Messages in this thread | | | Date | Thu, 11 Apr 2013 10:10:44 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 0/10] Reduce system disruption due to kswapd V2 |
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On Wed, Apr 10, 2013 at 03:28:32PM -0700, dormando wrote: > > On Tue, Apr 09, 2013 at 05:27:18PM +0000, Christoph Lameter wrote: > > > One additional measure that may be useful is to make kswapd prefer one > > > specific processor on a socket. Two benefits arise from that: > > > > > > 1. Better use of cpu caches and therefore higher speed, less > > > serialization. > > > > > > > Considering the volume of pages that kswapd can scan when it's active > > I would expect that it trashes its cache anyway. The L1 cache would be > > flushed after scanning struct pages for just a few MB of memory. > > > > > 2. Reduction of the disturbances to one processor. > > > > > > > I've never checked it but I would have expected kswapd to stay on the > > same processor for significant periods of time. Have you experienced > > problems where kswapd bounces around on CPUs within a node causing > > workload disruption? > > When kswapd shares the same CPU as our main process it causes a measurable > drop in response time (graphs show tiny spikes at the same time memory is > freed). Would be nice to be able to ensure it runs on a different core > than our latency sensitive processes at least. We can pin processes to > subsets of cores but I don't think there's a way to keep kswapd from > waking up on any of them?
I've never tried it myself but does the following work?
taskset -p MASK `pidof kswapd`
where MASK is a cpumask describing what CPUs kswapd can run on? Obviously care should be taken to ensure that you bind kswapd to a CPU running on the node kswapd cares about.
-- Mel Gorman SUSE Labs
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