Messages in this thread | | | Date | Fri, 6 Jan 2006 23:00:29 -0200 | From | Marcelo Tosatti <> | Subject | Re: [PATCH] use local_t for page statistics |
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On Fri, Jan 06, 2006 at 04:33:13PM -0800, 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?
Don't think so - local_t operations are performed atomically, which is not required for most hotpath page statistics operations since proper locks are already held.
What is wanted for these cases are simple inc/dec (non-atomic) instructions, which is what Nick's patch does by introducing __mod_page_state.
Ben, have you tested mm-page_state-opt.patch? It should get rid of most "flags" save/restore on stack.
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