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Tue, 11 Feb 2020 12:37:27 -0800 (PST) Received: from [192.168.43.18] ([109.126.145.62]) by smtp.gmail.com with ESMTPSA id s8sm5152424wmh.26.2020.02.11.12.37.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Feb 2020 12:37:26 -0800 (PST) Subject: Re: [RFC] do_hashed and wq enqueue To: Jens Axboe , io-uring References: <00a3935a-043a-ee60-2206-2e62ec8c2936@kernel.dk> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: <31a63d75-5022-a427-d123-90b2e2ca6350@gmail.com> Date: Tue, 11 Feb 2020 23:36:45 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <00a3935a-043a-ee60-2206-2e62ec8c2936@kernel.dk> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="zcADxSWOdNcyYTEBPaqvdoVyWrK9NLyKg" Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --zcADxSWOdNcyYTEBPaqvdoVyWrK9NLyKg Content-Type: multipart/mixed; boundary="Prpz8ZaYCrVfJm3IqM7NFSUFh58gjWo71"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , io-uring Message-ID: <31a63d75-5022-a427-d123-90b2e2ca6350@gmail.com> Subject: Re: [RFC] do_hashed and wq enqueue References: <00a3935a-043a-ee60-2206-2e62ec8c2936@kernel.dk> In-Reply-To: <00a3935a-043a-ee60-2206-2e62ec8c2936@kernel.dk> --Prpz8ZaYCrVfJm3IqM7NFSUFh58gjWo71 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 11/02/2020 23:30, Jens Axboe wrote: > On 2/11/20 1:20 PM, Pavel Begunkov wrote: >> Hi, >> >> I've been looking for hashed io-wq enqueuing, but not fully understand= the >> issue. As I remember, it was something about getting around blocking f= or >> buffered I/O. Is that so? Is there any write-up of a thread for this i= ssue? >=20 > Not sure if there's a writeup, but the issue is that buffered writes al= l > need to grab the per-inode mutex. Hence if you don't serialize these wr= ites, > you end up having potentially quite a few threads banging on the same m= utex. > This causes a high level of lock contention (and scheduling). By serial= izing > by inode hash we avoid that, and yield the same performance. >=20 > Dave Chinner is working on lifting this restriction, at which point we'= ll > have to gate the hashing based on whether or not the fs is smart or dum= b > when it comes to buffered writes and locking. Got it, thanks! >> My case is 2-fd request, and I'm not sure how it should look. For spli= ce() it's >> probably Ok to hash the non-pipe end (if any), but I wonder how it sho= uld work, >> if, for example, the restriction will be removed. >=20 > Probably just do the same, but for the output fd only (and following th= e > same restrictions in terms of file type). >=20 --=20 Pavel Begunkov --Prpz8ZaYCrVfJm3IqM7NFSUFh58gjWo71-- --zcADxSWOdNcyYTEBPaqvdoVyWrK9NLyKg Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl5DEF0ACgkQWt5b1Glr +6WnyxAAuP14nGCHGIt3/E2mkaWFjo57ezoh3pto3BKThMFrKXwCu3wgnKoE2oZc kA0rXv+TSk4eDlcmSFID5rn/hwVqh9Qp3r2wYa/IS39887En4Wgs5TjQ3QMImRZx stoHvQ8Iqhe4BdosQGLqyN0Wpay3y3TRs3faye6FIfEnw8iEWTUBarEiEBkpzr7v m2CEMqO9LSkf/kCUgIW6tqaRr3Rxh6mDCFkQ92ZwKzgqVxYnlti0jZPkCS7DvJSG DjTdfgAX3t184slGfAW9+VUe2maKiaaU8Hdp7cCiU1Z8cyDfmPwcU9cS4/CfNzOB SiOcuIln0kFQynOCpWNb0TlNgbXfEE7dSQdAdGLBCc6RuBjm7FnmOApKYdvcOIpg /TX1MMCRzqvXXABcEln3MWAC0s9nHlXltR4vZo8hWfF7u1E8fp+Y5VuosjZvdCbI wUsPswnQcB77QCD74S7tZQU66ZPRk7dj41YyBrs3iMKRyatKbyyCRJaWz3ImQwT4 5rtC376U5DAzyVo7/9VYeJDPykfnPh7ovwsJ4dTYnKzOC0sinBvym1VhWT11pUdS ozeWmgIj3Z46+RDZlf0wHFPi9DwuONe2LutBi+8LGggbIKir2ckfP7VnCvRphEkT lgX2rUaBlDil9C7h07D5470PVFUA9lhPKY0oRkBxBCHdyCwSEgo= =SIAx -----END PGP SIGNATURE----- --zcADxSWOdNcyYTEBPaqvdoVyWrK9NLyKg--