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Tue, 4 Oct 2022 15:40:28 -0700 (PDT) Received: from [10.225.163.106] (unknown [10.225.163.106]) by usg-ed-osssrv.wdc.com (Postfix) with ESMTPSA id 4Mht2M5VC4z1RvLy; Tue, 4 Oct 2022 15:40:27 -0700 (PDT) Message-ID: <7e3a521e-acf7-c3a8-a29b-c51874862344@opensource.wdc.com> Date: Wed, 5 Oct 2022 07:40:26 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.1 Subject: Re: [PATCH] block: allow specifying default iosched in config Content-Language: en-US To: Khazhy Kumykov Cc: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <20220926220134.2633692-1-khazhy@google.com> From: Damien Le Moal Organization: Western Digital Research In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_MED, SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/5/22 03:33, Khazhy Kumykov wrote: > On Mon, Oct 3, 2022 at 11:12 PM Damien Le Moal > wrote: >> >> This will allow a configuration to specify bfq or kyber for all single queue >> devices > That's the idea >> , which include SMR HDDs. Since these can only use mq-deadline (or none >> if the user like living dangerously), this default config-based solution is not >> OK in my opinion. > I don't think this is true - elevator_init_mq will call > elevator_get_by_features, not elevator_get_default for SMR hdds (and > other zoned devices), as it sets required_elevator_features. OK, but my point remains: why not use a udev rule ? Why add a config option to hardcode the default scheduler ? Most average users will have no idea which one to choose... >> >> What is wrong with using a udev rule to set the default disk scheduler ? Most >> distros do that already anyway, so this config may not even be that useful in >> practice. What is the use case here ? >> >> >> -- >> Damien Le Moal >> Western Digital Research >> -- Damien Le Moal Western Digital Research