From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5BBA0C0044C for ; Mon, 29 Oct 2018 21:35:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1AE2E2087A for ; Mon, 29 Oct 2018 21:35:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1AE2E2087A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727650AbeJ3GZr (ORCPT ); Tue, 30 Oct 2018 02:25:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52362 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726568AbeJ3GZr (ORCPT ); Tue, 30 Oct 2018 02:25:47 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BC6933001975; Mon, 29 Oct 2018 21:35:16 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-8.bos.redhat.com [10.18.17.8]) by smtp.corp.redhat.com (Postfix) with ESMTP id 15C9F2BFEF; Mon, 29 Oct 2018 21:35:16 +0000 (UTC) Subject: Re: [PATCH] fs/proc: introduce /proc/stat2 file To: Vito Caputo Cc: Davidlohr Bueso , akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Davidlohr Bueso References: <20181029192521.23059-1-dave@stgolabs.net> <0afed890-7c5a-93ee-cdb9-e30775bd9cf1@redhat.com> <20181029200050.iejuxckzbm742dmw@linux-r8p5> <3c5ba85b-5114-c751-0114-ac2cb64c02ea@redhat.com> <20181029203818.pot26ewxbncfrnua@linux-r8p5> <20181029212314.nwruqg6au23ebqlu@shells.gnugeneration.com> From: Waiman Long Organization: Red Hat Message-ID: <492f93c1-e062-f699-8c8c-c2277fd3fbb0@redhat.com> Date: Mon, 29 Oct 2018 17:35:15 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20181029212314.nwruqg6au23ebqlu@shells.gnugeneration.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Mon, 29 Oct 2018 21:35:16 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/29/2018 05:23 PM, Vito Caputo wrote: > On Mon, Oct 29, 2018 at 04:59:03PM -0400, Waiman Long wrote: >> On 10/29/2018 04:38 PM, Davidlohr Bueso wrote: >>> On Mon, 29 Oct 2018, Waiman Long wrote: >>> >>>> BTW, since you are making stat2 compatible with stat, will that be >>>> easier from the user API perspective if we use a sysctl parameter to >>>> turn on and off IRQs reporting for /proc/stat, for example? >>> For one /proc/stat is also common for debugging envs (ie: performance) >>> and I fear that if a tunnable modifies the behavior of the output, we >>> it might never be usable again (at least not without having users also >>> now consider the systctl parameter). Making it dynamic I think is not >>> worth it. >>> >>> Thanks, >>> Davidlohr >> This is just a matter if it is easier for users to modify their code to >> use /proc/stat2 or turning on a sysctl parameter. Again, this will >> certainly depend on the circumstances. >> > I wonder if it makes sense to introduce a more general mechanism for > toggling subfields in proc files. Extended attributes could probably be > abused to key the subfields, write a 1 or 0 to well-known names for > toggling them on a per-fd basis via fsetxattr. > > For this particular case the program would just have to add code like: > > int zero = 0; > fsetxattr(proc_stat_fd, "intr", &zero, sizeof(zero), XATTR_REPLACE); > > Just putting it out there. I've certainly wanted an ability to noop > fields before where I was polling proc frequently and skipping the bulk > of what was there but syscpu was still rather high. > > I'm definitely not in favor of just adding another stat file that is the > same format as the existing one with the intrs zeroed out. It's a dirty > hack; fine for your local needs but too gross for upstream IMHO. > > Regards, > Vito Caputo Does procfs allow extended attributes? I am not sure if using extended attributes is a usual practice for doing this kind of control on a procfs file. Cheers, Longman