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[221.255.142.61]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-11df76edd4fsm71897034c88.8.2025.12.09.14.11.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Dec 2025 14:11:56 -0800 (PST) Message-ID: <4acab1b8-f67e-454b-a493-ac4c00193c51@kernel.dk> Date: Tue, 9 Dec 2025 15:11:54 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mq-deadline: the dd->dispatch queue follows a FIFO policy To: Tao pilgrim , Bart Van Assche Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Chengkaitao References: <20251208110213.92884-1-pilgrimtao@gmail.com> <33dcc737-1419-4f3e-8952-2f34db47a087@acm.org> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 12/8/25 7:06 PM, Tao pilgrim wrote: > However, now all requests in the dd->dispatch list carry > the BLK_MQ_INSERT_AT_HEAD flag, and I can't find any justification for > continuing to use a LIFO (last-in-first-out) policy. What if a head insertion requires another TUR or similar before being able to be processed? I agree with notion that AT_HEAD should generally be issued in order, but let's not make blanket changes like this just because you can't find any immediate justification for why the current behavior is as it is. It'd be different if you were fixing a bug and came across this. But that does not seem to be the case. -- Jens Axboe