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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 2F01AC432BE for ; Tue, 3 Aug 2021 00:02:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 12FBC60F36 for ; Tue, 3 Aug 2021 00:02:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232540AbhHCACW (ORCPT ); Mon, 2 Aug 2021 20:02:22 -0400 Received: from mail-pj1-f45.google.com ([209.85.216.45]:52019 "EHLO mail-pj1-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232208AbhHCACV (ORCPT ); Mon, 2 Aug 2021 20:02:21 -0400 Received: by mail-pj1-f45.google.com with SMTP id mt6so27453947pjb.1 for ; Mon, 02 Aug 2021 17:02:11 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=5VClwSe2etPXE/OSrx9J4imLXZEz3r6MKLZhHcSuv8c=; b=QYQQDNA+LZwp1Ct6xTSqxglWbtGzKI0HOy9uOKftmLbg1i/v6NZIpxKmDjR16cYiXf kK1Bjw4xnpiqDnr1EGD4AmGefWt1XGom3/0Xn0Iqf1WHtxlelZ+6gj4HwPiiEUmFZ6X4 nyagbS8zROAr5bV+kLqWqiJU2SFcFSex3jZQeZiECi7io79KwSLKCtkjqAPI8ifj3fg8 T9TUqqzU7FW/mKwY9sATN/aMjB21L5FY7FkR4F44VCcSqT+P9Pv/ZiWYaBrHnsuwPrCA mgw/jeOaXl8my48frjycV2IxuqGXSjRQD4ieuB6Mw2AdVDW88idEIFyWUrsdyC7K2tLY DwoQ== X-Gm-Message-State: AOAM531QSD5jGNLQP1Lqz8sXfNn5cagwSJfIqtHrqGM8RmyRKDYyrJly BEXX/Te98MM+KhE6Wgil1a4= X-Google-Smtp-Source: ABdhPJyEpYXgCKmbRuKgfHhtW3pBlWjwea9zJ16YPkknUiTzRWPbWGiUz99b74LbMQAfHYOqL7My3w== X-Received: by 2002:a17:90a:f002:: with SMTP id bt2mr20363349pjb.142.1627948930701; Mon, 02 Aug 2021 17:02:10 -0700 (PDT) Received: from bvanassche-linux.mtv.corp.google.com ([2620:15c:211:1:bca4:545f:af00:8cbe]) by smtp.gmail.com with ESMTPSA id s7sm12712988pfk.12.2021.08.02.17.02.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Aug 2021 17:02:10 -0700 (PDT) From: Bart Van Assche To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Jaegeuk Kim , Bart Van Assche , Ming Lei , Tetsuo Handa , Martijn Coenen Subject: [PATCH 1/2] loop: Prevent that an I/O scheduler is assigned Date: Mon, 2 Aug 2021 17:01:59 -0700 Message-Id: <20210803000200.4125318-2-bvanassche@acm.org> X-Mailer: git-send-email 2.32.0.554.ge1b32706d8-goog In-Reply-To: <20210803000200.4125318-1-bvanassche@acm.org> References: <20210803000200.4125318-1-bvanassche@acm.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Loop devices have a single hardware queue. Hence, the block layer function elevator_get_default() selects the mq-deadline scheduler for loop devices. Using the mq-deadline scheduler or any other I/O scheduler for loop devices incurs unnecessary overhead. Make the loop driver pass the flag BLK_MQ_F_NOSCHED to the block layer core such that no I/O scheduler can be associated with block devices. This approach has an advantage compared to letting udevd change the loop I/O scheduler to none, namely that synchronize_rcu() does not get called. It is intentional that the flag BLK_MQ_F_SHOULD_MERGE is preserved. This patch reduces the Android boot time on my test setup with 0.5 seconds. Cc: Ming Lei Cc: Tetsuo Handa Cc: Christoph Hellwig Cc: Martijn Coenen Cc: Jaegeuk Kim Signed-off-by: Bart Van Assche --- drivers/block/loop.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index f8486d9b75a4..9fca3ab3988d 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -2333,7 +2333,8 @@ static int loop_add(int i) lo->tag_set.queue_depth = 128; lo->tag_set.numa_node = NUMA_NO_NODE; lo->tag_set.cmd_size = sizeof(struct loop_cmd); - lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_STACKING; + lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_STACKING | + BLK_MQ_F_NO_SCHED; lo->tag_set.driver_data = lo; err = blk_mq_alloc_tag_set(&lo->tag_set);