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Sat, 21 Dec 2019 08:20:56 -0800 (PST) Subject: Re: [PATCH RFC v2 3/3] io_uring: batch get(ctx->ref) across submits From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Tejun Heo , Dennis Zhou , Christoph Lameter References: <925d8fe5406779bbfa108caa3d1f9fd16e3434b5.1576944502.git.asml.silence@gmail.com> 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: Date: Sat, 21 Dec 2019 19:20:26 +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: <925d8fe5406779bbfa108caa3d1f9fd16e3434b5.1576944502.git.asml.silence@gmail.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="ow1cDVrtXZKifTO9wYjzMLzoVJkGTwjAe" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --ow1cDVrtXZKifTO9wYjzMLzoVJkGTwjAe Content-Type: multipart/mixed; boundary="W2cy8CHM4527v9y7P13rqyRDRYLtYYsmD"; protected-headers="v1" From: Pavel Begunkov To: Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Tejun Heo , Dennis Zhou , Christoph Lameter Message-ID: Subject: Re: [PATCH RFC v2 3/3] io_uring: batch get(ctx->ref) across submits References: <925d8fe5406779bbfa108caa3d1f9fd16e3434b5.1576944502.git.asml.silence@gmail.com> In-Reply-To: <925d8fe5406779bbfa108caa3d1f9fd16e3434b5.1576944502.git.asml.silence@gmail.com> --W2cy8CHM4527v9y7P13rqyRDRYLtYYsmD Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 21/12/2019 19:15, Pavel Begunkov wrote: > Double account ctx->refs keeping number of taken refs in ctx. As > io_uring gets per-request ctx->refs during submission, while holding > ctx->uring_lock, this allows in most of the time to bypass > percpu_ref_get*() and its overhead. Jens, could you please benchmark with this one? Especially for offloaded = QD1 case. I haven't got any difference for nops test and don't have a decent = SSD at hands to test it myself. We could drop it, if there is no benefit. This rewrites that @extra_refs from the second one, so I left it for now.= >=20 > Signed-off-by: Pavel Begunkov > --- > fs/io_uring.c | 32 +++++++++++++++++++++++++------- > 1 file changed, 25 insertions(+), 7 deletions(-) >=20 > diff --git a/fs/io_uring.c b/fs/io_uring.c > index 5392134f042f..eef09de94609 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -84,6 +84,9 @@ > #define IORING_MAX_ENTRIES 32768 > #define IORING_MAX_CQ_ENTRIES (2 * IORING_MAX_ENTRIES) > =20 > +/* Not less than IORING_MAX_ENTRIES, so can grab once per submission l= oop */ > +#define IORING_REFS_THRESHOLD IORING_MAX_ENTRIES > + > /* > * Shift of 9 is 512 entries, or exactly one page on 64-bit archs > */ > @@ -197,6 +200,7 @@ struct fixed_file_data { > struct io_ring_ctx { > struct { > struct percpu_ref refs; > + unsigned long taken_refs; /* used under @uring_lock */ > } ____cacheline_aligned_in_smp; > =20 > struct { > @@ -690,6 +694,13 @@ static void io_ring_ctx_ref_free(struct percpu_ref= *ref) > complete(&ctx->completions[0]); > } > =20 > +static void io_free_taken_refs(struct io_ring_ctx *ctx) > +{ > + if (ctx->taken_refs) > + percpu_ref_put_many(&ctx->refs, ctx->taken_refs); > + ctx->taken_refs =3D 0; > +} > + > static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p= ) > { > struct