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Fri, 09 May 2025 06:57:56 -0700 (PDT) Received: from [127.0.0.1] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id e9e14a558f8ab-3da7e158bfcsm5455985ab.58.2025.05.09.06.57.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 May 2025 06:57:55 -0700 (PDT) From: Jens Axboe To: asml.silence@gmail.com, Gabriel Krisman Bertazi Cc: io-uring@vger.kernel.org In-Reply-To: <20250508181203.3785544-1-krisman@suse.de> References: <20250508181203.3785544-1-krisman@suse.de> Subject: Re: [PATCH] io_uring/sqpoll: Increase task_work submission batch size Message-Id: <174679907531.93446.7646054037339322559.b4-ty@kernel.dk> Date: Fri, 09 May 2025 07:57:55 -0600 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Mailer: b4 0.14.3-dev-7b9b9 On Thu, 08 May 2025 14:12:03 -0400, Gabriel Krisman Bertazi wrote: > Our QA team reported a 10%-23%, throughput reduction on an io_uring > sqpoll testcase doing IO to a null_blk, that I traced back to a > reduction of the device submission queue depth utilization. It turns out > that, after commit af5d68f8892f ("io_uring/sqpoll: manage task_work > privately"), we capped the number of task_work entries that can be > completed from a single spin of sqpoll to only 8 entries, before the > sqpoll goes around to (potentially) sleep. While this cap doesn't drive > the submission side directly, it impacts the completion behavior, which > affects the number of IO queued by fio per sqpoll cycle on the > submission side, and io_uring ends up seeing less ios per sqpoll cycle. > As a result, block layer plugging is less effective, and we see more > time spent inside the block layer in profilings charts, and increased > submission latency measured by fio. > > [...] Applied, thanks! [1/1] io_uring/sqpoll: Increase task_work submission batch size (no commit info) Best regards, -- Jens Axboe