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 A981A6B0047 for ; Thu, 14 Jan 2010 21:33:56 -0500 (EST) Received: from m1.gw.fujitsu.co.jp ([10.0.50.71]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o0F2XrGA011452 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Fri, 15 Jan 2010 11:33:53 +0900 Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 2C0DC45DE5B for ; Fri, 15 Jan 2010 11:33:53 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id B992C45DE52 for ; Fri, 15 Jan 2010 11:33:52 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 93612E38002 for ; Fri, 15 Jan 2010 11:33:52 +0900 (JST) Received: from m107.s.css.fujitsu.com (m107.s.css.fujitsu.com [10.249.87.107]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 452941DB8042 for ; Fri, 15 Jan 2010 11:33:52 +0900 (JST) Date: Fri, 15 Jan 2010 11:30:35 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [resend][PATCH] mm: Restore zone->all_unreclaimable to independence word Message-Id: <20100115113035.0acbb3dc.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20100114151959.2c46ee79.akpm@linux-foundation.org> References: <20100114103332.D71B.A69D9226@jp.fujitsu.com> <20100114161311.673B.A69D9226@jp.fujitsu.com> <20100114083229.GA7860@localhost> <20100114151959.2c46ee79.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: Wu Fengguang , KOSAKI Motohiro , David Rientjes , LKML , linux-mm , Minchan Kim , Huang Shijie List-ID: On Thu, 14 Jan 2010 15:19:59 -0800 Andrew Morton wrote: > On Thu, 14 Jan 2010 16:32:29 +0800 > Wu Fengguang wrote: > > > On Thu, Jan 14, 2010 at 03:14:10PM +0800, KOSAKI Motohiro wrote: > > > > On Thu, 14 Jan 2010, KOSAKI Motohiro wrote: > > > > > > > > > commit e815af95 (change all_unreclaimable zone member to flags) chage > > > > > all_unreclaimable member to bit flag. but It have undesireble side > > > > > effect. > > > > > free_one_page() is one of most hot path in linux kernel and increasing > > > > > atomic ops in it can reduce kernel performance a bit. > > > > > > > > > > Thus, this patch revert such commit partially. at least > > > > > all_unreclaimable shouldn't share memory word with other zone flags. > > > > > > > > > > > > > I still think you need to quantify this; saying you don't have a large > > > > enough of a machine that will benefit from it isn't really a rationale for > > > > the lack of any data supporting your claim. We should be basing VM > > > > changes on data, not on speculation that there's a measurable impact > > > > here. > > > > > > > > Perhaps you could ask a colleague or another hacker to run a benchmark for > > > > you so that the changelog is complete? > > > > > > ok, fair. although I dislike current unnecessary atomic-ops. > > > I'll pending this patch until get good data. > > > > I think it's a reasonable expectation to help large boxes. > > > > What we can do now, is to measure if it hurts mainline SMP > > boxes. If not, we are set on doing the patch :) > > yup, the effects of the change might be hard to measure. Not that one > shouldn't try! > > But sometimes we just have to do a best-effort change based upon theory > and past experience. > > Speaking of which... > > : --- a/include/linux/mmzone.h > : +++ b/include/linux/mmzone.h > : @@ -341,6 +341,7 @@ struct zone { > : > : unsigned long pages_scanned; /* since last reclaim */ > : unsigned long flags; /* zone flags, see below */ > : + int all_unreclaimable; /* All pages pinned */ > : > : /* Zone statistics */ > : atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS]; > > Was that the best place to put the field? It adds four bytes of > padding to the zone, hence is suboptimal from a cache utilisation point > of view. > > It might also be that we can place this field closed in memory to other > fields which are being manipulated at the same time as > all_unreclaimable, hm? > How about the same line where zone->lock is ? 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