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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, 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 B23B6C43387 for ; Fri, 18 Jan 2019 11:10:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7A3F72087E for ; Fri, 18 Jan 2019 11:10:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="c7Ovutsp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726761AbfARLKM (ORCPT ); Fri, 18 Jan 2019 06:10:12 -0500 Received: from mail-wr1-f66.google.com ([209.85.221.66]:33507 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725982AbfARLKL (ORCPT ); Fri, 18 Jan 2019 06:10:11 -0500 Received: by mail-wr1-f66.google.com with SMTP id c14so14605263wrr.0; Fri, 18 Jan 2019 03:10:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=i9Jz6mADl+SAlcH6gEeO3JwA6zj1h7g3kXeXLvf3Qh4=; b=c7OvutspFyLKMOanYTqFOhtdpU7ojaNNVvJVsg4XAm+1GYeuC7XX9Xu+fKTrDD6Huu HJQC3lrph0tk/EsV0XUd1Uf2YVoCFHoBspiiB6qOnYfiJisjF8hdIXAyPe5z0IHOoERf d+ZVQ0rTBjEHLZ350xYAXGHdc5PO3yHvLCpmBlgXIoF5PgovBkJrD0JFOG83e9eW/pQo 0UN0MNfCoR8n6vvDrnB2feSg8BPvSiNlewlZInoDo6eYsvbChrGuKDovg3aeWkKNVf2/ g7lCxkVgPp/ab1W9Eygu/cE19L/uL89L1PKjNyjA2ytquXYqi+lv1HgVlHIxy9u+eEsx nYZQ== 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=i9Jz6mADl+SAlcH6gEeO3JwA6zj1h7g3kXeXLvf3Qh4=; b=MlUOETbAVi3c5ofXvwmaWp0ofaMdGFBlB29/etjtZF3+pApi0gXtLY5RmzJTD2yXPr 7PjrVadXh3382dJLeCvV5YNrx1sdqLIvv/xSPrXqOlEHbkgedZ9ydA+u1S+jXas3le2u TONZhWp0bP5lQrxhSyFA0gmLVnRHaaWLX8PbRoXaLNmJlzmA+zuHOWD0QI4Eykh+CDGz KQs1gaHyUUoO3rtYmXlaK76OxC37I/Vm+uZhq1TB0A6PyUr5JCQ1SnT+ykvt/7IE1QAn EhNNMP2bAl7mHUYdJKqC4A0E0bMPFOjuBMXHCsK+Sxo4xtp7+Ay8mhXEqZF8VmaI14Lz cKTQ== X-Gm-Message-State: AJcUukdF/d56bvffC8HizOjy+FonSMjpkIBtLzk6T8USeBwZOuQ9jw53 DKPnklcpkYySGGLJddYL4g== X-Google-Smtp-Source: ALg8bN5HmuGWHZrf/Pe4lq0wPDcQ3aonXuxeHvlAvYBG6K6PrZDkNJ4+rKgm/Ot09izhnvbvSEmNsg== X-Received: by 2002:adf:dcd0:: with SMTP id x16mr15760897wrm.143.1547809809868; Fri, 18 Jan 2019 03:10:09 -0800 (PST) Received: from localhost (host89-130-dynamic.43-79-r.retail.telecomitalia.it. [79.43.130.89]) by smtp.gmail.com with ESMTPSA id o81sm69625423wmd.10.2019.01.18.03.10.09 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 18 Jan 2019 03:10:09 -0800 (PST) Date: Fri, 18 Jan 2019 12:10:08 +0100 From: Andrea Righi To: Paolo Valente Cc: Tejun Heo , Li Zefan , Johannes Weiner , Jens Axboe , Vivek Goyal , Josef Bacik , Dennis Zhou , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 0/3] cgroup: fsio throttle controller Message-ID: <20190118111008.GA25335@xps-13> References: <20190118103127.325-1-righi.andrea@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Fri, Jan 18, 2019 at 12:04:17PM +0100, Paolo Valente wrote: > > > > Il giorno 18 gen 2019, alle ore 11:31, Andrea Righi ha scritto: > > > > This is a redesign of my old cgroup-io-throttle controller: > > https://lwn.net/Articles/330531/ > > > > I'm resuming this old patch to point out a problem that I think is still > > not solved completely. > > > > = Problem = > > > > The io.max controller works really well at limiting synchronous I/O > > (READs), but a lot of I/O requests are initiated outside the context of > > the process that is ultimately responsible for its creation (e.g., > > WRITEs). > > > > Throttling at the block layer in some cases is too late and we may end > > up slowing down processes that are not responsible for the I/O that > > is being processed at that level. > > > > = Proposed solution = > > > > The main idea of this controller is to split I/O measurement and I/O > > throttling: I/O is measured at the block layer for READS, at page cache > > (dirty pages) for WRITEs, and processes are limited while they're > > generating I/O at the VFS level, based on the measured I/O. > > > > Hi Andrea, > what the about the case where two processes are dirtying the same > pages? Which will be charged? > > Thanks, > Paolo Hi Paolo, in this case only the first one will be charged for the I/O activity (the one that changes a page from clean to dirty). This is probably not totally fair in some cases, but I think it's a good compromise, at the end rewriting the same page over and over while it's already dirty doesn't actually generate I/O activity, until the page is flushed back to disk. Obviously I'm open to other better ideas and suggestions. Thanks! -Andrea