> 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@xxxxxxxxxxxxxx> > > 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. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>