From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on gnuweeb.org X-Spam-Level: X-Spam-Status: No, score=-0.0 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, RCVD_IN_DNSWL_NONE,SPF_HELO_PASS,SPF_SOFTFAIL autolearn=ham autolearn_force=no version=3.4.6 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4E12C433EF for ; Wed, 9 Mar 2022 23:43:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230371AbiCIXoT (ORCPT ); Wed, 9 Mar 2022 18:44:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40400 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229680AbiCIXoS (ORCPT ); Wed, 9 Mar 2022 18:44:18 -0500 Received: from mail-pg1-x52a.google.com (mail-pg1-x52a.google.com [IPv6:2607:f8b0:4864:20::52a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B39A6C7D5E for ; Wed, 9 Mar 2022 15:43:17 -0800 (PST) Received: by mail-pg1-x52a.google.com with SMTP id bc27so3258694pgb.4 for ; Wed, 09 Mar 2022 15:43:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=Yh83gLKF0p1HHh6qhQqRKF6fIAAp3Y2uQvxaiLyuPsU=; b=xoNdTgj6Ln1Fby9YRHf9Xc9g24AUqIN6pmO1h5HBqRS9ulU7ojjZYPkKArHCMfPiJN sLNBnWD6YYNrisE38OEqgb5UEAnBLGj0yXzUlkYCwBlxeGa8UL7hDBf6sL70YuWcyfbd 3Q5ITx3tG/aIO6lNJMpXkB9lRHAMUR2l1eal5nMm7kJEpp2/TwZHM/whmAhP4P/MJE4i gHOhUndGPjMgyBJH3CQ2q54zvhhiTP4+JquA8FbQXpsXTntZykXiCW8Z8xr4YClA7QuM mEPF8g3jmgvDVnwkoy8cI4FIv2Vxr3jnC0ZMj1d/w5V9lbP/4jPSG4LDdBpy4W0ZvkI5 zMNw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=Yh83gLKF0p1HHh6qhQqRKF6fIAAp3Y2uQvxaiLyuPsU=; b=Jty+cUJmZjIfuaKNCfaGgmHwDgM34KN3WDmgNcmQXYYLYEyQTKCOxW5njDw1lXBjH/ iTBCcIDsPIfl8y7+GaRXwLxGAPR610nFomze+VsBq3kDFqdpjPdW8tZKUWqZfydz8szZ L4DADb8b2AKMq9RXBnEMuIQS6mB5xfRS6HWPYUO5Mk1IvpkN9xKkR1P/5KE3/J8NrBBe fp2o1lo4tvsUrIxdjZuWFGz8pVZxt3zqeb520DuT1pMwiiGaonY1qSfdE4YXANIScIIA ITWDl2fnaJP5mbComJkjwVx439FbX8Y4g2qn460hheNaVltOl2/e1USnW5tgEKFJ3aQM /tbQ== X-Gm-Message-State: AOAM533+j3+X/HvlIcNx9AaZVSK7JThfvRRR7zppVlaEEUxctUxzTBqi +iLMeRF/YHoRzIybi4xx0ni7ucBDh/ItNBqN X-Google-Smtp-Source: ABdhPJxtyuiApdlC6vCUDN2zD1v9b70l5hGiGyrK89jPnH8X3n1cNInXybB9F7RbawZlAYomV3L+NA== X-Received: by 2002:a63:6b42:0:b0:37c:4e5c:a903 with SMTP id g63-20020a636b42000000b0037c4e5ca903mr1683809pgc.463.1646869397195; Wed, 09 Mar 2022 15:43:17 -0800 (PST) Received: from [192.168.1.100] ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id k6-20020a056a00134600b004f755f386d8sm4100146pfu.87.2022.03.09.15.43.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Mar 2022 15:43:16 -0800 (PST) Message-ID: Date: Wed, 9 Mar 2022 16:43:15 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH v5 1/2] io_uring: minor io_cqring_wait() optimization Content-Language: en-US To: Olivier Langlois , Pavel Begunkov Cc: Hao Xu , io-uring , linux-kernel References: <84513f7cc1b1fb31d8f4cb910aee033391d036b4.1646777484.git.olivier@trillion01.com> <7f39095c-1070-7a70-91a0-b0ccb33c368b@kernel.dk> <36cd0f716bda419f477c3256769f382a31461481.camel@trillion01.com> From: Jens Axboe In-Reply-To: <36cd0f716bda419f477c3256769f382a31461481.camel@trillion01.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 3/8/22 10:36 PM, Olivier Langlois wrote: > On Tue, 2022-03-08 at 17:54 -0700, Jens Axboe wrote: >> On 3/8/22 3:17 PM, Olivier Langlois wrote: >>> Move up the block manipulating the sig variable to execute code >>> that may encounter an error and exit first before continuing >>> executing the rest of the function and avoid useless computations >> >> I don't think this is worthwhile doing. If you're hitting an error >> in any of them, it's by definition not the fast path. >> > Well, by itself it is not a big improvement but it is still an > improvement. > > but most importantly, it has to be considered in the context of the > current patchset because in patch #2, the following step is to > > 1. acquire the napi spin lock > 2. splice the context napi list into a local one. > 3. release the lock > > If this patch is not in place before patch #2, you would need undo all > that before returning from the sig block which would make the function > bigger when all that is completely avoidable by accepting this patch... > > Both patches were together in v1 but I decided to break them apart > thinking that this was the right thing to do... Yeah ok, it does make sense in the context of patch 2. Thanks! -- Jens Axboe