From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id 019486B02E4 for ; Mon, 2 Aug 2010 00:38:37 -0400 (EDT) Received: by gwj16 with SMTP id 16so1509870gwj.14 for ; Sun, 01 Aug 2010 21:38:29 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20100802131016.4F7D.A69D9226@jp.fujitsu.com> References: <20100801180751.4B0E.A69D9226@jp.fujitsu.com> <20100801134117.GA2034@barrios-desktop> <20100802131016.4F7D.A69D9226@jp.fujitsu.com> Date: Mon, 2 Aug 2010 13:38:29 +0900 Message-ID: Subject: Re: [PATCH] vmscan: synchronous lumpy reclaim don't call congestion_wait() From: Minchan Kim Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: Wu Fengguang , Andrew Morton , Mel Gorman , Andy Whitcroft , Rik van Riel , Christoph Hellwig , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , Dave Chinner , Chris Mason , Nick Piggin , Johannes Weiner , KAMEZAWA Hiroyuki , Andrea Arcangeli , Andreas Mohr , Bill Davidsen , Ben Gamari List-ID: On Mon, Aug 2, 2010 at 1:13 PM, KOSAKI Motohiro 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 >> > Date: Sun, 1 Aug 2010 17:23:41 +0900 >> > Subject: [PATCH] vmscan: synchronous lumpy reclaim don't call congesti= on_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. =A0If 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_wa= it() > 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 --=20 Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org