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Mon, 23 Mar 2020 01:39:04 -0700 (PDT) Received: from [192.168.43.123] ([109.126.140.227]) by smtp.gmail.com with ESMTPSA id h81sm22594097wme.42.2020.03.23.01.39.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Mar 2020 01:39:04 -0700 (PDT) To: Jens Axboe , io-uring References: <3454f8c1-3d5a-1f94-569a-41e553fc836a@gmail.com> 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 v2] io-wq: handle hashed writes in chains Message-ID: Date: Mon, 23 Mar 2020 11:38:04 +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: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="FxI1HWLB8ulzcMhZg69xpg6CLnPQzK1eF" 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) --FxI1HWLB8ulzcMhZg69xpg6CLnPQzK1eF Content-Type: multipart/mixed; boundary="FfD6x6MiB5WKzp90CkbymDzPbJ4wtjM14"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , io-uring Message-ID: Subject: Re: [PATCH v2] io-wq: handle hashed writes in chains References: <3454f8c1-3d5a-1f94-569a-41e553fc836a@gmail.com> In-Reply-To: --FfD6x6MiB5WKzp90CkbymDzPbJ4wtjM14 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 23/03/2020 04:37, Jens Axboe wrote: > On 3/22/20 2:25 PM, Pavel Begunkov wrote: >> On 22/03/2020 22:51, Jens Axboe wrote: >>> commit f1d96a8fcbbbb22d4fbc1d69eaaa678bbb0ff6e2 >>> Author: Pavel Begunkov >>> Date: Fri Mar 13 22:29:14 2020 +0300 >>> >>> io_uring: NULL-deref for IOSQE_{ASYNC,DRAIN} >>> >>> which is what I ran into as well last week... >> >> I picked it before testing >> >>> The extra memory isn't a bit deal, it's very minor. My main concern >>> would be fairness, since we'd then be grabbing non-contig hashed chun= ks, >>> before we did not. May not be a concern as long as we ensure the >>> non-hasned (and differently hashed) work can proceed in parallel. For= my >>> end, I deliberately added: >> >> Don't think it's really a problem, all ordering/scheduling is up to >> users (i.e. io_uring), and it can't infinitely postpone a work, >> because it's processing spliced requests without taking more, even if >> new ones hash to the same bit. >=20 > I don't disagree with you, just wanted to bring it up! Sure, there is a lot to think about. E.g. I don't like this reenqueueing,= and if all other thread have enough work to do, then it can avoided, but = don't want to over-complicate. >=20 >>> + /* already have hashed work, let new worker get this */ >>> + if (ret) { >>> + struct io_wqe_acct *acct; >>> + >>> + /* get new worker for unhashed, if none now */ >>> + acct =3D io_work_get_acct(wqe, work); >>> + if (!atomic_read(&acct->nr_running)) >>> + io_wqe_wake_worker(wqe, acct); >>> + break; >>> + } >>> >>> to try and improve that. >> >> Is there performance problems with your patch without this chunk? I >> may see another problem with yours, I need to think it through. >=20 > No, and in fact it probably should be a separate thing, but I kind of > like your approach so not moving forward with mine. I do think it's > worth looking into separately, as there's no reason why we can't wake a= > non-hashed worker if we're just doing hashed work from the existing > thread. If that thread is just doing copies and not blocking, the > unhashed (or next hashed) work is just sitting idle while it could be > running instead. Then, I'll clean the diff, hopefully soon. Could I steal parts of your pa= tch description? >=20 > Hence I added that hunk, to kick a new worker to proceed in parallel. It seems, I need to take a closer look at this accounting in general. --=20 Pavel Begunkov --FfD6x6MiB5WKzp90CkbymDzPbJ4wtjM14-- --FxI1HWLB8ulzcMhZg69xpg6CLnPQzK1eF Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl54dXMACgkQWt5b1Glr +6XOMBAAhsLkIqBK1we2IWHCbK99MwN93jd+RXuBMIKZtDIRKHW5+0el6CaULzNm OX5lwDZDWsDlbeoIxj6lHIukuUUU2gGoeQHlDwHO5CatRPq5L98LCgBd+qxei0Bv fwgRk/Dfzr+/anct3sRhp5lzYIVXSrEhb34DRzlFT7omm7qgeq4RexE1eqxb+gWL D+wVhvJsQOHUC/HlXWYNFBmhHQGzaJKGOLXEzWeXbN7pLH1GBJnD+EVwbCPq5gp7 XI/N0QEXyjDzAjmlOfbcqrQ5lz9Ouu3QCRBCXGeHzmHxBA9jGzD9YA6j8DjlokgI oCl9O/LtJ9sbxSK9VvS9ornqb+ieD4ux4t6GcfzvyDJRw9Vd6QSWdGp3TINGFxKM pWMd1fXPLAgKK6m+NeZtm7kK0Z3R7ER7HshW8fbmtUwKH+KwqsBjg3A1TzPliLvo KlduziSYgaHuZ+viIdnMjMQskS41WJSAMM4li+76sNhFCDzCHE5g7/oGKel0avBH +iqBi4sX3g+37YZPVfmVSfjaBza0Q+IhKJR5ROm+o1GE68HxDoV1T8A7ECjGA21A bIKgyhAVNP88Rt/GsdY62Tx7l8GW2pZOyrK+z8W5qq6wPGt/vk1jREG+/Lg0eM07 rgijyaCvuFA1d6mdaXWKJP7GtnvUujBDxN+UQZLkoQiy+J5kHqE= =MIPX -----END PGP SIGNATURE----- --FxI1HWLB8ulzcMhZg69xpg6CLnPQzK1eF--