vmscan: synchronous lumpy reclaim don't call congestion_wait()
in [Kernel]
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From: Minchan Kim on 2 Aug 2010 00:40 On Mon, Aug 2, 2010 at 1:13 PM, KOSAKI Motohiro <kosaki.motohiro(a)jp.fujitsu.com> wrote: >> Hi KOSAKI, >> >> On Sun, Aug 01, 2010 at 06:12:47PM +0900, KOSAKI Motohiro wrote: >> > rebased onto Wu's patch >> > >> > ---------------------------------------------- >> > From 35772ad03e202c1c9a2252de3a9d3715e30d180f Mon Sep 17 00:00:00 2001 >> > From: KOSAKI Motohiro <kosaki.motohiro(a)jp.fujitsu.com> >> > Date: Sun, 1 Aug 2010 17:23:41 +0900 >> > Subject: [PATCH] vmscan: synchronous lumpy reclaim don't call congestion_wait() >> > >> > congestion_wait() mean "waiting for number of requests in IO queue is >> > under congestion threshold". >> > That said, if the system have plenty dirty pages, flusher thread push >> > new request to IO queue conteniously. So, IO queue are not cleared >> > congestion status for a long time. thus, congestion_wait(HZ/10) is >> > almostly equivalent schedule_timeout(HZ/10). >> Just a nitpick. >> Why is it a problem? >> HZ/10 is upper bound we intended. �If is is rahter high, we can low it. >> But totally I agree on this patch. It would be better to remove it >> than lowing. > > because all of _unnecessary_ sleep is evil. the problem is, congestion_wait() > mean "wait until queue congestion will be cleared, iow, wait all of IO". > but we want to wait until _my_ IO finished. > > So, if flusher thread conteniously push new IO into the queue, that makes > big difference. > Agree. Please include this explanation in description to make it kind if you resent this patch. Thanks -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.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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