Messages in this thread | | | Date | Thu, 13 Oct 2011 13:50:32 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] Reduce vm_stat cacheline contention in __vm_enough_memory |
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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.
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