From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751822Ab1GZGjG (ORCPT ); Tue, 26 Jul 2011 02:39:06 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:48959 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750827Ab1GZGjC (ORCPT ); Tue, 26 Jul 2011 02:39:02 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Message-ID: <4E2E6102.3060600@jp.fujitsu.com> Date: Tue, 26 Jul 2011 15:38:58 +0900 From: KOSAKI Motohiro User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:5.0) Gecko/20110624 Thunderbird/5.0 MIME-Version: 1.0 To: yong.zhang0@gmail.com CC: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, kobayashi.kk@ncos.nec.co.jp Subject: Re: [PATCH] proc/softirqs: only show state for online cpus References: <1311599418-1915-1-git-send-email-yong.zhang0@gmail.com> <4E2E507F.7030607@jp.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2011/07/26 15:14), Yong Zhang wrote: > 2011/7/26 KOSAKI Motohiro : >>> Like /proc/interrupts, no need to output data for nobody. >>> >>> Signed-off-by: Yong Zhang >>> Cc: Andrew Morton >>> Cc: Keika Kobayashi >>> Cc: KOSAKI Motohiro >> >> If the cpu never be onlined, its statistics always 0. Then, it definitely > > Yeah, so your screen may contain noise. One question. Is this big matter? Who see /proc/softirqs and /proc/interrupts directly? (i.e. by 'cat' command). >> no value. In the other hand, if the cpu was offlined dynamically, we don't >> know the user want to know the cpus's statistics or not. > > Same to /proc/interrupts :) > > IMHO, if user want to check the value of offline-cpu, maybe that means > he want to check the state of the whole system, /proc/stat should be the > right choice. /proc/{softirqs,interrupts} is just for immediate state. > >> Anyway, it's incompatibility change. > > Yup, I should have marked the patch with RFC :) And I should have remarked I don't dislike this patch so strongly, so if kobayashi-san who original /proc/softirqs author ack you, I'm going to second him. Offtopic, /proc/interrupt should be protected by get_online_cpus(). Otherwise the header (i.e. cpu number) and the actual statistics fields can be mismatched likes following. Am I missing something? CPU0 CPU1 CPU2 0: 14286646 14747155 0 IO-APIC-edge timer 1: 6 6 IO-APIC-edge i8042 ^ | cpu2 was offlined dynamically at the same time.