From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754440AbYAYDeW (ORCPT ); Thu, 24 Jan 2008 22:34:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752422AbYAYDeM (ORCPT ); Thu, 24 Jan 2008 22:34:12 -0500 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:39125 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752159AbYAYDeK (ORCPT ); Thu, 24 Jan 2008 22:34:10 -0500 Date: Fri, 25 Jan 2008 12:33:14 +0900 From: KOSAKI Motohiro To: =?ISO-2022-JP?B?IkRhbmllbCBTcBskQmlPGyhCZyI=?= Subject: Re: [RFC][PATCH 3/8] mem_notify v5: introduce /dev/mem_notify new device (the core of this patch series) Cc: kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Marcelo Tosatti" , "Rik van Riel" , "Andrew Morton" , "Alan Cox" In-Reply-To: References: <20080124132014.1769.KOSAKI.MOTOHIRO@jp.fujitsu.com> Message-Id: <20080125121032.1AAE.KOSAKI.MOTOHIRO@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-2022-JP" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.42 [ja] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Daniel > > +#define PROC_WAKEUP_GUARD (10*HZ) > [...] > > + timeout = info->last_proc_notify + PROC_WAKEUP_GUARD; > > If only one or a few processes are using the system I think 10 seconds > is a little long time to wait before they get the notification again. > Can we decrease this value? Or make it configurable under /proc? Or > make it lower with fewer users? Something like: Oh, that is very interesting issue. tank you good point out. after deep thinking, I understand my current implementation is fully stupid. current, worst case is below. 1. low end - many process of used only a bit memory(sh, cp etc..) exist. - 1 memory eater process exist(may be, it is fat browser) and it watching /dev/mem_notify. 2. high end - many process of used only a bit memory(sh, cp etc..) exist. - 1 memory eater process exist(may be, it is DB) and it watching /dev/mem_notify. the point is "only 1 process watch /dev/mem_notify", but not a few processor. I fix it with pleasure. > timeout = info->last_proc_notify + min(mem_notify_users, PROC_WAKEUP_GUARD); I like this formula. the rest problem is decide to default value when only 1 process watch /dev/mem_notify. What do you think it? and if my low end worst case situation doesn't match yours, Could you please explain your usage more? BTW: end up, We will add /proc configuration the future. but I think it is too early. sometimes configrable parameter prevent the discussion of nicer default value. Instead, I hope the default value changed by adjust your usage. - kosaki