Re: [PATCH] use local_t for page statistics

Nick Piggin
2006-01-07T02:52:51Z

Andrew Morton wrote:
> Benjamin LaHaise <bcrl@kvack.org> wrote:
>
>>The patch below converts the mm page_states counters to use local_t.
>>mod_page_state shows up in a few profiles on x86 and x86-64 due to the
>>disable/enable interrupts operations touching the flags register. On
>>both my laptop (Pentium M) and P4 test box this results in about 10
>>additional /bin/bash -c exit 0 executions per second (P4 went from ~759/s
>>to ~771/s). Tested on x86 and x86-64. Oh, also add a pgcow statistic
>>for the number of COW page faults.
>
>
> Bah. I think this is a better approach than the just-merged
> mm-page_state-opt.patch, so I should revert that patch first?
>

No. On many load/store architectures there is no good way to do local_t,
so something like ppc32 or ia64 just uses all atomic operations for
local_t, and ppc64 uses 3 counters per-cpu thus tripling the cache
footprint.

Nick

--
SUSE Labs, Novell Inc.

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