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    SubjectRe: [RESEND][PATCH] mm: vmstats: tlb flush counters
    On Wed, 17 Jul 2013 09:21:00 +0200 Ingo Molnar <mingo@kernel.org> wrote:

    >
    > * Dave Hansen <dave@sr71.net> wrote:
    >
    > > I was investigating some TLB flush scaling issues and realized
    > > that we do not have any good methods for figuring out how many
    > > TLB flushes we are doing.
    > >
    > > It would be nice to be able to do these in generic code, but the
    > > arch-independent calls don't explicitly specify whether we
    > > actually need to do remote flushes or not. In the end, we really
    > > need to know if we actually _did_ global vs. local invalidations,
    > > so that leaves us with few options other than to muck with the
    > > counters from arch-specific code.

    Spose so, if you really think it's worth it. It's all downside for
    uniprocessor machines. And for architectures which don't implement the
    counters, of course.

    > > --- linux.git/include/linux/vm_event_item.h~tlb-vmstats 2013-07-16 16:41:56.478280438 -0700
    > > +++ linux.git-davehans/include/linux/vm_event_item.h 2013-07-16 16:41:56.483280658 -0700
    > > @@ -70,6 +70,11 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
    > > THP_ZERO_PAGE_ALLOC,
    > > THP_ZERO_PAGE_ALLOC_FAILED,
    > > #endif
    > >
    > > + NR_TLB_REMOTE_FLUSH, /* cpu tried to flush others' tlbs */
    > > + NR_TLB_REMOTE_FLUSH_RECEIVED,/* cpu received ipi for flush */
    > > + NR_TLB_LOCAL_FLUSH_ALL,
    > > + NR_TLB_LOCAL_FLUSH_ONE,
    > > + NR_TLB_LOCAL_FLUSH_ONE_KERNEL,
    >
    > Please fix the vertical alignment of comments.

    I looked - this isn't practical.

    It would be nice to actually document these things though. We don't
    *have* to squeeze the comment into the RHS.



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