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=-1.0 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 6F06AC0044C for ; Wed, 7 Nov 2018 16:31:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E9852086C for ; Wed, 7 Nov 2018 16:31:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E9852086C 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 S1731348AbeKHCCl (ORCPT ); Wed, 7 Nov 2018 21:02:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60608 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727312AbeKHCCk (ORCPT ); Wed, 7 Nov 2018 21:02:40 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2CBDD3D3; Wed, 7 Nov 2018 16:31:35 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-55.bos.redhat.com [10.18.17.55]) by smtp.corp.redhat.com (Postfix) with ESMTP id 07DFE648DF; Wed, 7 Nov 2018 16:31:33 +0000 (UTC) Subject: Re: [PATCH] fs/proc: introduce /proc/stat2 file To: Davidlohr Bueso , Andrew Morton Cc: Daniel Colascione , linux-fsdevel@vger.kernel.org, linux-kernel , Davidlohr Bueso References: <20181029192521.23059-1-dave@stgolabs.net> <20181106154840.3b448356214afa63dc8cb28c@linux-foundation.org> <20181107033234.djng6kas4tjkevln@linux-r8p5> From: Waiman Long Openpgp: preference=signencrypt Autocrypt: addr=longman@redhat.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181107033234.djng6kas4tjkevln@linux-r8p5> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Wed, 07 Nov 2018 16:31:35 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/06/2018 10:32 PM, Davidlohr Bueso wrote: > On Tue, 06 Nov 2018, Andrew Morton wrote: > >> It would be interesting to know precisely which stat fields the >> database-which-shall-not-be-named is looking for.  Then we could cook >> up a very whizzy way of getting at the info. > > The ctxt field, afaik. In any case they have been able to work around > the bottleneck. I'm not sure if that is the case for Waiman, however. > In my case, the customers just complain about the slowdown in reading /proc/stat on some platforms vs. the others because some had many more interrupt lines than the others. They didn't specifically call out what they were looking at. >> >> A downside of the stat2 approach is that applications will need to be >> rebuilt.  And hopefully when people do this, they'll open >> "/etc/my-app-name/symlink-to-proc-stat" (or use per-application config) >> so they won't need a rebuild when we add /proc/stat3! >> >> A /proc/change-how-stat-works tunable would avoid the need to rebuild >> applications.  But if a system still has some applications which want >> the irq info then that doesn't work. >> >> It's all very sad, really. >> >> btw, >> >>> +The stat2 file acts as a performance alternative to /proc/stat for >>> workloads >>> +and systems that care and are under heavy irq load. In order to to >>> be completely >>> +compatible, /proc/stat and /proc/stat2 are identical with the >>> exception that the >>> +later will show 0 for any (hard)irq-related fields. This refers >>> particularly >> >> "latter" >> >>> +to the "intr" line and 'irq' column for that aggregate in the cpu >>> line. >> >> btw2, please quantify "poor performance".  That helps us determine how >> much we care about all of this! > > Up to a quarter of a second is what was reported as being spent every > time > /proc/stat is used. This is with 1k cores and 4k interrupts. > > Thanks, > Davidlohr Yes, the time spent will scale more or less linearly with the # of cores and # of interrupts. Thanks, Longman