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Thu, 18 Jan 2024 10:33:29 -0800 (PST) Received: from [192.168.1.116] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id t15-20020a05663801ef00b0046d4105b7e8sm1129940jaq.49.2024.01.18.10.33.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 18 Jan 2024 10:33:28 -0800 (PST) Message-ID: Date: Thu, 18 Jan 2024 11:33:28 -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: <0ca63d05-fc5b-4e6a-a828-52eb24305545@acm.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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? -- Jens Axboe