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Sat, 28 Dec 2019 03:16:22 -0800 (PST) Subject: Re: [PATCH v4 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: <1250dad37e9b73d39066a8b464f6d2cab26eef8a.1577528535.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: <6facf552-924f-2af1-03e5-99957a90bfd0@gmail.com> Date: Sat, 28 Dec 2019 14:15:54 +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: <1250dad37e9b73d39066a8b464f6d2cab26eef8a.1577528535.git.asml.silence@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/12/2019 14:13, 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(). > > ~5% throughput boost for a "submit and wait 128 nops" benchmark. > > Signed-off-by: Pavel Begunkov > --- > fs/io_uring.c | 26 +++++++++++++++++--------- > 1 file changed, 17 insertions(+), 9 deletions(-) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index 7fc1158bf9a4..404946080e86 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -1080,9 +1080,6 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx, > gfp_t gfp = GFP_KERNEL | __GFP_NOWARN; > struct io_kiocb *req; > > - if (!percpu_ref_tryget(&ctx->refs)) > - return NULL; > - > if (!state) { > req = kmem_cache_alloc(req_cachep, gfp); > if (unlikely(!req)) > @@ -1141,6 +1138,14 @@ static void io_free_req_many(struct io_ring_ctx *ctx, void **reqs, int *nr) > } > } > > +static void __io_req_free_empty(struct io_kiocb *req) If anybody have better naming (or a better approach at all), I'm all ears. > +{ > + if (likely(!io_is_fallback_req(req))) > + kmem_cache_free(req_cachep, req); > + else > + clear_bit_unlock(0, (unsigned long *) req->ctx->fallback_req); > +} > + > static void __io_free_req(struct io_kiocb *req) > { > struct io_ring_ctx *ctx = req->ctx; > @@ -1162,11 +1167,9 @@ static void __io_free_req(struct io_kiocb *req) > wake_up(&ctx->inflight_wait); > spin_unlock_irqrestore(&ctx->inflight_lock, flags); > } > - percpu_ref_put(&ctx->refs); > - if (likely(!io_is_fallback_req(req))) > - kmem_cache_free(req_cachep, req); > - else > - clear_bit_unlock(0, (unsigned long *) ctx->fallback_req); > + > + percpu_ref_put(&req->ctx->refs); > + __io_req_free_empty(req); > } > > static bool io_link_cancel_timeout(struct io_kiocb *req) > @@ -4551,6 +4554,9 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr, > return -EBUSY; > } > > + if (!percpu_ref_tryget_many(&ctx->refs, nr)) > + return -EAGAIN; > + > if (nr > IO_PLUG_THRESHOLD) { > io_submit_state_start(&state, nr); > statep = &state; > @@ -4567,7 +4573,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr, > break; > } > if (!io_get_sqring(ctx, req, &sqe)) { > - __io_free_req(req); > + __io_req_free_empty(req); > break; > } > > @@ -4598,6 +4604,8 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr, > break; > } > > + if (submitted != nr) > + percpu_ref_put_many(&ctx->refs, nr - submitted); > if (link) > io_queue_link_head(link); > if (statep) > -- Pavel Begunkov