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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8FF4C433F5 for ; Thu, 10 Feb 2022 09:19:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235240AbiBJJTl (ORCPT ); Thu, 10 Feb 2022 04:19:41 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:46048 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238391AbiBJJTl (ORCPT ); Thu, 10 Feb 2022 04:19:41 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D496F10B3; Thu, 10 Feb 2022 01:19:41 -0800 (PST) Received: from dggpemm500022.china.huawei.com (unknown [172.30.72.53]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4JvWPV1Sttz9sXd; Thu, 10 Feb 2022 17:18:06 +0800 (CST) Received: from dggpemm500002.china.huawei.com (7.185.36.229) by dggpemm500022.china.huawei.com (7.185.36.162) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Thu, 10 Feb 2022 17:19:24 +0800 Received: from localhost.localdomain.localdomain (10.175.113.25) by dggpemm500002.china.huawei.com (7.185.36.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Thu, 10 Feb 2022 17:19:24 +0800 From: Xiongfeng Wang To: , CC: , , , , Subject: [RFC PATCH] blk-mq: avoid housekeeping CPUs scheduling a worker on a non-housekeeping CPU Date: Thu, 10 Feb 2022 17:35:32 +0800 Message-ID: <20220210093532.182818-1-wangxiongfeng2@huawei.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.113.25] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500002.china.huawei.com (7.185.36.229) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org When NOHZ_FULL is enabled, such as in HPC situation, CPUs are divided into housekeeping CPUs and non-housekeeping CPUs. Non-housekeeping CPUs are NOHZ_FULL CPUs and are often monopolized by the userspace process, such HPC application process. Any sort of interruption is not expected. blk_mq_hctx_next_cpu() selects each cpu in 'hctx->cpumask' alternately to schedule the work thread blk_mq_run_work_fn(). When 'hctx->cpumask' contains housekeeping CPU and non-housekeeping CPU at the same time, a housekeeping CPU, which want to request a IO, may schedule a worker on a non-housekeeping CPU. This may affect the performance of the userspace application running on non-housekeeping CPUs. So let's just schedule the worker thread on the current CPU when the current CPU is housekeeping CPU. Signed-off-by: Xiongfeng Wang --- block/blk-mq.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 1adfe4824ef5..ff9a4bf16858 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #include #include @@ -2036,6 +2037,8 @@ static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx) static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async, unsigned long msecs) { + int work_cpu; + if (unlikely(blk_mq_hctx_stopped(hctx))) return; @@ -2050,7 +2053,17 @@ static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async, put_cpu(); } - kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work, + /* + * Avoid housekeeping CPUs scheduling a worker on a non-housekeeping + * CPU + */ + if (tick_nohz_full_enabled() && housekeeping_cpu(smp_processor_id(), + HK_FLAG_WQ)) + work_cpu = smp_processor_id(); + else + work_cpu = blk_mq_hctx_next_cpu(hctx); + + kblockd_mod_delayed_work_on(work_cpu, &hctx->run_work, msecs_to_jiffies(msecs)); } -- 2.20.1