From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932477Ab0CaGA4 (ORCPT ); Wed, 31 Mar 2010 02:00:56 -0400 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:37395 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753945Ab0CaGAz (ORCPT ); Wed, 31 Mar 2010 02:00:55 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Wu Fengguang Subject: Re: [PATCH]vmscan: handle underflow for get_scan_ratio Cc: kosaki.motohiro@jp.fujitsu.com, "Li, Shaohua" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" In-Reply-To: <20100331055108.GA21963@localhost> References: <20100331142708.039E.A69D9226@jp.fujitsu.com> <20100331055108.GA21963@localhost> Message-Id: <20100331145602.03A7.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: Wed, 31 Mar 2010 15:00:52 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > KOSAKI-san, > > On Wed, Mar 31, 2010 at 01:38:12PM +0800, KOSAKI Motohiro wrote: > > > On Tue, Mar 30, 2010 at 02:08:53PM +0800, KOSAKI Motohiro wrote: > > > > Hi > > > > > > > > > Commit 84b18490d1f1bc7ed5095c929f78bc002eb70f26 introduces a regression. > > > > > With it, our tmpfs test always oom. The test has a lot of rotated anon > > > > > pages and cause percent[0] zero. Actually the percent[0] is a very small > > > > > value, but our calculation round it to zero. The commit makes vmscan > > > > > completely skip anon pages and cause oops. > > > > > An option is if percent[x] is zero in get_scan_ratio(), forces it > > > > > to 1. See below patch. > > > > > But the offending commit still changes behavior. Without the commit, we scan > > > > > all pages if priority is zero, below patch doesn't fix this. Don't know if > > > > > It's required to fix this too. > > > > > > > > Can you please post your /proc/meminfo and reproduce program? I'll digg it. > > > > > > > > Very unfortunately, this patch isn't acceptable. In past time, vmscan > > > > had similar logic, but 1% swap-out made lots bug reports. > > > if 1% is still big, how about below patch? > > > > This patch makes a lot of sense than previous. however I think <1% anon ratio > > shouldn't happen anyway because file lru doesn't have reclaimable pages. > > <1% seems no good reclaim rate. > > > > perhaps I'll take your patch for stable tree. but we need to attack the root > > cause. iow, I guess we need to fix scan ratio equation itself. > > I tend to regard this patch as a general improvement for both > .33-stable and .34. > > I do agree with you that it's desirable to do more test&analyze and > check further for possibly hidden problems. Yeah, I don't want ignore .33-stable too. if I can't find the root cause in 2-3 days, I'll revert guilty patch anyway.