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=-14.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 CA63CC433DB for ; Thu, 28 Jan 2021 12:32:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8360164DDD for ; Thu, 28 Jan 2021 12:32:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229595AbhA1McI (ORCPT ); Thu, 28 Jan 2021 07:32:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229594AbhA1McF (ORCPT ); Thu, 28 Jan 2021 07:32:05 -0500 Received: from mail-wr1-x430.google.com (mail-wr1-x430.google.com [IPv6:2a00:1450:4864:20::430]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D747C061573 for ; Thu, 28 Jan 2021 04:31:22 -0800 (PST) Received: by mail-wr1-x430.google.com with SMTP id g10so5228517wrx.1 for ; Thu, 28 Jan 2021 04:31:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=to:cc:references:from:autocrypt:subject:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=eLMbLXUCuNwOJVUowoThDWNV0gGCcGhCJIGXONM8jQo=; b=aKWrF6pqETFS17OpD0t1Ct1RUiRnBC6DdObt3Cmwcz9lIPcSF8wVSKKiadIs/uIShW z+MSqJJsxVPfSHQF+z2RzZ3Wz1iRbbzldPalZpq0dZBYlwqf04tRgC5YAzqjb9BKnv59 KbrkEI9qclW+EV2nvY/Vk+7FiX+yqVbBuY1OHxSucysZad+ySdL4trRNywaV0/EekZ7D +GXksDwjy7g+8p48K5QjwGfkeo3suA+4LFhK5PgDn1bfPFVVNelxPiiHaxElNUSxR7J/ N2CvG9ecptkipisvQQoW+8myuxTnlfDew3RzvnaSi02J8l6OLN3ZVTTDet0kxid51ec1 BiQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:cc:references:from:autocrypt:subject :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=eLMbLXUCuNwOJVUowoThDWNV0gGCcGhCJIGXONM8jQo=; b=YtJbKFywn7LHJOaLRxPcuIWY4MqVSoVvCfO7rk11DoCAXc1rTCslEJ6ysYOluVvhfP eQJzaeIMPSH7awq7GGCGdBADYVGPbXhxi5z2PY2efvvOPAm1zQoPI0s3flCr2Dsulz29 iCTKzkynw3TMxT9kJmHTny9JbBZnQOg5DA/kcCznSwpX5Wkb9ceVRJQcUERJnTh/HA+A C0tpPqEqaaK8mNrU6RndTaz4frOHnbhMICSGychSjInbVp1VZFB9bsUC2+xEj6o903Ci EH10deQq9jsK41RKfyXU07WNrfPwxIHHqOhmG8yDzT02R6TvsPtNnHa5AXCGmKbtQPi1 mI6g== X-Gm-Message-State: AOAM531tzHG5uLKGBseAD5giNmFpa6UNxtvEtjI3y/yBSKQjCFRfOTTF 5nDm0qXPh7CSs5tQnva+jLY= X-Google-Smtp-Source: ABdhPJx96xkos4KUHC9pX4Bj9kZfJpwkuTr/Zbn3FKIQNEOs9Rh0UCw4+yPdALvh5kDkj+PCSygF3g== X-Received: by 2002:a5d:4806:: with SMTP id l6mr16360054wrq.389.1611837081232; Thu, 28 Jan 2021 04:31:21 -0800 (PST) Received: from [192.168.8.160] ([148.252.132.131]) by smtp.gmail.com with ESMTPSA id g14sm7446588wru.45.2021.01.28.04.31.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 28 Jan 2021 04:31:20 -0800 (PST) To: Ming Lei Cc: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig References: <53b86d4e86c4913658cb0f472dcc3e22ef75396b.1609875589.git.asml.silence@gmail.com> <20210128121035.GA1495297@T590> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Subject: Re: [RFC 2/2] block: add a fast path for seg split of large bio Message-ID: <48e8c791-fe4a-60c7-aa8b-bcaf0f5562c9@gmail.com> Date: Thu, 28 Jan 2021 12:27:39 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <20210128121035.GA1495297@T590> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 28/01/2021 12:10, Ming Lei wrote: > On Tue, Jan 05, 2021 at 07:43:38PM +0000, Pavel Begunkov wrote: >> blk_bio_segment_split() is very heavy, but the current fast path covers >> only one-segment under PAGE_SIZE bios. Add another one by estimating an >> upper bound of sectors a bio can contain. >> >> One restricting factor here is queue_max_segment_size(), which it >> compare against full iter size to not dig into bvecs. By default it's >> 64KB, and so for requests under 64KB, but for those falling under the >> conditions it's much faster. >> >> Signed-off-by: Pavel Begunkov >> --- >> block/blk-merge.c | 29 +++++++++++++++++++++++++---- >> 1 file changed, 25 insertions(+), 4 deletions(-) >> >> diff --git a/block/blk-merge.c b/block/blk-merge.c >> index 84b9635b5d57..15d75f3ffc30 100644 >> --- a/block/blk-merge.c >> +++ b/block/blk-merge.c >> @@ -226,12 +226,12 @@ static bool bvec_split_segs(const struct request_queue *q, >> static struct bio *__blk_bio_segment_split(struct request_queue *q, >> struct bio *bio, >> struct bio_set *bs, >> - unsigned *segs) >> + unsigned *segs, >> + const unsigned max_sectors) >> { >> struct bio_vec bv, bvprv, *bvprvp = NULL; >> struct bvec_iter iter; >> unsigned nsegs = 0, sectors = 0; >> - const unsigned max_sectors = get_max_io_size(q, bio); >> const unsigned max_segs = queue_max_segments(q); >> >> bio_for_each_bvec(bv, bio, iter) { >> @@ -295,6 +295,9 @@ static inline struct bio *blk_bio_segment_split(struct request_queue *q, >> struct bio_set *bs, >> unsigned *nr_segs) >> { >> + unsigned int max_sectors, q_max_sectors; >> + unsigned int bio_segs = bio->bi_vcnt; >> + >> /* >> * All drivers must accept single-segments bios that are <= >> * PAGE_SIZE. This is a quick and dirty check that relies on >> @@ -303,14 +306,32 @@ static inline struct bio *blk_bio_segment_split(struct request_queue *q, >> * are cloned, but compared to the performance impact of cloned >> * bios themselves the loop below doesn't matter anyway. >> */ >> - if (!q->limits.chunk_sectors && bio->bi_vcnt == 1 && >> + if (!q->limits.chunk_sectors && bio_segs == 1 && >> (bio->bi_io_vec[0].bv_len + >> bio->bi_io_vec[0].bv_offset) <= PAGE_SIZE) { >> *nr_segs = 1; >> return NULL; >> } >> >> - return __blk_bio_segment_split(q, bio, bs, nr_segs); >> + q_max_sectors = get_max_io_size(q, bio); >> + if (!queue_virt_boundary(q) && bio_segs < queue_max_segments(q) && >> + bio->bi_iter.bi_size <= queue_max_segment_size(q)) { > > .bi_vcnt is 0 for fast cloned bio, so the above check may become true > when real nr_segment is > queue_max_segments(), especially in case that > max segments limit is small and segment size is big. I guess we can skip the fast path for them (i.e. bi_vcnt == 0) I'm curious, why it's 0 but not the real number? -- Pavel Begunkov