Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752691Ab0ARBzc (ORCPT ); Sun, 17 Jan 2010 20:55:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752136Ab0ARBzb (ORCPT ); Sun, 17 Jan 2010 20:55:31 -0500 Received: from mail-pw0-f42.google.com ([209.85.160.42]:33560 "EHLO mail-pw0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751463Ab0ARBza convert rfc822-to-8bit (ORCPT ); Sun, 17 Jan 2010 20:55:30 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=S/DZ1g4/HOZYS0W5vV3HkeP2ouKuH2xc0ZorhIn0tqW9aDL/qckUtahtHfF52qzDj0 jPnGrBadjJywBcQUuzilPQhUNK/KjMVXQAhTfStzBmh3Q/YSrLKaB1EA7lH+dNte+VCo 6gOou01IOuTGz3qUWo1SBn2TL/lTq0ZnqiRMU= MIME-Version: 1.0 In-Reply-To: <20100118100359.AE22.A69D9226@jp.fujitsu.com> References: <20100114141735.672B.A69D9226@jp.fujitsu.com> <28c262361001150923l138f6805t22546887bf81b283@mail.gmail.com> <20100118100359.AE22.A69D9226@jp.fujitsu.com> Date: Mon, 18 Jan 2010 10:47:20 +0900 Message-ID: <28c262361001171747w450c8fd8j4daf84b72fb68e1a@mail.gmail.com> Subject: Re: [PATCH 2/3][v2] vmstat: add anon_scan_ratio field to zoneinfo From: Minchan Kim To: KOSAKI Motohiro Cc: LKML , linux-mm , Andrew Morton , Balbir Singh , KAMEZAWA Hiroyuki , Rik van Riel Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2436 Lines: 69 Hi, KOSAKI. On Mon, Jan 18, 2010 at 10:04 AM, KOSAKI Motohiro wrote: >> Hi, KOSAKI. >> >> On Thu, Jan 14, 2010 at 2:18 PM, KOSAKI Motohiro >> wrote: >> >> > Well. zone->lock and zone->lru_lock should be not taked at the same time. >> >> >> >> I looked over the code since I am out of office. >> >> I can't find any locking problem zone->lock and zone->lru_lock. >> >> Do you know any locking order problem? >> >> Could you explain it with call graph if you don't mind? >> >> >> >> I am out of office by tomorrow so I can't reply quickly. >> >> Sorry for late reponse. >> > >> > This is not lock order issue. both zone->lock and zone->lru_lock are >> > hotpath lock. then, same tame grabbing might cause performance impact. >> >> Sorry for late response. >> >> Your patch makes get_anon_scan_ratio of zoneinfo stale. >> What you said about performance impact is effective when VM pressure high. >> I think stale data is all right normally. >> But when VM pressure is high and we want to see the information in zoneinfo( >> this case is what you said), stale data is not a good, I think. >> >> If it's not a strong argue, I want to use old get_scan_ratio >> in get_anon_scan_ratio. > > please looks such function again. > > usally we use recent_rotated/recent_scanned ratio. then following > decreasing doesn't change any scan-ratio meaning. it only prevent > stat overflow. It has a primary role that floating average as well as prevenitng overflow. :) So, It's important. > >        if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { >                spin_lock_irq(&zone->lru_lock); >                reclaim_stat->recent_scanned[0] /= 2; >                reclaim_stat->recent_rotated[0] /= 2; >                spin_unlock_irq(&zone->lru_lock); >        } > > > So, I don't think current implementation can show stale data. It can make stale data when high memory pressure happens. > > Thanks. > Moreever, I don't want to make complicate thing(ie, need_update) than old if it doesn't have some benefit.(I think lru_lock isn't big overhead) -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/