Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752690Ab0HBEic (ORCPT ); Mon, 2 Aug 2010 00:38:32 -0400 Received: from mail-yx0-f174.google.com ([209.85.213.174]:39747 "EHLO mail-yx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752499Ab0HBEia convert rfc822-to-8bit (ORCPT ); Mon, 2 Aug 2010 00:38:30 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=EG7Uu8ake7Nf1ltnIrUANywnHeepLP0OboLTWTBkXmQTA+0WKUkavYX2OAgJznMAEF sOktEiqhQAOyuNsX7G2J6M5PasFL4XvMujIwpCWDxi87ZmUJKtVGZSc5ap1yxzgwMr/1 5PhHSZg2E1+vc6pqrqcLDoJA89agCU6ixlPD8= 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 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 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1791 Lines: 46 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 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/