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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DDB43ECAAD8 for ; Fri, 23 Sep 2022 14:34:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232123AbiIWOeb (ORCPT ); Fri, 23 Sep 2022 10:34:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48816 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232165AbiIWOe0 (ORCPT ); Fri, 23 Sep 2022 10:34:26 -0400 Received: from mail-io1-xd2c.google.com (mail-io1-xd2c.google.com [IPv6:2607:f8b0:4864:20::d2c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7A1401438E9 for ; Fri, 23 Sep 2022 07:34:16 -0700 (PDT) Received: by mail-io1-xd2c.google.com with SMTP id v128so26334ioe.12 for ; Fri, 23 Sep 2022 07:34:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date; bh=nxzsu1M19YT2nyIAMz4gLe554jfsOXqZNJWh0ehS8Gw=; b=NUUyDTkgR1lJ/k3CZaVQP0eENyhRVUV3GCTDufEr+fPV6EFeBEEKCnCOoQFRfah4jU V4sxRpoirv5DnAbMkC771Hwx0wXUFdQROjcmHMzYYgiDhhGFgILv5iA1YcXBHdp8+LMd JTIY77EcQqNTmkh6BXDtkhtobryTSdRuQYxY1QzINbCv0pTOMQEEUoP9ytCJpbkUbkVQ +ml3xSdAbC+2a1xAEJboIkctR6hJvc/57QP0ltHsRlyZ72oZ7K2sXBtmKgfhV4QNBgMA VJAPyTCGffXS/EId52DwbdUKU2Q29fNtIRMcX07HRS2drgd+HaGleT78jgsTF28NasD+ JAWA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date; bh=nxzsu1M19YT2nyIAMz4gLe554jfsOXqZNJWh0ehS8Gw=; b=WJBNg3HMkgl5BtxoAb/Arwh1Dxv3B+iG6h5bzG4DsSGbYZsn6Dd7IqfI+/6t3TceQo HWX4cmzcbM89Ez6yNTmQ2OSsDGDwqWZGZ5Ve402io55JQgN6DXZXbX8q//roHkaDN9hg DoKCY7BuV2iLiNvwSb55p7DkeeGPZ3ok0Efw0+l3gBOCPhOj4ohZHa8Nt9aXTTjYcXXA J7wj/qYU2ipl3b56aUub1pK2q75tclvFAUcIGFX56N0Luf15+h1dg/8Osf+6cg3MUZi+ 2RdClHhc+CpT/WzkHTDXr0RPy+uPHKnUdBc4XghKRb4TpAMJzA5gUC4tHldEeoUp2zlp XF0g== X-Gm-Message-State: ACrzQf2ydsdhpV3igiCxBeEZqS2g/jsy5QOS99ZqKCgMobin7yAAiDUp IHHVEKbju/3VuWwogXwD8lxttg== X-Google-Smtp-Source: AMsMyM7m3cfqgdxA99SG5awcx7XVjPRG5NSyJJvk14/Ft1gw6jypDMsyw+8wjxAx8f3mGRK2WIQ+Lg== X-Received: by 2002:a5e:840e:0:b0:69f:c4e:15c4 with SMTP id h14-20020a5e840e000000b0069f0c4e15c4mr4046191ioj.1.1663943655457; Fri, 23 Sep 2022 07:34:15 -0700 (PDT) Received: from [192.168.1.94] ([207.135.234.126]) by smtp.gmail.com with ESMTPSA id q24-20020a02b058000000b003566d1abeabsm3424165jah.5.2022.09.23.07.34.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 23 Sep 2022 07:34:14 -0700 (PDT) Message-ID: Date: Fri, 23 Sep 2022 08:34:11 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [PATCH for-next] io_uring: fix CQE reordering Content-Language: en-US To: Dylan Yudaken , "asml.silence@gmail.com" , "io-uring@vger.kernel.org" References: <2815cf233c3171204823eda9a18f7c67894b7db9.camel@fb.com> From: Jens Axboe In-Reply-To: <2815cf233c3171204823eda9a18f7c67894b7db9.camel@fb.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 9/23/22 8:32 AM, Dylan Yudaken wrote: > On Fri, 2022-09-23 at 14:53 +0100, Pavel Begunkov wrote: >> Overflowing CQEs may result in reordeing, which is buggy in case of >> links, F_MORE and so. >> > > Maybe the commit message got cut off? > > > I think this is probably ok, the downside being that CQE's with no > ordering constraints will have ordering forced on them. An alternative > would be for each case (eg linked, zerocopy, multishot) to either pause > or force CQE's to be overflow ones. This wouldnt slow down the other > codepaths. I don't have an idea for how difficult this might be. I don't think this matters at all. If you hit overflow, things are screwed and slow anyway. Doesn't make sense to optimize for that path, so we may as well impose ordering for everything at that point. -- Jens Axboe