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=-8.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 75F52C43215 for ; Fri, 29 Nov 2019 09:45:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4A64E21774 for ; Fri, 29 Nov 2019 09:45:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="LnYAyqGk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726810AbfK2JpK (ORCPT ); Fri, 29 Nov 2019 04:45:10 -0500 Received: from mail-lj1-f195.google.com ([209.85.208.195]:39297 "EHLO mail-lj1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725892AbfK2JpJ (ORCPT ); Fri, 29 Nov 2019 04:45:09 -0500 Received: by mail-lj1-f195.google.com with SMTP id e10so22102189ljj.6; Fri, 29 Nov 2019 01:45:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=h89gtr4jirvEqw+istiKuMh6C9n8rYoQsr7cxtnxOQE=; b=LnYAyqGkTPjTtDnkPptBD1c4uizp/XqM/K+oUqJfRVRvqwY8q/C/9JZO1kF9M8Z0/N RgWQXJpX8RkBSnd0oYsTulp32+lThwE1+rbZLZtrNUvmPu+2EZP3pzabBEZerXaahB6M /BoEPVa51+oEJyu4iI1LzRnm1t+iroic76VbNEMti7ji8C37RpxO6JcZoPiacMrsD03a reL8QPnD9yco+0MPd8GHwS03TtDVxsgsLz4QtJ+xwYTIG2FqnxkAOyrxhtcq54f3Me2Z 5To/FtbgbjkVmu1DFyZtiqJbu/yU9MFuA8yEuw2iR65JxMoLmkOWdWBnBaiJmgcsYxYU fPmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=h89gtr4jirvEqw+istiKuMh6C9n8rYoQsr7cxtnxOQE=; b=a8Kgj7gJVr8Hyebl9ac/wvabT2nymfloZL3M8XDBa39zEenMd/9t05+NMedsLQtC5b JkEzNlvPrskgVAwOPsMssMChoynV5TNQCICegx/jD82txTLeC05NFn6JGAIHKNHS5Ajo Z/7nIQ5a0G5kk0y6kCQiYG+d8FmhLsF96EdanGcUMpBdKUScDpYuFyBDZODgZlePWRQk OeYdxkS3RRRzPQvPoXebTePEQiu3M0oAxhH97qc0ENF9dcDZhLL8fIeeFqIMqFqAC/Ak aVXlVSxwxtbmZ9UgqCN7xXnZPBxiyP8Dmg7Rb6rrU53/ZSLSmDCT1M62RCZ0nt5XJonw 0Jqg== X-Gm-Message-State: APjAAAXtwrmdjwERMQET6PSeD2MJrWTgVSoMfgT6OMRjKtGg/k/pfMqh A+zGBK1rAN4AnHZ6mcX5T8yZsn+nUTw= X-Google-Smtp-Source: APXvYqymHjqtZ5yLRtHmfHQHjzkdwaZzbuI/7qkmGsPIBQkf4vtO2fa7lH85D+4iKu06z/+F/yXJ/g== X-Received: by 2002:a2e:3313:: with SMTP id d19mr38009377ljc.240.1575020705682; Fri, 29 Nov 2019 01:45:05 -0800 (PST) Received: from [172.31.190.83] ([86.57.146.226]) by smtp.gmail.com with ESMTPSA id a24sm547142ljp.97.2019.11.29.01.45.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 29 Nov 2019 01:45:04 -0800 (PST) Subject: Re: [PATCH 1/3] blk-mq: optimise rq sort function To: Nikolay Borisov , Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <0124910c-4dcf-2143-0ec6-32dad123067c@suse.com> From: Pavel Begunkov Message-ID: <7b1a16db-287f-bba0-fca0-cc7f85f69ec6@gmail.com> Date: Fri, 29 Nov 2019 12:45:03 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <0124910c-4dcf-2143-0ec6-32dad123067c@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/29/2019 11:28 AM, Nikolay Borisov wrote: > On 28.11.19 г. 23:11 ч., Pavel Begunkov wrote: >> Check "!=" in multi-layer comparisons. The same memory usage, fewer >> instructions, and 2 from 4 jumps are replaced with SETcc. >> >> Note, that list_sort() doesn't differ 0 and <0. >> >> Signed-off-by: Pavel Begunkov > > My first reaction was this is wrong since you no longer return negative > values. But then I looked into list_sort/merge and this branch > 'if (cmp(priv, a, b) <= 0) {' clearly shows this is correct. Yes, that's why there is a note in the patch description. The same is told by list_sort() description. > > So : > > Reviewed-by: Nikolay Borisov Thanks for taking a look > >> --- >> block/blk-mq.c | 12 ++++-------- >> 1 file changed, 4 insertions(+), 8 deletions(-) >> >> diff --git a/block/blk-mq.c b/block/blk-mq.c >> index 323c9cb28066..f32a3cfdd34e 100644 >> --- a/block/blk-mq.c >> +++ b/block/blk-mq.c >> @@ -1668,14 +1668,10 @@ static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b) >> struct request *rqa = container_of(a, struct request, queuelist); >> struct request *rqb = container_of(b, struct request, queuelist); >> >> - if (rqa->mq_ctx < rqb->mq_ctx) >> - return -1; >> - else if (rqa->mq_ctx > rqb->mq_ctx) >> - return 1; >> - else if (rqa->mq_hctx < rqb->mq_hctx) >> - return -1; >> - else if (rqa->mq_hctx > rqb->mq_hctx) >> - return 1; >> + if (rqa->mq_ctx != rqb->mq_ctx) >> + return rqa->mq_ctx > rqb->mq_ctx; >> + if (rqa->mq_hctx != rqb->mq_hctx) >> + return rqa->mq_hctx > rqb->mq_hctx; >> >> return blk_rq_pos(rqa) > blk_rq_pos(rqb); >> } >> -- Pavel Begunkov