From patchwork Fri Apr 28 07:44:04 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hou Tao X-Patchwork-Id: 13226018 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D3B9AC77B7E for ; Fri, 28 Apr 2023 07:13:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345452AbjD1HN2 (ORCPT ); Fri, 28 Apr 2023 03:13:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60378 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345455AbjD1HNZ (ORCPT ); Fri, 28 Apr 2023 03:13:25 -0400 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 07194448C; Fri, 28 Apr 2023 00:13:15 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.30.67.153]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4Q73jM4mF9z4f3jZC; Fri, 28 Apr 2023 15:13:11 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.124.27]) by APP4 (Coremail) with SMTP id gCh0CgD3X7MEcktkqe5AIQ--.42318S4; Fri, 28 Apr 2023 15:13:10 +0800 (CST) From: Hou Tao To: linux-block@vger.kernel.org, Jens Axboe Cc: Bart Van Assche , Jan Kara , Bagas Sanjaya , Chaitanya Kulkarni , cgroups@vger.kernel.org, Tejun Heo , Zefan Li , Johannes Weiner , Jonathan Corbet , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, houtao1@huawei.com Subject: [PATCH v4] blk-ioprio: Introduce promote-to-rt policy Date: Fri, 28 Apr 2023 15:44:04 +0800 Message-Id: <20230428074404.280532-1-houtao@huaweicloud.com> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 X-CM-TRANSID: gCh0CgD3X7MEcktkqe5AIQ--.42318S4 X-Coremail-Antispam: 1UD129KBjvJXoW3GF1ftF4UWrW3trWrKr1kuFg_yoWxZr4rpF 4fAF9xur9YqF1xJFnrJ3WkXrWrtas2yw47WFsxKFyF93yjyw1DuF40yF1kWFyfA3yDXFZx XrZ8ArW0kFyDurJanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUkIb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x 0267AKxVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcxkI7VAKI48JM4IIrI8v6xkF7I0E8cxan2IY04v7MxAIw28I cxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2 IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI 42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwCI42 IY6xAIw20EY4v20xvaj40_Wr1j6rW3Jr1lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2 z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7IU1zuWJUUUUU== X-CM-SenderInfo: xkrx3t3r6k3tpzhluzxrxghudrp/ X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Hou Tao Since commit a78418e6a04c ("block: Always initialize bio IO priority on submit"), bio->bi_ioprio will never be IOPRIO_CLASS_NONE when calling blkcg_set_ioprio(), so there will be no way to promote the io-priority of one cgroup to IOPRIO_CLASS_RT, because bi_ioprio will always be greater than or equals to IOPRIO_CLASS_RT. It seems possible to call blkcg_set_ioprio() first then try to initialize bi_ioprio later in bio_set_ioprio(), but this doesn't work for bio in which bi_ioprio is already initialized (e.g., direct-io), so introduce a new promote-to-rt policy to promote the iopriority of bio to IOPRIO_CLASS_RT if the ioprio is not already RT. For none-to-rt policy, although it doesn't work now, but considering that its purpose was also to override the io-priority to RT and allowing for a smoother transition, just keep it and treat it as an alias of the promote-to-rt policy. Acked-by: Tejun Heo Reviewed-by: Bart Van Assche Reviewed-by: Chaitanya Kulkarni Reviewed-by: Jan Kara Signed-off-by: Hou Tao Reviewed-by: Bagas Sanjaya --- v4: * rebased on 33afd4b76393 * Add Reviewed-by from Jan Kara v3: https://lore.kernel.org/linux-block/20230223135154.3749088-1-houtao@huaweicloud.com * Use 'non-RT' instead of 'no-RT' in document (from Bagas) * Remove repeated sentence in commit message * Add Reviewed-by and Acked-by tags v2: https://lore.kernel.org/linux-block/20230220135428.2632906-1-houtao@huaweicloud.com * Simplify the implementation of promote-to-rt (from Bart) * Make none-to-rt to work again by treating it as an alias of the promote-to-rt policy (from Bart & Jan) * fix the style of new content in cgroup-v2.rst (from Bagas) * set the default priority level to 4 instead of 0 for promote-to-rt v1: https://lore.kernel.org/linux-block/20230201045227.2203123-1-houtao@huaweicloud.com Documentation/admin-guide/cgroup-v2.rst | 42 ++++++++++++++----------- block/blk-ioprio.c | 23 ++++++++++++-- 2 files changed, 44 insertions(+), 21 deletions(-) diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index