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Date: Thu, 13 Oct 2011 13:50:32 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Christoph Lameter <cl@...two.org> Cc: Dimitri Sivanich <sivanich@....com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, Mel Gorman <mel@....ul.ie> Subject: Re: [PATCH] Reduce vm_stat cacheline contention in __vm_enough_memory On Thu, 13 Oct 2011 10:54:30 -0500 (CDT) Christoph Lameter <cl@...two.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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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