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Thu, 18 Jan 2024 10:56:12 -0800 (PST) Received: from [192.168.1.116] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id a10-20020a5d980a000000b007bf45b1c049sm2243874iol.0.2024.01.18.10.56.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 18 Jan 2024 10:56:11 -0800 (PST) Message-ID: <248b7070-a7c6-456d-99be-c3fff6f94f5e@kernel.dk> Date: Thu, 18 Jan 2024 11:56:11 -0700 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] block/mq-deadline: fallback to per-cpu insertion buckets under contention Content-Language: en-US To: Bart Van Assche , linux-block@vger.kernel.org References: <20240118180541.930783-1-axboe@kernel.dk> <20240118180541.930783-3-axboe@kernel.dk> <0ca63d05-fc5b-4e6a-a828-52eb24305545@acm.org> From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/18/24 11:53 AM, Bart Van Assche wrote: > On 1/18/24 10:33, Jens Axboe wrote: >> On 1/18/24 11:31 AM, Bart Van Assche wrote: >>> On 1/18/24 10:04, Jens Axboe wrote: >>>> If we attempt to insert a list of requests but someone else is already >>>> running an insertion, then fallback to queueing it internally and let >>>> the existing inserter finish the operation. >>> >>> Because this patch adds significant complexity: what are the use cases >>> that benefit from this kind of optimization? Are these perhaps workloads >>> on systems with many CPU cores and fast storage? If the storage is fast, >>> why to use mq-deadline instead of "none" as I/O-scheduler? >> >> You and others complain that mq-deadline is slow and doesn't scale, >> these two patches help improve that situation. Not sure why this is even >> a question? > > How much does this patch improve performance? Do you need me to link the cover letter that you were CC'ed on? -- Jens Axboe