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Date: Sun, 5 Jul 2009 18:51:58 +0800 From: Wu Fengguang <fengguang.wu@...il.com> To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> Cc: Rik van Riel <riel@...hat.com>, David Woodhouse <dwmw2@...radead.org>, David Howells <dhowells@...hat.com>, Minchan Kim <minchan.kim@...il.com>, Mel Gorman <mel@....ul.ie>, Johannes Weiner <hannes@...xchg.org>, Andrew Morton <akpm@...ux-foundation.org>, LKML <linux-kernel@...r.kernel.org>, Christoph Lameter <cl@...ux-foundation.org>, "peterz@...radead.org" <peterz@...radead.org>, "tytso@....edu" <tytso@....edu>, "linux-mm@...ck.org" <linux-mm@...ck.org>, "elladan@...imo.com" <elladan@...imo.com>, "npiggin@...e.de" <npiggin@...e.de>, "Barnes, Jesse" <jesse.barnes@...el.com> Subject: Re: Found the commit that causes the OOMs On Sun, Jul 05, 2009 at 07:38:54PM +0900, KOSAKI Motohiro wrote: > > >> OK. thanks. > > >> I plan to submit this patch after small more tests. it is useful for OOM analysis. > > > > > > It is also useful for throttling page reclaim. > > > > > > If more than half of the inactive pages in a zone are > > > isolated, we are probably beyond the point where adding > > > additional reclaim processes will do more harm than good. > > > > Maybe we can try limiting the isolation phase of direct reclaims to > > one per CPU? > > > > mutex_lock(per_cpu_lock); > > isolate_pages(); > > shrink_page_list(); > > put_back_pages(); > > mutex_unlock(per_cpu_lock); > > > > This way the isolated pages as well as major parts of direct reclaims > > will be bounded by CPU numbers. The added overheads should be trivial > > comparing to the reclaim costs. > > hm, this idea makes performance degression on few CPU machine, I think. Yes, this is also my big worry. But one possible workaround is to allow N direct reclaims per CPU. > e.g. > if system have only one cpu and sysmtem makes lumpy reclaim, lumpy reclaim > makes synchronous pageout and it makes very long waiting time. We can temporarily drop the lock during the writeback waiting. 0-order reclaims shall not be blocked by ongoing high order reclaims. > I suspect per-cpu decision is not useful in this area. Maybe. I'm just proposing one more possible way to choose from :) Thanks, Fengguang -- 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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