Re: [PATCH 5/5] slub: Only IPI CPUs that have per cpu obj to flush

[Gilad Ben-Yossef]

On Mon, Sep 26, 2011 at 3:05 PM, Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx> wrote:


>> The problem with a per-cpu cpumask is that you need to disable
>> preemption over the whole for_each_online_cpu() scan and that's not
>> really sane on very large machines as that can easily take a very long
>> time indeed.
>
> hmm... I might be thick, but why disable the preemption with the
> per-cpu cpumask at all?
...
>
> Does that makes sense or have I've gone over board with this concept? :-)

Scratch that. The cpumask must be per cache or the patch doesn't make
sense at all.
So sadly the only sane place to put it is in struct kmem_cache.

I think we can still update the cpumask field without caring about
preemption for the reasons
stated above, but the per cache memory overhead is still there I'm afraid.

Gilad

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Gilad Ben-Yossef
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