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Mon, 16 Dec 2019 08:47:52 -0800 (PST) Received: from [192.168.43.176] ([109.126.149.134]) by smtp.gmail.com with ESMTPSA id w8sm408046wmd.2.2019.12.16.08.47.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 16 Dec 2019 08:47:52 -0800 (PST) To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <6256169d519f72fe592e70be47a04aa0e9c3b9a1.1576333754.git.asml.silence@gmail.com> <3a102881-3cc3-ba05-2f86-475145a87566@kernel.dk> <900dbb63-ae9e-40e6-94f9-8faa1c14389e@gmail.com> <9b422273-cee6-8fdb-0108-dc304e4b5ccb@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== Subject: Re: [PATCH v3] io_uring: don't wait when under-submitting Message-ID: <279b9435-6050-c15a-440d-c196c6184556@gmail.com> Date: Mon, 16 Dec 2019 19:47:23 +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: <9b422273-cee6-8fdb-0108-dc304e4b5ccb@kernel.dk> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="fia9c39BoNAzl6CFYfBiYunGN9SLhccnz" 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) --fia9c39BoNAzl6CFYfBiYunGN9SLhccnz Content-Type: multipart/mixed; boundary="6o2dx0fo4baOvOO1LsTLMrsxchoQg4tLP"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <279b9435-6050-c15a-440d-c196c6184556@gmail.com> Subject: Re: [PATCH v3] io_uring: don't wait when under-submitting References: <6256169d519f72fe592e70be47a04aa0e9c3b9a1.1576333754.git.asml.silence@gmail.com> <3a102881-3cc3-ba05-2f86-475145a87566@kernel.dk> <900dbb63-ae9e-40e6-94f9-8faa1c14389e@gmail.com> <9b422273-cee6-8fdb-0108-dc304e4b5ccb@kernel.dk> In-Reply-To: <9b422273-cee6-8fdb-0108-dc304e4b5ccb@kernel.dk> --6o2dx0fo4baOvOO1LsTLMrsxchoQg4tLP Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 16/12/2019 00:33, Jens Axboe wrote: > On 12/15/19 8:48 AM, Pavel Begunkov wrote: >> On 15/12/2019 08:42, Jens Axboe wrote: >>> On 12/14/19 11:43 AM, Jens Axboe wrote: >>>> On 12/14/19 7:53 AM, Pavel Begunkov wrote: >>>>> There is no reliable way to submit and wait in a single syscall, as= >>>>> io_submit_sqes() may under-consume sqes (in case of an early error)= =2E >>>>> Then it will wait for not-yet-submitted requests, deadlocking the u= ser >>>>> in most cases. >>>>> >>>>> In such cases adjust min_complete, so it won't wait for more than >>>>> what have been submitted in the current call to io_uring_enter(). I= t >>>>> may be less than totally in-flight including previous submissions, >>>>> but this shouldn't do harm and up to a user. >>>> >>>> Thanks, applied. >>> >>> This causes a behavioral change where if you ask to submit 1 but >>> there's nothing in the SQ ring, then you would get 0 before. Now >>> you get -EAGAIN. This doesn't make a lot of sense, since there's no >>> point in retrying as that won't change anything. >>> >>> Can we please just do something like the one I sent, instead of tryin= g >>> to over-complicate it? >>> >> >> Ok, when I get to a compiler. >=20 > Great, thanks. BTW, I noticed when a regression test failed. >=20 Yeah, I properly tested only the first one. Clearly, not as easy as I thought, and there were more to consider. I sent the next version, but that's odd basically taking your code. Probably, it would have been easier for you to just commit it yourself. --=20 Pavel Begunkov --6o2dx0fo4baOvOO1LsTLMrsxchoQg4tLP-- --fia9c39BoNAzl6CFYfBiYunGN9SLhccnz Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl33tSMACgkQWt5b1Glr +6WcvA//Xe9Sr6OkL35dxFzAXuY6A6E2vHGBUNdoIjJijLPZlSaGKg+GyzCEFwhw SwcU5sKdHETa1KgpI6p7flwm13N6oN9h6PNtIXUwEjdADD5F3b878k99Jb2tTezt TBarkCO6X8rPqP1I+eY6zJEYGzcNbFnJk8RkORV5q9XvM41Ph0zWd2IzBVH5MC6v Ow7I07mM7Wwg9fHGYv0DXbyyZvW2fCRBY01lfLmRiYXcygc00UzzbGO7bp+Z1gIG GVCw3es5BrqmoRta8rHD5zYGm8jgCZkrYjQJsNtutoPkOFvd1ckUqC7mT5eYfwhq ymynr3rmZ54XiVMcN8dS877JKD/CLKfjARCjGErW7iIKAYfxHijikxpkELX+wfGW aJtcNfypQABLnsW511fxl5nsl8mybNyV7oZbLvqnAo6hcjs2zBUZLv9Q247zV0Tx VIg7dw4Ep46Ng3S455Coa4O/4BD+jWKHk3qgksG3nJWMjRUJ615/LhLtedE+OYja TdqJb7qZLU91nnW3zEUYCS6kkbLtgqWvkkSabKHVHQh1ZcuwYdq6m1k1uvvltqgT J3+99HzrKqRZJKK5u6yuz/7COqdoUaADX2gRiq3Vq8sPLXSqL6/mj9vPoyEiFLtn rLEsLg9tWrjmvOn0Qij3jQcY3CH9ofbg/jwy2nc3FvW8dzMW0H0= =Z5S8 -----END PGP SIGNATURE----- --fia9c39BoNAzl6CFYfBiYunGN9SLhccnz--