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 E435DC432C3 for ; Thu, 21 Nov 2019 15:12:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B8DA9206F4 for ; Thu, 21 Nov 2019 15:12:49 +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="kPjbYopq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726563AbfKUPMt (ORCPT ); Thu, 21 Nov 2019 10:12:49 -0500 Received: from mail-io1-f48.google.com ([209.85.166.48]:43728 "EHLO mail-io1-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726676AbfKUPMt (ORCPT ); Thu, 21 Nov 2019 10:12:49 -0500 Received: by mail-io1-f48.google.com with SMTP id r2so3768828iot.10 for ; Thu, 21 Nov 2019 07:12:48 -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=FKmA1dj5ul8c9B7/AW1SeCE2cpRR3rxrM0o5i/Y/WKw=; b=kPjbYopquByXxCpTTv4yW6ae0DzuMCCGFTqwC83zxvmsyx8WrHMiEdgOaJr24m5K0Z AG/KSf0wjRpe06+EIKYX2SPxBwqicHeWqeiOBBACFSN1+adFlpUm4zfDob5aAruGwTkh HDamk9xy8JroO5Sahk4I5I651OaxVlxlpNBbbuRvuTgdav+K3kYZwKop/a7K/MC4jk18 c5yI1apmxjtDvfiBxRiS19n80FR/n/azXeb6PH/PGgDJ3ByG0YZLiMmarajeJVfyuTya DPXCMxV0EQ62vBolL6QxQGuoz6Sy/ulpVal1Y/uRSdMGxt8aDRIs/fweW2Tz9OFu2/IQ eYdw== 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=FKmA1dj5ul8c9B7/AW1SeCE2cpRR3rxrM0o5i/Y/WKw=; b=RyBCdmiutUC7VxKimkw2GTyfgkrcxueTIotR21LomM7yRtqGIc6GfiQc9/TywxNBAS lCb2mtS2wA4S8SW5B2J6wHEGSaMmP1fxpgR+uGZ8dZWsafBWVhnStg6uD8GxWNCLk4mI VpXC4gYBluXWWlsDrDWqsD76mKG393Be7sPqON/S4fyR3eXMT0Gnl+H4hHnjo5gqId3L 6QewNvVabI1k0sKV5BPqQKT6zY40v8eEVziwdpLUVUeQIBIX9lgfDz968PtfZaYjTA0W 82tRbJ3h7+DdauEIfygKRK8DuLrGBoJHqA0iO4QQ/V5MvOmGehcrFoxCDhx6syECxObT AQLg== X-Gm-Message-State: APjAAAVQVjtOzFrnRsQLoY3HGAXKbzubVCDzEPBgR27tVVbxuJg6gQfy 5tz9waD/R47gePiGQV+nBqskE8icaFzFaA== X-Google-Smtp-Source: APXvYqxEdS90T8xK24DILdvLmLtAXt1mypIl4z907MN6f4VHjxfG7Uo1byqt/5792BYm3irrfWg9Cg== X-Received: by 2002:a5d:8555:: with SMTP id b21mr8346818ios.22.1574349167334; Thu, 21 Nov 2019 07:12:47 -0800 (PST) Received: from [192.168.1.159] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id r18sm1264449ilq.75.2019.11.21.07.12.46 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 21 Nov 2019 07:12:46 -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> <5dd69c7f.1c69fb81.8868.e3c2SMTPIN_ADDED_BROKEN@mx.google.com> From: Jens Axboe Message-ID: <4b90e56e-1190-eeb5-f61a-c8d3a0f2d969@kernel.dk> Date: Thu, 21 Nov 2019 06:54:44 -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: <5dd69c7f.1c69fb81.8868.e3c2SMTPIN_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 7:16 AM, Jackie Liu wrote: > 在 2019/11/21 21:47, Jens Axboe 写道: >> 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. > > I want to do more tests. There is no test machine at this time, at least > until tomorrow morning. OK, no worries, for the record I did run it through testing this morning and it passes for me. Before this (or my) patch, we'd stall pretty quickly in the link_drain tested if run repeatedly. >>> 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. > > I don't know, I use thunderbird to write emails, and it has been set to > plain text, perhaps because of the signature, I have to check my mail > client. Feel free to try and send an email to me personally, then I can see what it looks like. -- Jens Axboe