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    SubjectRe: [PATCH] Reduce vm_stat cacheline contention in __vm_enough_memory
    On Thu, 13 Oct 2011 10:54:30 -0500 (CDT)
    Christoph Lameter <> wrote:

    > On Thu, 13 Oct 2011, Dimitri Sivanich wrote:
    > > > increase the allowed delta per zone if frequent updates occur via the
    > > > overflow checks in vmstat.c. See calculate_*_threshold there.
    > >
    > > I tried changing the threshold in both directions, with slower throughput in
    > > both cases.
    > If that is the case check for the vm_stat cacheline being shared with
    > another hot kernel variable variable. Maybe that causes cacheline
    > eviction.

    yup. `nm -n vmlinux'.

    > If there are no updates occurring for a while (due to increased deltas
    > and/or vmstat updates) then the vm_stat cacheline should be able to stay
    > in shared mode in multiple processors and the performance should increase.

    We could cacheline align vm_stat[]. But the thing is pretty small - we
    couild put each entry in its own cacheline.

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      Last update: 2011-10-13 22:53    [W:0.021 / U:3.756 seconds]
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