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Wed, 10 Sep 2025 04:56:38 -0700 (PDT) Message-ID: Date: Wed, 10 Sep 2025 12:57:42 +0100 Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/5] io_uring: avoid uring_lock for IORING_SETUP_SINGLE_ISSUER To: Jens Axboe , Caleb Sander Mateos Cc: io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250904170902.2624135-1-csander@purestorage.com> <175742490970.76494.10067269818248850302.b4-ty@kernel.dk> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <175742490970.76494.10067269818248850302.b4-ty@kernel.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/9/25 14:35, Jens Axboe wrote: > > On Thu, 04 Sep 2025 11:08:57 -0600, Caleb Sander Mateos wrote: >> As far as I can tell, setting IORING_SETUP_SINGLE_ISSUER when creating >> an io_uring doesn't actually enable any additional optimizations (aside >> from being a requirement for IORING_SETUP_DEFER_TASKRUN). This series >> leverages IORING_SETUP_SINGLE_ISSUER's guarantee that only one task >> submits SQEs to skip taking the uring_lock mutex in the submission and >> task work paths. >> >> [...] > > Applied, thanks! > > [1/5] io_uring: don't include filetable.h in io_uring.h > commit: 5d4c52bfa8cdc1dc1ff701246e662be3f43a3fe1 > [2/5] io_uring/rsrc: respect submitter_task in io_register_clone_buffers() > commit: 2f076a453f75de691a081c89bce31b530153d53b > [3/5] io_uring: clear IORING_SETUP_SINGLE_ISSUER for IORING_SETUP_SQPOLL > commit: 6f5a203998fcf43df1d43f60657d264d1918cdcd > [4/5] io_uring: factor out uring_lock helpers > commit: 7940a4f3394a6af801af3f2bcd1d491a71a7631d > [5/5] io_uring: avoid uring_lock for IORING_SETUP_SINGLE_ISSUER > commit: 4cc292a0faf1f0755935aebc9b288ce578d0ced2 FWIW, from a glance that should be quite broken, there is a bunch of bits protected from parallel use by the lock. I described this optimisation few years back around when first introduced SINGLE_ISSUER and the DEFER_TASKRUN locking model, but to this day think it's not worth it as it'll be a major pain for any future changes. It would've been more feasible if links wasn't a thing. Though, none of it is my problem anymore, and I'm not insisting. -- Pavel Begunkov