lkml.org 
[lkml]   [2011]   [Oct]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] Reduce vm_stat cacheline contention in __vm_enough_memory
    On Thu, 13 Oct 2011 10:54:30 -0500 (CDT)
    Christoph Lameter <cl@gentwo.org> 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.




    \
     
     \ /
      Last update: 2011-10-13 22:53    [W:0.021 / U:184.524 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site