Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752233Ab0HBEN3 (ORCPT ); Mon, 2 Aug 2010 00:13:29 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:37601 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751255Ab0HBEN2 (ORCPT ); Mon, 2 Aug 2010 00:13:28 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Minchan Kim Subject: Re: [PATCH] vmscan: synchronous lumpy reclaim don't call congestion_wait() 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 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 X-Mailer: Becky! ver. 2.50.07 [ja] Date: Mon, 2 Aug 2010 13:13:21 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1551 Lines: 38 > 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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/