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 E28096B01EE for ; Wed, 31 Mar 2010 01:53:32 -0400 (EDT) Received: from m4.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail5.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o2V5rUgg003270 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Wed, 31 Mar 2010 14:53:30 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 5939B45DE60 for ; Wed, 31 Mar 2010 14:53:30 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 1D48845DE6E for ; Wed, 31 Mar 2010 14:53:30 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 00BA51DB803F for ; Wed, 31 Mar 2010 14:53:30 +0900 (JST) Received: from m107.s.css.fujitsu.com (m107.s.css.fujitsu.com [10.249.87.107]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 9FAECE1800A for ; Wed, 31 Mar 2010 14:53:29 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH]vmscan: handle underflow for get_scan_ratio In-Reply-To: <20100331142708.039E.A69D9226@jp.fujitsu.com> References: <20100331045348.GA3396@sli10-desk.sh.intel.com> <20100331142708.039E.A69D9226@jp.fujitsu.com> Message-Id: <20100331145030.03A1.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Wed, 31 Mar 2010 14:53:27 +0900 (JST) Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: Shaohua Li , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "Wu, Fengguang" List-ID: > > 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. Oops, the above mention is wrong. sorry. only 1 page is still too big. because under streaming io workload, the number of scanning anon pages should be zero. this is very strong requirement. if not, backup operation will makes a lot of swapping out. Anyway, I'm digging this issue. > > 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. -- 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