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 59EDEC2BBCF for ; Tue, 15 Dec 2020 11:46:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 224AD22285 for ; Tue, 15 Dec 2020 11:46:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728656AbgLOLpu (ORCPT ); Tue, 15 Dec 2020 06:45:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45058 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726951AbgLOLpM (ORCPT ); Tue, 15 Dec 2020 06:45:12 -0500 Received: from mail-wm1-x343.google.com (mail-wm1-x343.google.com [IPv6:2a00:1450:4864:20::343]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DBF48C06179C; Tue, 15 Dec 2020 03:44:31 -0800 (PST) Received: by mail-wm1-x343.google.com with SMTP id y23so18218419wmi.1; Tue, 15 Dec 2020 03:44:31 -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=OWwRZGVysOGW0Xc4n3DjuAEe5aIQZl9wIJ+AWET/hOI=; b=AMTXx6TTD352jGB3PrcCaEUiWdJOssWhewuqsduGuOThnSCQisHMFsZyAmf9shugqg 7f+Fn+gtQt6d9DzpHbl4i125FZLTs+IFwStWEmYnOWee7YEHGIZzH8e1fTeSln0M/Z3r RAgikd05DcfIGb8X6fo0tFoVQGB9amDOkHABBfO4vafld96bwNPGQkbscaPJWwu9d3WQ etev0b7CCnBCptzleYf/IGvGcnP/Zb3mst6FzLAYlqBoauUdpk1FAeNQqH3GoFcNAmZm QRRwsh9PmutkLvBJuK5bXstcxKpB3+8nJbVWdZ94ZQVMGbhRdh4iDe2Zw7gb1ljUXdY9 X9HQ== 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=OWwRZGVysOGW0Xc4n3DjuAEe5aIQZl9wIJ+AWET/hOI=; b=ap5bVjbqshVJCRXTSzHA1M+PphySxMD4SWjNZw+6KDYONjdwtkyCSgOid4B0gbHEy2 q9xTIxUAqzcd8iuiZjEi2Bq2gWgXZpZm7MPdO4XrfEhbDCcXe7q4EIR5B3fGDyjd3hny DO5LVEoR6RB05ISi1e3HlRRq5SOoXPE2VJbFN3bSQD5KNT115eRC43kBzj+86mQ/eZuZ snvqURGK0psw2RFvw1/V7AGVTy4dSZm7trTD4/hM+9wk/t5zud1NB/CGZgAl1w/DRGK4 yyDrOPe80/yj123XHT5pQq5mktmO6NrqycbOzbXwY2dHoFYhoGRN6CSOW3rr8iRNgFIw xVrQ== X-Gm-Message-State: AOAM531iiSY0NUq6DpET1fto2ns0c7YAK+fdDuv/5olxfOfPBANf/yjT 7Os+CiiCsQe6c0cd0/noQTgMgQQDiDT5bRaq X-Google-Smtp-Source: ABdhPJxZhWNo4K56HmDD6LuDz+9jky+iOr3Bue398Aop8a3uegKgJUFzW4i5BXY8aVFtVsIW94CryA== X-Received: by 2002:a7b:c145:: with SMTP id z5mr32397755wmi.164.1608032670438; Tue, 15 Dec 2020 03:44:30 -0800 (PST) Received: from [192.168.8.128] ([185.69.145.6]) by smtp.gmail.com with ESMTPSA id b14sm36954767wrx.77.2020.12.15.03.44.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 15 Dec 2020 03:44:29 -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: <1d3cf86668e44b3a3d35b5dbe759a086a157e434.1607976425.git.asml.silence@gmail.com> <20201215005659.GF632069@dread.disaster.area> <20201215013312.GK632069@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 4/6] block/psi: remove PSI annotations from direct IO Message-ID: Date: Tue, 15 Dec 2020 11:41:11 +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: <20201215013312.GK632069@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 01:33, Dave Chinner wrote: > On Tue, Dec 15, 2020 at 01:03:45AM +0000, Pavel Begunkov wrote: >> On 15/12/2020 00:56, Dave Chinner wrote: >>> On Tue, Dec 15, 2020 at 12:20:23AM +0000, Pavel Begunkov wrote: >>>> As reported, we must not do pressure stall information accounting for >>>> direct IO, because otherwise it tells that it's thrashing a page when >>>> actually doing IO on hot data. >>>> >>>> Apparently, bio_iov_iter_get_pages() is used only by paths doing direct >>>> IO, so just make it avoid setting BIO_WORKINGSET, it also saves us CPU >>>> cycles on doing that. For fs/direct-io.c just clear the flag before >>>> submit_bio(), it's not of much concern performance-wise. >>>> >>>> Reported-by: Christoph Hellwig >>>> Suggested-by: Christoph Hellwig >>>> Suggested-by: Johannes Weiner >>>> Signed-off-by: Pavel Begunkov >>>> --- >>>> block/bio.c | 25 ++++++++++++++++--------- >>>> fs/direct-io.c | 2 ++ >>>> 2 files changed, 18 insertions(+), 9 deletions(-) >>> ..... >>>> @@ -1099,6 +1103,9 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter) >>>> * fit into the bio, or are requested in @iter, whatever is smaller. If >>>> * MM encounters an error pinning the requested pages, it stops. Error >>>> * is returned only if 0 pages could be pinned. >>>> + * >>>> + * It also doesn't set BIO_WORKINGSET, so is intended for direct IO. If used >>>> + * otherwise the caller is responsible to do that to keep PSI happy. >>>> */ >>>> int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) >>>> { >>>> diff --git a/fs/direct-io.c b/fs/direct-io.c >>>> index d53fa92a1ab6..914a7f600ecd 100644 >>>> --- a/fs/direct-io.c >>>> +++ b/fs/direct-io.c >>>> @@ -426,6 +426,8 @@ static inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio) >>>> unsigned long flags; >>>> >>>> bio->bi_private = dio; >>>> + /* PSI is only for paging IO */ >>>> + bio_clear_flag(bio, BIO_WORKINGSET); >>> >>> Why only do this for the old direct IO path? Why isn't this >>> necessary for the iomap DIO path? >> >> It's in the description. In short, block and iomap dio use >> bio_iov_iter_get_pages(), which with this patch doesn't use >> [__]bio_add_page() and so doesn't set the flag. > > That is not obvious to someone not intimately familiar with the > patchset you are working on. You described -what- the code is doing, > not -why- the flag needs to be cleared here. It's missing the link between BIO_WORKINGSET and PSI, but otherwise it describe both, what it does and how. I'll reword it for you next iteration. > > "Direct IO does not operate on the current working set of pages > managed by the kernel, so it should not be accounted as IO to the > pressure stall tracking infrastructure. Only direct IO paths use > bio_iov_iter_get_pages() to build bios, so to avoid PSI tracking of > direct IO don't flag the bio with BIO_WORKINGSET in this function. > > fs/direct-io.c uses to build the bio we > are going to submit and so still flags the bio with BIO_WORKINGSET. > Rather than convert it to use bio_iov_iter_get_pages() to avoid > flagging the bio, we simply clear the BIO_WORKINGSET flag before > submitting the bio." > > Cheers, > > Dave. > -- Pavel Begunkov