Re: Re: [RFC] [PATCH 9/9] memcg: percpu page cgroup lookup cache

From: kamezawa . hiroyu
Date: Thu Sep 11 2008 - 08:58:35 EST

----- Original Message -----
>On Thursday 11 September 2008 21:24, KAMEZAWA Hiroyuki wrote:
>> Use per-cpu cache for fast access to page_cgroup.
>> This patch is for making fastpath faster.
>> Because page_cgroup is accessed when the page is allocated/freed,
>> we can assume several of continuous page_cgroup will be accessed soon.
>> (If not interleaved on NUMA...but in such case, alloc/free itself is slow.)
>> We cache some set of page_cgroup's base pointer on per-cpu area and
>> use it when we hit.
>> TODO:
>> - memory/cpu hotplug support.
>How much does this help?
1-2% in unixbench's test (in 0/9) on 2core/1socket x86-64/SMP host.
(cpu is not the newest one.)
This per-cpu covers 32 * 128MB=4GB of area.
Using 256 bytes(32 entry) is over-kill ?

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