Messages in this thread | | | Date | Wed, 10 Jun 2009 10:54:09 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 1/3] Reintroduce zone_reclaim_interval for when zone_reclaim() scans and fails to avoid CPU spinning at 100% on NUMA |
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On Wed, Jun 10, 2009 at 10:14:40AM +0800, Wu Fengguang wrote: > On Tue, Jun 09, 2009 at 11:06:19PM +0800, Mel Gorman wrote: > > On Tue, Jun 09, 2009 at 09:38:04PM +0800, Wu Fengguang wrote: > > > On Tue, Jun 09, 2009 at 05:40:50PM +0800, Mel Gorman wrote: > > > > > > > > Conceivably though, zone_reclaim_interval could automatically tune > > > > itself based on a heuristic like this if the administrator does not give > > > > a specific value. I think that would be an interesting follow on once > > > > we've brought back zone_reclaim_interval and get a feeling for how often > > > > it is actually used. > > > > > > Well I don't think that's good practice. There are heuristic > > > calculations all over the kernel. Shall we exporting parameters to > > > user space just because we are not absolutely sure? Or shall we ship > > > the heuristics and do adjustments based on feedbacks and only export > > > parameters when we find _known cases_ that cannot be covered by pure > > > heuristics? > > > > > > > Good question - I don't have a satisfactory answer but I intuitively find > > the zone_reclaim_interval easier to deal with than the heuristic. That said, > > I would prefer if neither was required. > > Yes - can we rely on the (improved) accounting to make our "failure feedback" > patches unnecessary? :) >
Am awaiting test results to answer that question :)
> Thanks, > Fengguang > > > In the patchset, I've added a counter for the number of times that the > > scan-avoidance heuristic fails. If the tmpfs problem has been resolved > > (patch with bug reporter, am awaiting test), I'll drop zone_reclaim_interval > > altogether and we'll use the counter to detect if/when this situation > > occurs again. >
-- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab
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