From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id F2D846B004A for ; Thu, 2 Sep 2010 06:04:54 -0400 (EDT) Received: from m5.gw.fujitsu.co.jp ([10.0.50.75]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o82A4qUG012131 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Thu, 2 Sep 2010 19:04:52 +0900 Received: from smail (m5 [127.0.0.1]) by outgoing.m5.gw.fujitsu.co.jp (Postfix) with ESMTP id 4384E45DE51 for ; Thu, 2 Sep 2010 19:04:52 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (s5.gw.fujitsu.co.jp [10.0.50.95]) by m5.gw.fujitsu.co.jp (Postfix) with ESMTP id 1FBFA45DE4F for ; Thu, 2 Sep 2010 19:04:52 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id 086631DB803C for ; Thu, 2 Sep 2010 19:04:52 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id B87101DB8038 for ; Thu, 2 Sep 2010 19:04:51 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH] vmscan,tmpfs: treat used once pages on tmpfs as used once In-Reply-To: References: <20100901103653.974C.A69D9226@jp.fujitsu.com> Message-Id: <20100902185926.B64E.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Thu, 2 Sep 2010 19:04:50 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: kosaki.motohiro@jp.fujitsu.com, Hugh Dickins , Johannes Weiner , Rik van Riel , LKML , linux-mm , Andrew Morton List-ID: > Hi KOSAKI, > > On Wed, Sep 1, 2010 at 10:37 AM, KOSAKI Motohiro > wrote: > > When a page has PG_referenced, shrink_page_list() discard it only > > if it is no dirty. This rule works completely fine if the backend > > filesystem is regular one. PG_dirty is good signal that it was used > > recently because flusher thread clean pages periodically. In addition, > > page writeback is costly rather than simple page discard. > > > > However, When a page is on tmpfs, this heuristic don't works because > > flusher thread don't writeback tmpfs pages. then, tmpfs pages always > > rotate lru twice at least and it makes unnecessary lru churn. Merely > > tmpfs streaming io shouldn't cause large anonymous page swap-out. > > It seem to make sense. > But the why admin use tmps is to keep the contents in memory as far as > possible than other's file system. > But this patch has a possibility for tmpfs pages to reclaim early than > old behavior. > > I admit this routine's goal is not to protect tmpfs page from too early reclaim. > But at least, it would have affected until now. > If it is, we might need other demotion prevent mechanism to protect tmpfs pages. > Is split LRU enough? (I mean we consider tmpfs pages as anonymous > which is hard to reclaim than file backed pages). I think so. Split-LRU provide priotize anon rather than regular file. and old behavior is obvious strange. streaming io tolerance is one of fundamental VM requirement. So, I think current one is only historical reason. > > I don't mean to oppose this patch and I don't have a any number to > insist on my opinion. > Just what I want is that let's think about it more carefully and > listen other's opinions. :) > > Thanks for good suggestion. > > -- > Kind regards, > Minchan Kim -- 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