From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id 1FD7D6B003D for ; Thu, 30 Apr 2009 05:48:26 -0400 (EDT) Received: from m3.gw.fujitsu.co.jp ([10.0.50.73]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n3U9nA6K007345 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Thu, 30 Apr 2009 18:49:10 +0900 Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id EA01B45DD7D for ; Thu, 30 Apr 2009 18:49:09 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id C902045DD7E for ; Thu, 30 Apr 2009 18:49:09 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id A250E1DB803F for ; Thu, 30 Apr 2009 18:49:09 +0900 (JST) Received: from ml13.s.css.fujitsu.com (ml13.s.css.fujitsu.com [10.249.87.103]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 45AC31DB8040 for ; Thu, 30 Apr 2009 18:49:09 +0900 (JST) Date: Thu, 30 Apr 2009 18:47:38 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH] memcg: fix stale swap cache leak v5 Message-Id: <20090430184738.752858ea.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090430094252.GG4430@balbir.in.ibm.com> References: <20090430161627.0ccce565.kamezawa.hiroyu@jp.fujitsu.com> <20090430163539.7a882cef.kamezawa.hiroyu@jp.fujitsu.com> <20090430180426.25ae2fa6.kamezawa.hiroyu@jp.fujitsu.com> <20090430094252.GG4430@balbir.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: balbir@linux.vnet.ibm.com Cc: "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "nishimura@mxp.nes.nec.co.jp" , "akpm@linux-foundation.org" , "hugh@veritas.com" List-ID: On Thu, 30 Apr 2009 15:12:52 +0530 Balbir Singh wrote: > * KAMEZAWA Hiroyuki [2009-04-30 18:04:26]: > > > On Thu, 30 Apr 2009 16:35:39 +0900 > > KAMEZAWA Hiroyuki wrote: > > > > > On Thu, 30 Apr 2009 16:16:27 +0900 > > > KAMEZAWA Hiroyuki wrote: > > > > > > > This is v5 but all codes are rewritten. > > > > > > > > After this patch, when memcg is used, > > > > 1. page's swapcount is checked after I/O (without locks). If the page is > > > > stale swap cache, freeing routine will be scheduled. > > > > 2. vmscan.c calls try_to_free_swap() when __remove_mapping() fails. > > > > > > > > Works well for me. no extra resources and no races. > > > > > > > > Because my office will be closed until May/7, I'll not be able to make a > > > > response. Posting this for showing what I think of now. > > > > > > > I found a hole immediately after posted this...sorry. plz ignore this patch/ > > > see you again in the next month. > > > > > I'm now wondering to disable "swapin readahed" completely when memcg is used... > > Then, half of the problems will go away immediately. > > And it's not so bad to try to free swapcache if swap writeback ends. Then, another > > half will go away... > > > > Could you clarify? Will memcg not account for swapin readahead pages? > swapin-readahead pages are _not_ accounted now. (And I think _never_) But has race and leak swp_entry account until global LRU runs. "Don't do swapin-readahead, at all" will remove following race completely. == CPU0 CPU1 free_swap_and_cache() read_swapcache_async() == swp_entry to be freed will not be read-in. I think there will no performance regression in _usual_ case even if no readahead. But has no number yet. Thanks, -Kame -- 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