From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id A32586B02E2 for ; Mon, 2 Aug 2010 00:13:27 -0400 (EDT) Received: from m1.gw.fujitsu.co.jp ([10.0.50.71]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o724DNcH005082 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Mon, 2 Aug 2010 13:13:24 +0900 Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id B04F345DE54 for ; Mon, 2 Aug 2010 13:13:23 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 8943645DE51 for ; Mon, 2 Aug 2010 13:13:23 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 67DD0EF8002 for ; Mon, 2 Aug 2010 13:13:23 +0900 (JST) Received: from m106.s.css.fujitsu.com (m106.s.css.fujitsu.com [10.249.87.106]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 191281DB804C for ; Mon, 2 Aug 2010 13:13:23 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH] vmscan: synchronous lumpy reclaim don't call congestion_wait() In-Reply-To: <20100801134117.GA2034@barrios-desktop> References: <20100801180751.4B0E.A69D9226@jp.fujitsu.com> <20100801134117.GA2034@barrios-desktop> Message-Id: <20100802131016.4F7D.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Mon, 2 Aug 2010 13:13:21 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: kosaki.motohiro@jp.fujitsu.com, 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: > 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 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org