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,URIBL_BLOCKED, 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 522B3C2BB40 for ; Tue, 15 Dec 2020 01:19:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED32721D42 for ; Tue, 15 Dec 2020 01:19:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729588AbgLOBTj (ORCPT ); Mon, 14 Dec 2020 20:19:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729395AbgLOBTj (ORCPT ); Mon, 14 Dec 2020 20:19:39 -0500 Received: from mail-wr1-x442.google.com (mail-wr1-x442.google.com [IPv6:2a00:1450:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8F7D4C061793; Mon, 14 Dec 2020 17:18:58 -0800 (PST) Received: by mail-wr1-x442.google.com with SMTP id 91so18213728wrj.7; Mon, 14 Dec 2020 17:18:58 -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=sThOrhp2Jm3ClsF9DN8GXzoj1By2BPC+ziqGGyYmU5A=; b=KM76NqpzcJSDKm3cruux4IlQHXvEhtmcz10NaKxb//LUYyGO1ASdDQBfEovObajuEj KWYqzIV1Kbzx6hOZsvXuKTicFgQ48/2MKZIbOBpycwNSXc9sbsQpSpK7kbUUhjnGkA8x q5kfmA+6GTt3OHmGh+AxvM15+H8404SAZWg0G7PzJZTJyTrGbB1JijfelwiPQKAImQJH 4Znn9m2RRDbAjoLYDXFyFHBZ0AYFHXRnLqJfhYdoscLi0DFKbC7Emw8uczphtYRvp1iQ IMV0MSrJUAvnzYD2lq7usdNfebh7pwQ/wyUjG8o1XNECJUmYmNwPbcHsxLsdbpCdM9Ki 0Z4Q== 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=sThOrhp2Jm3ClsF9DN8GXzoj1By2BPC+ziqGGyYmU5A=; b=uKxmq10580MOy0NpGGIkdbKq+bRY++vEXmuwnV8JbPeY1PjppBtXaFkL/7fSq5vNAZ Krm5PSCXHlcPejNUI0kwzhL0p61Hou9ObIAnKlfnkQ21zI0R3edsnylDjTDjFLjjl4Bi tCmhLdgXDjm30ldinglxvkE6I0Ca56A6MkOq8oAv7+RO3VopdKTC2zC3NC/sZYA1oI/M h65tNxgeeRMwMPxVumfQ96gjXqO1uLjUrz8Dogvh++oAcK4mOtSwtYwq3T+wnEYN3m5c 8bzy+lc5S0zFIb1DCM6aOrx7M5OZM2fDPolWzD55RlJD2HRaT+Q2lcGIxmZX1dG2k7rb 7zfQ== X-Gm-Message-State: AOAM531/89iuvuwn6op3AGxiN0K5rgNQE4QlCCu/FIEWWQtKND0ehDnW OCnvVyVOEhJFI+IFxXu/KmeYndAu4mx+dtAO X-Google-Smtp-Source: ABdhPJyzahnkaqmwFFVkAJTKRinIOi3K9sMDapjeEStepwDn+7cr4XNXPZWg4fgfpEG/Swb/DJgePg== X-Received: by 2002:adf:e64b:: with SMTP id b11mr31361359wrn.257.1607995137148; Mon, 14 Dec 2020 17:18:57 -0800 (PST) Received: from [192.168.8.128] ([85.255.232.163]) by smtp.gmail.com with ESMTPSA id t16sm35394801wri.42.2020.12.14.17.18.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Dec 2020 17:18:56 -0800 (PST) To: Dave Chinner Cc: linux-block@vger.kernel.org, Jens Axboe , Christoph Hellwig , Matthew Wilcox , Ming Lei , Johannes Weiner , Alexander Viro , "Darrick J . Wong" , "Martin K . Petersen" , Jonathan Corbet , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, target-devel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-doc@vger.kernel.org References: <498b34d746627e874740d8315b2924880c46dbc3.1607976425.git.asml.silence@gmail.com> <20201215010921.GH632069@dread.disaster.area> 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: [PATCH v1 6/6] block/iomap: don't copy bvec for direct IO Message-ID: Date: Tue, 15 Dec 2020 01:15:37 +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: <20201215010921.GH632069@dread.disaster.area> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 15/12/2020 01:09, Dave Chinner wrote: > On Tue, Dec 15, 2020 at 12:20:25AM +0000, Pavel Begunkov wrote: >> The block layer spends quite a while in blkdev_direct_IO() to copy and >> initialise bio's bvec. However, if we've already got a bvec in the input >> iterator it might be reused in some cases, i.e. when new >> ITER_BVEC_FLAG_FIXED flag is set. Simple tests show considerable >> performance boost, and it also reduces memory footprint. >> >> Suggested-by: Matthew Wilcox >> Signed-off-by: Pavel Begunkov >> --- >> Documentation/filesystems/porting.rst | 9 ++++ >> block/bio.c | 64 +++++++++++---------------- >> include/linux/bio.h | 3 ++ >> 3 files changed, 38 insertions(+), 38 deletions(-) > > This doesn't touch iomap code, so the title of the patch seems > wrong... yeah, should be bio. > >> +For bvec based itererators bio_iov_iter_get_pages() now doesn't copy bvecs but >> +uses the one provided. Anyone issuing kiocb-I/O should ensure that the bvec and >> +page references stay until I/O has completed, i.e. until ->ki_complete() has >> +been called or returned with non -EIOCBQUEUED code. > > This is hard to follow. Perhaps: > > bio_iov_iter_get_pages() uses the bvecs provided for bvec based > iterators rather than copying them. Hence anyone issuing kiocb based > IO needs to ensure the bvecs and pages stay referenced until the > submitted I/O is completed by a call to ->ki_complete() or returns > with an error other than -EIOCBQUEUED. Agree, that's easier to read, thanks > >> diff --git a/include/linux/bio.h b/include/linux/bio.h >> index 2a9f3f0bbe0a..337f4280b639 100644 >> --- a/include/linux/bio.h >> +++ b/include/linux/bio.h >> @@ -444,6 +444,9 @@ static inline void bio_wouldblock_error(struct bio *bio) >> >> static inline int bio_iov_vecs_to_alloc(struct iov_iter *iter, int max_segs) >> { >> + /* reuse iter->bvec */ >> + if (iov_iter_is_bvec(iter)) >> + return 0; >> return iov_iter_npages(iter, max_segs); > > Ah, I'm a blind idiot... :/ > > Cheers, > > Dave. > -- Pavel Begunkov