io_ring_ctx *ctx; > @@ -4388,7 +4399,6 @@ static int io_submit_sqes(struct io_ring_ctx *ctx= , unsigned int nr, > struct io_submit_state state, *statep =3D NULL; > struct io_kiocb *link =3D NULL; > int i, submitted =3D 0; > - unsigned int extra_refs; > bool mm_fault =3D false; > =20 > /* if we have a backlog and couldn't flush it all, return BUSY */ > @@ -4398,9 +4408,15 @@ static int io_submit_sqes(struct io_ring_ctx *ct= x, unsigned int nr, > return -EBUSY; > } > =20 > - if (!percpu_ref_tryget_many(&ctx->refs, nr)) > - return -EAGAIN; > - extra_refs =3D nr; > + if (ctx->taken_refs < IORING_REFS_THRESHOLD) { > + if (unlikely(percpu_ref_is_dying(&ctx->refs))) { > + io_free_taken_refs(ctx); > + return -ENXIO; > + } > + if (!percpu_ref_tryget_many(&ctx->refs, IORING_REFS_THRESHOLD)) > + return -EAGAIN; > + ctx->taken_refs +=3D IORING_REFS_THRESHOLD; > + } > =20 > if (nr > IO_PLUG_THRESHOLD) { > io_submit_state_start(&state, nr); > @@ -4417,8 +4433,9 @@ static int io_submit_sqes(struct io_ring_ctx *ctx= , unsigned int nr, > submitted =3D -EAGAIN; > break; > } > - --extra_refs; > if (!io_get_sqring(ctx, req, &sqe)) { > + /* not submitted, but a ref is freed */ > + ctx->taken_refs--; > __io_free_req(req); > break; > } > @@ -4454,8 +4471,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx= , unsigned int nr, > io_queue_link_head(link); > if (statep) > io_submit_state_end(&state); > - if (extra_refs) > - percpu_ref_put_many(&ctx->refs, extra_refs); > + ctx->taken_refs -=3D submitted; > =20 > /* Commit SQ ring head once we've consumed and submitted all SQEs */= > io_commit_sqring(ctx); > @@ -5731,6 +5747,7 @@ static int io_uring_fasync(int fd, struct file *f= ile, int on) > static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx) > { > mutex_lock(&ctx->uring_lock); > + io_free_taken_refs(ctx); > percpu_ref_kill(&ctx->refs); > mutex_unlock(&ctx->uring_lock); > =20 > @@ -6196,6 +6213,7 @@ static int __io_uring_register(struct io_ring_ctx= *ctx, unsigned opcode, > =20 > if (opcode !=3D IORING_UNREGISTER_FILES && > opcode !=3D IORING_REGISTER_FILES_UPDATE) { > + io_free_taken_refs(ctx); > percpu_ref_kill(&ctx->refs); > =20 > /* >=20 --=20 Pavel Begunkov --W2cy8CHM4527v9y7P13rqyRDRYLtYYsmD-- --ow1cDVrtXZKifTO9wYjzMLzoVJkGTwjAe 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+Rk0ACgkQWt5b1Glr +6V/Wg//cNJRnigCPb609gdMvttE89kiqQAiHdLiPBObgLLi6kGoV+6j0Cfu5FhN aUnd4fKVJ5NXVEDdwSTnMgy7rqM33TnT7Q/MWnnkxxfNFI7JYrXSdxlCZeANsbsm vhJ/bmFSOKkbuKkLe9yN9LcJZabIiU5LTyp0UyIbEwD06e0Sp0EU98wZQ+XBxfB7 gOMNDVO1Jk2U0+yJqrqUXQ6Mam5XDrcb+qsUXPvGCMc46fobJyp75x+LHftdtsga XDLT32OAPLh0snFL6VYgow3D0Luko6TCztFM3nIcSxYQFzelK/Lf0+94k3cyssfG nKIUirWIMG/Nv69m8Zg19LxZiqlSStma+nYliFFS0lZYpsTIO3c/RfiEnNKpJOlI gl/rbyoox8Z1r0enZbtW9M7mLt23pKZ0Seu2AZ5dRs874sBNv0ZyVh9jvWRCFOFb SYX88/EDVJ4hK9HQk7dB26B30dbd0WYaljg8aypWuvWb59f4mZ9lPleI6AowZ1UM YuPi5wbIL8XML3O21A0MqZSx8BC37ztCGqnSGEEgy6Ooz9UjT2wcvdnuUQnd8MGK g6mR5xxUgSbmJDD7YZ0QIYztwfan5T1jk7ZwPBGFTT0w+EBBY2CwM9FfmxSVODcc 61sdN4JYx9sIOt2JX33lJqZc+an+IAJIuIE3GE+B2CluVS3SvMs= =kJHm -----END PGP SIGNATURE----- --ow1cDVrtXZKifTO9wYjzMLzoVJkGTwjAe--