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 421756B01F9 for ; Tue, 30 Mar 2010 02:53:43 -0400 (EDT) Date: Tue, 30 Mar 2010 14:53:58 +0800 From: Shaohua Li Subject: Re: [PATCH]vmscan: handle underflow for get_scan_ratio Message-ID: <20100330065358.GA24828@sli10-desk.sh.intel.com> References: <20100330150453.8E9F.A69D9226@jp.fujitsu.com> <1269930756.17240.4.camel@sli10-desk.sh.intel.com> <20100330153750.8EA2.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100330153750.8EA2.A69D9226@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "Wu, Fengguang" List-ID: On Tue, Mar 30, 2010 at 02:40:07PM +0800, KOSAKI Motohiro wrote: > > On Tue, 2010-03-30 at 14:08 +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 > > attached. > > > and reproduce program? I'll digg it. > > our test is quite sample. mount tmpfs with double memory size and store several > > copies (memory size * 2/G) of kernel in tmpfs, and then do kernel build. > > for example, there is 3G memory and then tmpfs size is 6G and there is 6 > > kernel copy. > > Wow, tmpfs size > memsize! > > > > > Very unfortunately, this patch isn't acceptable. In past time, vmscan > > > had similar logic, but 1% swap-out made lots bug reports. > > can you elaborate this? > > Completely restore previous behavior (do full scan with priority 0) is > > ok too. > > This is a option. but we need to know the root cause anyway. I thought I mentioned the root cause in first mail. My debug shows recent_rotated[0] is big, but recent_rotated[1] is almost zero, which makes percent[0] 0. But you can double check too. -- 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