From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dggsgout11.his.huawei.com (unknown [45.249.212.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D0178157E7D; Fri, 14 Jun 2024 01:07:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718327232; cv=none; b=JdlSymMPzaXm5v39j4Cpe2SwvRbCf5frMjvV5RBVu4XeriNa62bdOb4ovl8vWhKFrl29P1mBdLlYhRH3yVJJuWgdiuVNmx1d4kla3UKN6nCl4SbtI9CSSBStmFjFDS+WDLPm/NVw1cZuou91dOyFWUzoJDoaHUtiLCJYufcCVno= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718327232; c=relaxed/simple; bh=2tC/fV53SlYxr1+Tb0Q8m2wjAfrkmL7OuJnZr23PIcI=; h=Subject:To:Cc:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=bflDOy65M6cJWLNCLlk6rNt+vt51vQzbGYFC08e13BaYKsVuyCtYDOd1IBV6/FoI0tpportg4FzaVHE6Ti5OWqsZIi0AL8t7IRuvzwOF/Bwwu5DXlIGAt439cjNEtdZAzmE6avIrM/WXmGAhTo3YbQ1deIbpIipPQvRMBgE8IAg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.93.142]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4W0h262P9Fz4f3mHq; Fri, 14 Jun 2024 09:06:54 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id D76B71A0185; Fri, 14 Jun 2024 09:07:05 +0800 (CST) Received: from [10.174.176.73] (unknown [10.174.176.73]) by APP1 (Coremail) with SMTP id cCh0CgBnOBG3l2tmQXutPQ--.44541S3; Fri, 14 Jun 2024 09:07:05 +0800 (CST) Subject: Re: [PATCH RFC -next 0/7] blk-iocost: support to build iocost as kernel module To: Bart Van Assche , Greg KH , Yu Kuai Cc: axboe@kernel.dk, tj@kernel.org, josef@toxicpanda.com, lizefan.x@bytedance.com, hannes@cmpxchg.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com, "yukuai (C)" References: <20240613014937.1326020-1-yukuai1@huaweicloud.com> <2024061342-walk-cavalier-7e48@gregkh> <97a2b888-4dac-451c-bb9c-40d8dc52cd60@acm.org> From: Yu Kuai Message-ID: <6bfbe267-8a75-486c-877b-e3236cddfa93@huaweicloud.com> Date: Fri, 14 Jun 2024 09:07:03 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <97a2b888-4dac-451c-bb9c-40d8dc52cd60@acm.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID:cCh0CgBnOBG3l2tmQXutPQ--.44541S3 X-Coremail-Antispam: 1UD129KBjvdXoW7XF1DKFWUZw15CFWrCw1Utrb_yoWDWFgEv3 Z5ZFyjqryxWayDAw1qyFs0qrWkKr4ruw4jy34UWayUKFn5tFnYyw1rX34kZFn8GF47Crn5 uFy5XF1ktF1YgjkaLaAFLSUrUUUUUb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUIcSsGvfJTRUUUb3AFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k26cxKx2IYs7xG 6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8w A2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j 6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oV Cq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0 I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r 4UM4x0Y48IcVAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2kI c2xKxwCYjI0SjxkI62AI1cAE67vIY487MxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4 AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE 17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMI IF0xvE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_WFyUJVCq 3wCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCT nIWIevJa73UjIFyTuYvjfUoOJ5UUUUU X-CM-SenderInfo: 51xn3trlr6x35dzhxuhorxvhhfrp/ Hi, 在 2024/06/14 0:15, Bart Van Assche 写道: > On 6/12/24 10:54 PM, Greg KH wrote: >> On Thu, Jun 13, 2024 at 09:49:30AM +0800, Yu Kuai wrote: >>> From: Yu Kuai >>> >>> Yu Kuai (7): >>>    kernfs: export pr_cont_kernfs_path() >>>    cgroup: export cgroup_parse_float >>>    block: export some API >>>    blk-iocost: factor out helpers to handle params from ioc_qos_write() >>>    blk-iocost: parse params before initializing iocost >>>    blk-iocost: support to free iocost >>>    blk-iocost: support to build iocost as kernel module >> >> No where do you say _why_ building this as a module is a good idea. >> >> Why do this at all? > > With CONFIG_BLK_CGROUP_IOCOST=y (as in the Android kernel), the > blk-iocost kernel module causes a (small) runtime overhead, even if it > is not being used. I think this is not true... Because iocost is lazy initialized, and if iocost is not initialized, there should not be such overhead. Thanks, Kuai > > Thanks, > > Bart. > > > . >