Re: [PATCH] use local_t for page statistics

[Nick Piggin]

Andrew Morton wrote:
> Benjamin LaHaise <bcrl@xxxxxxxxx> 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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