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([2a01:4b00:bd21:4f00:7cc6:d3ca:494:116c]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b885b7661f7sm287380466b.54.2026.01.24.08.30.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 24 Jan 2026 08:30:26 -0800 (PST) Message-ID: <38a46172-8734-462b-870d-39d0697882e1@gmail.com> Date: Sat, 24 Jan 2026 16:30:25 +0000 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 v2] io_uring/rsrc: fix RLIMIT_MEMLOCK bypass by removing cross-buffer accounting To: Jens Axboe , Yuhao Jiang Cc: io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260119071039.2113739-1-danisjiang@gmail.com> <2919f3c5-2510-4e97-ab7f-c9eef1c76a69@kernel.dk> <8c6a9114-82e9-416e-804b-ffaa7a679ab7@kernel.dk> <2be71481-ac35-4ff2-b6a9-a7568f81f728@gmail.com> <2fcf583a-f521-4e8d-9a89-0985681ca85b@kernel.dk> <3b7e6088-7d92-4d5c-96c7-f8c0e2cc7745@kernel.dk> <596bc7ac-3d24-43a7-9e7e-e59189525ebc@gmail.com> <654fe339-5a2b-4c38-9d2d-28cfc306b307@kernel.dk> <9317bad6-aa89-4e93-b7d2-9e28f5d17cc8@gmail.com> <74f2ec89-ca40-44a0-8df7-de404063a1a3@kernel.dk> <32b884bc-929b-4b27-ae74-5754fa2473de@kernel.dk> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <32b884bc-929b-4b27-ae74-5754fa2473de@kernel.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/24/26 15:55, Jens Axboe wrote: > On 1/24/26 8:14 AM, Jens Axboe wrote: >>>> ________________________________________________________ >>>> Executed in 2.81 secs fish external >>>> usr time 0.71 secs 497.00 micros 0.71 secs >>>> sys time 19.57 secs 183.00 micros 19.57 secs >>>> >>>> which isn't insane. Obviously also needs conditional rescheduling in the >>>> page loops, as those can take a loooong time for large amounts of >>>> memory. >>> >>> 2.8 sec sounds like a lot as well, makes me wonder which part of >>> that is mm, but it mm should scale fine-ish. Surely there will be >>> contention on page refcounts but at least the table walk is >>> lockless in the best case scenario and otherwise seems to be read >>> protected by an rw lock. >> >> Well a lot of that is also just faulting in the memory on clear, test >> case should probably be modified to do its own timing. And iterating >> page arrays is a huge part of it too. There's no real contention in that >> 2.8 seconds. > > I checked and the faulting part is 2.0s of that runtime. On a re-run: Makes sense, I was forgetting it's full time. -- Pavel Begunkov