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=-2.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_MED, USER_AGENT_MUTT 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 F0D25C46470 for ; Tue, 7 Aug 2018 17:48:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AB090205C9 for ; Tue, 7 Aug 2018 17:48:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cmpxchg-org.20150623.gappssmtp.com header.i=@cmpxchg-org.20150623.gappssmtp.com header.b="xUf/RW9P" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AB090205C9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=cmpxchg.org 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 S2403861AbeHGUEB (ORCPT ); Tue, 7 Aug 2018 16:04:01 -0400 Received: from mail-yw1-f68.google.com ([209.85.161.68]:39619 "EHLO mail-yw1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389098AbeHGUEA (ORCPT ); Tue, 7 Aug 2018 16:04:00 -0400 Received: by mail-yw1-f68.google.com with SMTP id r184-v6so5255528ywg.6 for ; Tue, 07 Aug 2018 10:48:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=UpJ6FyGDkvX9DB3o64kenGl56IYvhdWQ2odl8ODKXXc=; b=xUf/RW9PAuGdg/aPmdXZd061y1b6q1zGr+kLQpDEaAEzJooB6827zXKVhjRHGN5n7e HIjUtKUyaJOXzgZuXxznZcNUilT1xBZhA5aehh8lQruhFsIUm8GVYWMTmkLoG2UTPfFs vXqQAH1vMLhucdZdSZ4omgtizpiFeVV32ipqPL4lUmkAsZCnWsRzwoCDnvuNz8bWCYbl uCU6edKUuslSG6p9dY6Byjne8s33D9qm4zN4uqiFICsUB7jHC5eo+Wh79SWpC+5PHWUD RNbqEMybZilTZhuktqRbxx2meHfWOn6J2tgPU9iNxja8HbkPqNkIuvqHrNMH4w4IZupg IS3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=UpJ6FyGDkvX9DB3o64kenGl56IYvhdWQ2odl8ODKXXc=; b=fGQXOnIZAYNJqR2K4MXXiBI1a6pVUNt8udMIBSJMSXOB/Sb0hHB9bLbfiyFhVCMd1+ YAg0YROrwIqiM0HwaMyCcKh8GAQuGbG47+urgiOTVoP7pyGJN1m5w2UIFd1HgKnmXYpx Zf+H+a3Dn5jETfTJTMAr/fPzBOILCumUSSoyC4w/2bZEAs22QaXiZUHujg2W6cuoQkOu XrF4L+GQovTgrYIu9URlcuQAdgX0F48Lbp5qF9INLje0oisr2vPTs3YaXtBlwwq9I7BY 0nc2Z8gkYFHpfzuqSxHa8kjNFE+PiWKhoXD0o1+44mNqkbtfeF829oxgFy4Yqai4pvhK M+5A== X-Gm-Message-State: AOUpUlF8xK1CHYsIgucms8SH5kLUWUkVaaJWXsrdFgtu8X/AqeYmZ3xY 8Wm34/65uVPfdh3afXzaGXFoZA== X-Google-Smtp-Source: AAOMgpfyGRDHr22y+5Nd13+1Rpwl+ewoJzO0ff09ocAZogHy94T/qzN7rFFL6n9747hyF5drVzDpdg== X-Received: by 2002:a81:430f:: with SMTP id q15-v6mr10431320ywa.39.1533664114079; Tue, 07 Aug 2018 10:48:34 -0700 (PDT) Received: from localhost ([2620:10d:c091:180::1:2058]) by smtp.gmail.com with ESMTPSA id 139-v6sm801985ywr.61.2018.08.07.10.48.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 07 Aug 2018 10:48:32 -0700 (PDT) Date: Tue, 7 Aug 2018 13:51:32 -0400 From: Johannes Weiner To: peter enderborg Cc: Ingo Molnar , Peter Zijlstra , Andrew Morton , Linus Torvalds , Tejun Heo , Suren Baghdasaryan , Daniel Drake , Vinayak Menon , Christopher Lameter , Mike Galbraith , Shakeel Butt , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 0/9] psi: pressure stall information for CPU, memory, and IO v3 Message-ID: <20180807175132.GA27979@cmpxchg.org> References: <20180801151958.32590-1-hannes@cmpxchg.org> <5576a988-fca9-15a5-5fa8-16f704ea20fb@sony.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5576a988-fca9-15a5-5fa8-16f704ea20fb@sony.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 07, 2018 at 01:50:09PM +0200, peter enderborg wrote: > On 08/01/2018 05:19 PM, Johannes Weiner wrote: > > > > A kernel with CONFIG_PSI=y will create a /proc/pressure directory with > > 3 files: cpu, memory, and io. If using cgroup2, cgroups will also have > > cpu.pressure, memory.pressure and io.pressure files, which simply > > aggregate task stalls at the cgroup level instead of system-wide. > > > Usually there are objections to add more stuff to /proc. Is this an exception? It seems like a good fit given that all other system stats of this type and format are there: loadavg, schedstat, diskstats, uptime etc. sysfs, and its concept of kernel objects and their attributes, doesn't really match the type of info exported here. And its breakdown of complex information into many directories and files can be kind of tedious to be honest; some information is just more human readable in a simple table, and still trivial to parse mechanically. It would also be nice to keep the same file format for both the system level and cgroups, to avoid having two separate presentations (and two parsers) for the same type of information at different scopes, but the sysfs design goals clash with the cgroupfs ones. If we exported the system stats at the root cgroup level, we'd still need an interface for !CGROUP systems, and having two ways of reading actually identical data would again be fairly ugly.