATCH] x86-32: Allocate irq stacks seperate from percpu area
Hello,

On 10/27/2010 03:33 PM, Eric Dumazet wrote:
> Le mercredi 27 octobre 2010 à 11:57 +0200, Peter Zijlstra a écrit :
>> On Wed, 2010-10-27 at 08:07 +0200, Eric Dumazet wrote:
>>>> - irqctx = &per_cpu(hardirq_stack, cpu);
>>>> + irqctx = (union irq_ctx *)__get_free_pages(THREAD_FLAGS, THREAD_ORDER);
>>>
>>> Hmm, then we lose NUMA affinity for stacks.
>>
>> I guess we could use:
>>
>> alloc_pages_node(cpu_to_node(cpu), THREAD_FLAGS, THREAD_ORDER);
>>
>>
>
> Anyway, I just discovered per_cpu data on my machine (NUMA capable) all
> sit on a single node, if 32bit kernel used.
>
> # cat /proc/buddyinfo
> Node 0, zone DMA 0 1 0 1 2 1 1 0 1 1 3
> Node 0, zone Normal 94 251 81 16 3 2 1 2 1 2 187
> Node 0, zone HighMem 113 88 47 36 18 5 4 3 2 0 268
> Node 1, zone HighMem 154 97 43 16 9 4 3 2 3 2 482
...
>
> I presume node 1 having only HighMem could be the reason ?

What does cpu_to_node() on each cpu say? Also, do you know why
num_possible_cpus() is 32, not 16?

Thanks.

--
tejun
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