f67c0829350b..7544ce00e0cb 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -2024,31 +2024,33 @@ that attribute: no-change Do not modify the I/O priority class. - none-to-rt - For requests that do not have an I/O priority class (NONE), - change the I/O priority class into RT. Do not modify - the I/O priority class of other requests. + promote-to-rt + For requests that have a non-RT I/O priority class, change it into RT. + Also change the priority level of these requests to 4. Do not modify + the I/O priority of requests that have priority class RT. restrict-to-be For requests that do not have an I/O priority class or that have I/O - priority class RT, change it into BE. Do not modify the I/O priority - class of requests that have priority class IDLE. + priority class RT, change it into BE. Also change the priority level + of these requests to 0. Do not modify the I/O priority class of + requests that have priority class IDLE. idle Change the I/O priority class of all requests into IDLE, the lowest I/O priority class. + none-to-rt + Deprecated. Just an alias for promote-to-rt. + The following numerical values are associated with the I/O priority policies: -+-------------+---+ -| no-change | 0 | -+-------------+---+ -| none-to-rt | 1 | -+-------------+---+ -| rt-to-be | 2 | -+-------------+---+ -| all-to-idle | 3 | -+-------------+---+ ++----------------+---+ +| no-change | 0 | ++----------------+---+ +| rt-to-be | 2 | ++----------------+---+ +| all-to-idle | 3 | ++----------------+---+ The numerical value that corresponds to each I/O priority class is as follows: @@ -2064,9 +2066,13 @@ The numerical value that corresponds to each I/O priority class is as follows: The algorithm to set the I/O priority class for a request is as follows: -- Translate the I/O priority class policy into a number. -- Change the request I/O priority class into the maximum of the I/O priority - class policy number and the numerical I/O priority class. +- If I/O priority class policy is promote-to-rt, change the request I/O + priority class to IOPRIO_CLASS_RT and change the request I/O priority + level to 4. +- If I/O priorityt class is not promote-to-rt, translate the I/O priority + class policy into a number, then change the request I/O priority class + into the maximum of the I/O priority class policy number and the numerical + I/O priority class. PID --- diff --git a/block/blk-ioprio.c b/block/blk-ioprio.c index 055529b9b92b..4051fada01f1 100644 --- a/block/blk-ioprio.c +++ b/block/blk-ioprio.c @@ -23,25 +23,28 @@ /** * enum prio_policy - I/O priority class policy. * @POLICY_NO_CHANGE: (default) do not modify the I/O priority class. - * @POLICY_NONE_TO_RT: modify IOPRIO_CLASS_NONE into IOPRIO_CLASS_RT. + * @POLICY_PROMOTE_TO_RT: modify no-IOPRIO_CLASS_RT to IOPRIO_CLASS_RT. * @POLICY_RESTRICT_TO_BE: modify IOPRIO_CLASS_NONE and IOPRIO_CLASS_RT into * IOPRIO_CLASS_BE. * @POLICY_ALL_TO_IDLE: change the I/O priority class into IOPRIO_CLASS_IDLE. + * @POLICY_NONE_TO_RT: an alias for POLICY_PROMOTE_TO_RT. * * See also . */ enum prio_policy { POLICY_NO_CHANGE = 0, - POLICY_NONE_TO_RT = 1, + POLICY_PROMOTE_TO_RT = 1, POLICY_RESTRICT_TO_BE = 2, POLICY_ALL_TO_IDLE = 3, + POLICY_NONE_TO_RT = 4, }; static const char *policy_name[] = { [POLICY_NO_CHANGE] = "no-change", - [POLICY_NONE_TO_RT] = "none-to-rt", + [POLICY_PROMOTE_TO_RT] = "promote-to-rt", [POLICY_RESTRICT_TO_BE] = "restrict-to-be", [POLICY_ALL_TO_IDLE] = "idle", + [POLICY_NONE_TO_RT] = "none-to-rt", }; static struct blkcg_policy ioprio_policy; @@ -189,6 +192,20 @@ void blkcg_set_ioprio(struct bio *bio) if (!blkcg || blkcg->prio_policy == POLICY_NO_CHANGE) return; + if (blkcg->prio_policy == POLICY_PROMOTE_TO_RT || + blkcg->prio_policy == POLICY_NONE_TO_RT) { + /* + * For RT threads, the default priority level is 4 because + * task_nice is 0. By promoting non-RT io-priority to RT-class + * and default level 4, those requests that are already + * RT-class but need a higher io-priority can use ioprio_set() + * to achieve this. + */ + if (IOPRIO_PRIO_CLASS(bio->bi_ioprio) != IOPRIO_CLASS_RT) + bio->bi_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_RT, 4); + return; + } + /* * Except for IOPRIO_CLASS_NONE, higher I/O priority numbers * correspond to a lower priority. Hence, the max_t() below selects