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Sat, 21 Dec 2019 13:57:09 -0800 (PST) Subject: Re: [PATCH v3 2/2] io_uring: batch getting pcpu references From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: 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: <3ee072fe-e064-e1cf-cf50-a23bdfabd5d0@gmail.com> Date: Sun, 22 Dec 2019 00:56:42 +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="AFsQ35gw8k5Dqp9A1HPcRIVJ6SEYmazaE" 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) --AFsQ35gw8k5Dqp9A1HPcRIVJ6SEYmazaE Content-Type: multipart/mixed; boundary="H0UgRVQY7rhdC8t0UlnI2pFOPRpGlAfK9"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <3ee072fe-e064-e1cf-cf50-a23bdfabd5d0@gmail.com> Subject: Re: [PATCH v3 2/2] io_uring: batch getting pcpu references References: In-Reply-To: --H0UgRVQY7rhdC8t0UlnI2pFOPRpGlAfK9 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 21/12/2019 23:12, Pavel Begunkov wrote: > percpu_ref_tryget() has its own overhead. Instead getting a reference > for each request, grab a bunch once per io_submit_sqes(). >=20 > basic benchmark with submit and wait 128 non-linked nops showed ~5% > performance gain. (7044 KIOPS vs 7423) >=20 Hmm, this won't work. Please drop it. > Signed-off-by: Pavel Begunkov > --- >=20 > It's just becoming more bulky with ret for me, and would love to hear, > hot to make it clearer. This version removes all error handling from > hot path, though with goto. >=20 > fs/io_uring.c | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) >=20 > diff --git a/fs/io_uring.c b/fs/io_uring.c > index 513f1922ce6a..b89a8b975c69 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -1045,9 +1045,6 @@ static struct io_kiocb *io_get_req(struct io_ring= _ctx *ctx, > gfp_t gfp =3D GFP_KERNEL | __GFP_NOWARN; > struct io_kiocb *req; > =20 > - if (!percpu_ref_tryget(&ctx->refs)) > - return NULL; > - > if (!state) { > req =3D kmem_cache_alloc(req_cachep, gfp); > if (unlikely(!req)) > @@ -4400,6 +4397,9 @@ static int io_submit_sqes(struct io_ring_ctx *ctx= , unsigned int nr, > return -EBUSY; > } > =20 > + if (!percpu_ref_tryget_many(&ctx->refs, nr)) > + return -EAGAIN; > + > if (nr > IO_PLUG_THRESHOLD) { > io_submit_state_start(&state, nr); > statep =3D &state; > @@ -4408,16 +4408,22 @@ static int io_submit_sqes(struct io_ring_ctx *c= tx, unsigned int nr, > for (i =3D 0; i < nr; i++) { > const struct io_uring_sqe *sqe; > struct io_kiocb *req; > + unsigned int unused_refs; > =20 > req =3D io_get_req(ctx, statep); > if (unlikely(!req)) { > + unused_refs =3D nr - submitted; > if (!submitted) > submitted =3D -EAGAIN; > +put_refs: > + percpu_ref_put_many(&ctx->refs, unused_refs); > break; > } > if (!io_get_sqring(ctx, req, &sqe)) { > __io_free_req(req); > - break; > + /* __io_free_req() puts a ref */ > + unused_refs =3D nr - submitted - 1; > + goto put_refs; > } > =20 > /* will complete beyond this point, count as submitted */ >=20 --=20 Pavel Begunkov --H0UgRVQY7rhdC8t0UlnI2pFOPRpGlAfK9-- --AFsQ35gw8k5Dqp9A1HPcRIVJ6SEYmazaE Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl3+lR4ACgkQWt5b1Glr +6Xg0A//axdZrsLce8D+dVKGEl51LTsWLHfo/t5UktU4oSgfWkitlvJFepAw5YnU 7Xa/n40Y0EK4OWK9J2TpTSXQWK5V9wOtWOGnX/hw6FX0C/bnxu+ab+1fsoK23y46 0wSm0eB7Ng+1B+w48UusReUs+eKDe2G55WZQOQPziy8Yg8VW8961SyfAN1gO6oNj CplmapaI4RvkxPfvBmhnkbBBwxELLOzLUMml66ATkGAh2vsWBc31ReKYTUlKHa4l bYM8ia4BY2YedpVmSAUzS26ARUnk1GqztnIxFpRNC736T19a8MLCfV9eEWIMcy72 qb7OmAhR9r/fwv9Y0Q22jEVU1ekqaugwv8XzGmGKQRas44gMPCKcf1EsuLB/CyFN QO2rlHSoHRtmP2klX8B7T9JWR7VpfCBqXu4P5rdHOJbKQcrR8EUXYaiUC9EyeRTL wmYy3LYLk8cnRL/vpgbAohdLtlq4xlHZESHn5PKk29X5P/XfmDoS98PED4ReQehL RUrDMYLSArkz1j4N45VovFB0zVhhXDFv/g27IzjHXXiNKOxpIi1BWES8lDPmGTDX CxG6FY9dGncOE2hD6ll7u65g23KJulK2WbAu2J1RaywG9oO87FnYkmzd76ck+aQv yxmfaipUfZZldBGeonx4Lq31KMsGOYWgkVKqpfVUSL80L1T5H6c= =yMQO -----END PGP SIGNATURE----- --AFsQ35gw8k5Dqp9A1HPcRIVJ6SEYmazaE--