Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753718Ab0GZQaX (ORCPT ); Mon, 26 Jul 2010 12:30:23 -0400 Received: from mail-px0-f174.google.com ([209.85.212.174]:36918 "EHLO mail-px0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752485Ab0GZQaV (ORCPT ); Mon, 26 Jul 2010 12:30:21 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:content-transfer-encoding :in-reply-to:user-agent; b=FIaXUp0ke5Zx2ELmQP3XOs8722x1Ja22JDuDWoDq9R0bV5hQiExw0xqah5YygG3vga c1Re8v69N1HYVtihFhM2z/TSUFkvT0Fw5lj2PT4VoAlk87LmSLeobYhfjzRQJEKz6jio TJPHamLOvpb1K21dRkDbKoWtlQ9reI/K1lfOQ= Date: Tue, 27 Jul 2010 01:30:11 +0900 From: Minchan Kim To: Wu Fengguang Cc: KOSAKI Motohiro , Mel Gorman , Christoph Hellwig , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , Dave Chinner , Chris Mason , Nick Piggin , Rik van Riel , Johannes Weiner , KAMEZAWA Hiroyuki , Andrew Morton , Andrea Arcangeli Subject: Re: [PATCH 7/8] writeback: sync old inodes first in background writeback Message-ID: <20100726163011.GA23467@barrios-desktop> References: <20100723094515.GD5043@localhost> <20100723105719.GE5300@csn.ul.ie> <20100725192955.40D5.A69D9226@jp.fujitsu.com> <20100725120345.GA1817@barrios-desktop> <20100726032755.GB7668@localhost> <20100726043709.GC7668@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20100726043709.GC7668@localhost> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3229 Lines: 72 On Mon, Jul 26, 2010 at 12:37:09PM +0800, Wu Fengguang wrote: > On Mon, Jul 26, 2010 at 12:11:59PM +0800, Minchan Kim wrote: > > On Mon, Jul 26, 2010 at 12:27 PM, Wu Fengguang wrote: > > > On Sun, Jul 25, 2010 at 08:03:45PM +0800, Minchan Kim wrote: > > >> On Sun, Jul 25, 2010 at 07:43:20PM +0900, KOSAKI Motohiro wrote: > > >> > Hi > > >> > > > >> > sorry for the delay. > > >> > > > >> > > Will you be picking it up or should I? The changelog should be more or less > > >> > > the same as yours and consider it > > >> > > > > >> > > Signed-off-by: Mel Gorman > > >> > > > > >> > > It'd be nice if the original tester is still knocking around and willing > > >> > > to confirm the patch resolves his/her problem. I am running this patch on > > >> > > my desktop at the moment and it does feel a little smoother but it might be > > >> > > my imagination. I had trouble with odd stalls that I never pinned down and > > >> > > was attributing to the machine being commonly heavily loaded but I haven't > > >> > > noticed them today. > > >> > > > > >> > > It also needs an Acked-by or Reviewed-by from Kosaki Motohiro as it alters > > >> > > logic he introduced in commit [78dc583: vmscan: low order lumpy reclaim also > > >> > > should use PAGEOUT_IO_SYNC] > > >> > > > >> > My reviewing doesn't found any bug. however I think original thread have too many guess > > >> > and we need to know reproduce way and confirm it. > > >> > > > >> > At least, we need three confirms. > > >> > ?o original issue is still there? > > >> > ?o DEF_PRIORITY/3 is best value? > > >> > > >> I agree. Wu, how do you determine DEF_PRIORITY/3 of LRU? > > >> I guess system has 512M and 22M writeback pages. > > >> So you may determine it for skipping max 32M writeback pages. > > >> Is right? > > > > > > For 512M mem, DEF_PRIORITY/3 means 32M dirty _or_ writeback pages. > > > Because shrink_inactive_list() first calls > > > shrink_page_list(PAGEOUT_IO_ASYNC) then optionally > > > shrink_page_list(PAGEOUT_IO_SYNC), so dirty pages will first be > > > converted to writeback pages and then optionally be waited on. > > > > > > The dirty/writeback pages may go up to 512M*20% = 100M. So 32M looks > > > a reasonable value. > > > > Why do you think it's a reasonable value? > > I mean why isn't it good 12.5% or 3.125%? Why do you select 6.25%? > > I am not against you. Just out of curiosity and requires more explanation. > > It might be thing _only I_ don't know. :( > > It's more or less random selected. I'm also OK with 3.125%. It's an > threshold to turn on some _last resort_ mechanism, so don't need to be > optimal.. Okay. Why I had a question is that I don't want to add new magic value in VM without detailed comment. While I review the source code, I always suffer form it. :( Now we have a great tool called 'git'. Please write down why we select that number detaily when we add new magic value. :) Thanks, Wu. -- 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/