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=-2.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 4ED67C432C0 for ; Thu, 21 Nov 2019 13:47:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20DCF2070A for ; Thu, 21 Nov 2019 13:47:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="JiXoNspg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726869AbfKUNrU (ORCPT ); Thu, 21 Nov 2019 08:47:20 -0500 Received: from mail-pg1-f196.google.com ([209.85.215.196]:42918 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726358AbfKUNrT (ORCPT ); Thu, 21 Nov 2019 08:47:19 -0500 Received: by mail-pg1-f196.google.com with SMTP id q17so1613124pgt.9 for ; Thu, 21 Nov 2019 05:47:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=MyAiivcsF2PofDHmK8dKWR/6pmgyuHLP/0IXYbVSHUI=; b=JiXoNspg/7NCEu0esQ7xr9DOl2sx1niS8rRCX2AcTXH17rrG8iYmM/ZRu9CAY8ZYMl TkOXqm4nxG7Zl06Wj/NxsqQtW/uZgC/ZTdRYyg4JLr+2FZ5fg0liEFyK8F1Rm0nSL24F Ikaqs0YXTuUyiDcohFnS1PYgxrFRbEU8Bud52mk3ybjPWpyUMgF4DZ0EnJZ6m8/GzZjA yMCYpL9cIVq4PeyEMtJxHGgE67YbpEqGC7n9awaqA7tjlqn8Ss5OwYmq4uxVHMRaNf40 QPhpJXdC1VlOVCmIdD8V9HHt6eIAXfknwWAERFYCZW4W/YQN5mtDXCbKXRgH40O4OlIK JtBQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=MyAiivcsF2PofDHmK8dKWR/6pmgyuHLP/0IXYbVSHUI=; b=GzAFNtbMt9nIm+TYybLw3N7xlIVDBRBpFyXoFcWm28I0Zv811sFRDIbvzDj9m1NPy9 KLjjrWqFHc7HKc21dORTggCbduuFi3GxL5AjxMm/m7bYX6hX8INLBK8ZcQpS2pby+eMo mvktAs7+aqybD3ut69I05C5YulaJSQiPVJbQ76vTVf3efgXqkncXs6jw8aFi6G/T4mVt ETi116x8rX37mv1ISFWTC7VZsvUCboFXyyH4p8bMqo6IbySRIpNdT3YVBsNktac2p+Mn VZDQHSP3+jiMpq7xeCZVojnCvzt+3aFLDHauJqSvd647hicsV8aUeq3w7H8RE/3nkkxK 59eA== X-Gm-Message-State: APjAAAV49yhmhWUfp2IxzsotAkkjtWyZJVvDD5SI8Jmq3la97b+Re/c/ /8Rn7Ez5E/mMiS23F40br5TkiZSy7+/Wig== X-Google-Smtp-Source: APXvYqwbn41c/brPs4x2Tq13lwX2yzOcY+e0MWa+oyQDjiDCmdOHkQnfzJGRLf8Cnoshtd6seDy0qg== X-Received: by 2002:a63:d258:: with SMTP id t24mr9604702pgi.289.1574344038367; Thu, 21 Nov 2019 05:47:18 -0800 (PST) Received: from [192.168.1.188] ([66.219.217.79]) by smtp.gmail.com with ESMTPSA id u3sm3468901pjn.0.2019.11.21.05.47.16 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 21 Nov 2019 05:47:17 -0800 (PST) Subject: Re: [PATCH] io_uring: drain next sqe instead of shadowing To: Jackie Liu , Pavel Begunkov Cc: io-uring@vger.kernel.org References: <2005c339-5ed3-6c2e-f011-5bc89dac3f5c@kernel.dk> <5e8a8176e29a61ec79004521bc2ef28e4d9715b1.1574325863.git.asml.silence@gmail.com> <5dd68282.1c69fb81.110a.43a7SMTPIN_ADDED_BROKEN@mx.google.com> <6da3585e-b419-ea9b-4246-1ee5ca14f5b9@gmail.com> <5dd68820.1c69fb81.64e0b.4340SMTPIN_ADDED_BROKEN@mx.google.com> From: Jens Axboe Message-ID: Date: Thu, 21 Nov 2019 06:47:15 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <5dd68820.1c69fb81.64e0b.4340SMTPIN_ADDED_BROKEN@mx.google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 11/21/19 5:49 AM, Jackie Liu wrote: > > > On 2019/11/21 20:40, Pavel Begunkov wrote: >>> 在 2019/11/21 17:43, Pavel Begunkov 写道: >>>> On 11/21/2019 12:26 PM, Jackie Liu wrote: >>>>> 2019年11月21日 16:54，Pavel Begunkov 写道： >>>>>> >>>>>> If there is a DRAIN in the middle of a link, it uses shadow req. Defer >>>>>> the next request/link instead. This: >>>>>> >>>>>> Pros: >>>>>> 1. removes semi-duplicated code >>>>>> 2. doesn't allocate memory for shadows >>>>>> 3. works better if only the head marked for drain >>>>> >>>>> I thought about this before, just only drain the head, but if the >>>>> latter IO depends >>>>> on the link-list, then latter IO will run in front of the link-list. >>>>> If we think it >>>>> is acceptable, then I think it is ok for me. >>>> >>>> If I got your point right, latter requests won't run ahead of the >>>> link-list. There shouldn't be change of behaviour. >>>> >>>> The purpose of shadow requests is to mark some request right ahead of >>>> the link for draining. This patch uses not a specially added shadow >>>> request, but the following regular one. And, as drained IO shouldn't be >>>> issued until every request behind completed, this should give the same >>>> effect. >>>> >>>> Am I missed something? >>> >>> Thanks for explaining. This is also correct, if I understand >>> correctly, It seems that other IOs will wait for all the links are >>> done. this is a little different, is it? >> >> Yes, you're right, it also was briefly stated in the patch description >> (see Cons). I hope, links + drain in the middle is an uncommon case. >> But it can be added back, but may become a little bit uglier. >> >> What do you think, should we care about this case? > > Yes, this is a very tiny scene. When I first time wrote this part of the > code, my suggestion was to ban it directly. > > For this patch, I am fine, Jens, what do you think. I am fine with it as well, it'd be nice to get rid of needing that extra request. Was that a reviewed-by from you? It'd be nice to get these more formally so I can add the attributes. I'll drop the other patch. > The mailing list always rejects my mail, is my smtp server IP banned? Probably because you have text/html in your email, the list is pretty picky when it comes to anything that isn't just text/plain. -- Jens Axboe