From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88BF4C35DEA for ; Tue, 25 Feb 2020 00:40:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 551F92072D for ; Tue, 25 Feb 2020 00:40:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="JD72/O4U" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728316AbgBYAkA (ORCPT ); Mon, 24 Feb 2020 19:40:00 -0500 Received: from mail-wr1-f66.google.com ([209.85.221.66]:45826 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728011AbgBYAj7 (ORCPT ); Mon, 24 Feb 2020 19:39:59 -0500 Received: by mail-wr1-f66.google.com with SMTP id g3so12584349wrs.12 for ; Mon, 24 Feb 2020 16:39:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=to:from:autocrypt:subject:message-id:date:user-agent:mime-version :content-language:content-transfer-encoding; bh=M6b+yUjkrxpk2X0AVYMdHP/LxGDwuHV9SwPNp0wPrL8=; b=JD72/O4Uc7zX8/XF6iad8fSjs91PrAy3Bu0AynBEIKNAqd7VMmBVYbTIbpg7qM8WXG BMO7ODG9tqz0UhLlcS+HbN0pr2r/XqdsDrMQm/7f50bAm17PCm+3go/9Y78+GP5q3J+G YWDW3iFhThru6zOoQY3yoJNM/+zmSZV533r5h2dDcPgzPB+IH/9yklSbUmnWa4dJ6+BT IIWQ0wtQjdsLaDbaEU7XyD6+V6ypR25efzRjf3N/AFlVK5DzgJ9dOJ88idoc4hZmTZhZ H2YABaz/Fjf8a1nX9f+8LVqIo+bd3ALpG5VszfnikMT8bqoZTIRgAWUM0UJ7PzdrhFST pg/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:from:autocrypt:subject:message-id:date :user-agent:mime-version:content-language:content-transfer-encoding; bh=M6b+yUjkrxpk2X0AVYMdHP/LxGDwuHV9SwPNp0wPrL8=; b=Rq5z421FhIM1d2WxruXgNNiDh3D2Tn6Hv0fwH1z0pDzll2Bf7ROLxzvltFMkMZZUkA iE+lY/bcPNe08lz3ER4HrW2/KYhrk76F2jM16k5u7KToyftY6aQZfSChXu69YhMOMoSQ 4IqdKmQGmlZfmvxwhTG0fiXZVuFZH9YMt6s6JfTBgl25PBmJFw935dxiuWb8hOVm4pbL Gvh+MRB3MXWVsSY9E6G9T7c2ocSfcPIkguD8d8PnvCYoR3b+B4HLQW7rcqcqJKe1Vf12 VOKyerQRIVOmZWiKMFqX0D5YE1X7tJmGUOnCEdnGqgiYIRCHP6HC+t9ifLSrl5aRIhxs 73jA== X-Gm-Message-State: APjAAAUskYDrhR3hBXMWkGWuv9euUzHV9NeaKWWghnvGBrc0+O5Of7r7 BmPzw6SKGAMiekPu/JJudge8YL4V X-Google-Smtp-Source: APXvYqyuVXyJhaP4fMV6veIi0xM5zTdgYyz/fN0RLp3lTbNPVxLLSNduNtX7tZQPvObGzHK8DAlnVg== X-Received: by 2002:a5d:5188:: with SMTP id k8mr69402462wrv.151.1582591197089; Mon, 24 Feb 2020 16:39:57 -0800 (PST) Received: from [192.168.43.206] ([109.126.137.65]) by smtp.gmail.com with ESMTPSA id c26sm1264447wmb.8.2020.02.24.16.39.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Feb 2020 16:39:56 -0800 (PST) To: Jens Axboe , io-uring , =?UTF-8?B?5p2O6YCa5rSy?= 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: [RFC] single cqe per link Message-ID: <1a9a6022-7175-8ed3-4668-e4de3a2b9ff7@gmail.com> Date: Tue, 25 Feb 2020 03:39:11 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org I've got curious about performance of the idea of having only 1 CQE per link (for the failed or last one). Tested it with a quick dirty patch doing submit-and-reap of a nops-link (patched for inline execution). 1) link size: 100 old: 206 ns per nop new: 144 ns per nop 2) link size: 10 old: 234 ns per nop new: 181 ns per nop 3) link size: 10, FORCE_ASYNC old: 667 ns per nop new: 569 ns per nop The patch below breaks sequences, linked_timeout and who knows what else. The first one requires synchronisation/atomic, so it's a bit in the way. I've been wondering, whether IOSQE_IO_DRAIN is popular and how much it's used. We can try to find tradeoff or even disable it with this feature. diff --git a/fs/io_uring.c b/fs/io_uring.c index 65a61b8b37c4..9ec29f01cfda 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1164,7 +1164,7 @@ static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force) return cqe != NULL; } -static void io_cqring_fill_event(struct io_kiocb *req, long res) +static void __io_cqring_fill_event(struct io_kiocb *req, long res) { struct io_ring_ctx *ctx = req->ctx; struct io_uring_cqe *cqe; @@ -1196,13 +1196,31 @@ static void io_cqring_fill_event(struct io_kiocb *req, long res) } } +static inline bool io_ignore_cqe(struct io_kiocb *req) +{ + if (!(req->ctx->flags & IORING_SETUP_BOXED_CQE)) + return false; + + return (req->flags & (REQ_F_LINK|REQ_F_FAIL_LINK)) == REQ_F_LINK; +} + +static void io_cqring_fill_event(struct io_kiocb *req, long res) +{ + if (io_ignore_cqe(req)) + return; + __io_cqring_fill_event(req, res); +} + static void io_cqring_add_event(struct io_kiocb *req, long res) { struct io_ring_ctx *ctx = req->ctx; unsigned long flags; + if (io_ignore_cqe(req)) + return; + spin_lock_irqsave(&ctx->completion_lock, flags); - io_cqring_fill_event(req, res); + __io_cqring_fill_event(req, res); io_commit_cqring(ctx); spin_unlock_irqrestore(&ctx->completion_lock, flags); @@ -7084,7 +7102,8 @@ static long io_uring_setup(u32 entries, struct io_uring_params __user *params) if (p.flags & ~(IORING_SETUP_IOPOLL | IORING_SETUP_SQPOLL | IORING_SETUP_SQ_AFF | IORING_SETUP_CQSIZE | - IORING_SETUP_CLAMP | IORING_SETUP_ATTACH_WQ)) + IORING_SETUP_CLAMP | IORING_SETUP_ATTACH_WQ | + IORING_SETUP_BOXED_CQE)) return -EINVAL; ret = io_uring_create(entries, &p); diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index 08891cc1c1e7..3d69369e252c 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -86,6 +86,7 @@ enum { #define IORING_SETUP_CQSIZE (1U << 3) /* app defines CQ size */ #define IORING_SETUP_CLAMP (1U << 4) /* clamp SQ/CQ ring sizes */ #define IORING_SETUP_ATTACH_WQ (1U << 5) /* attach to existing wq */ +#define IORING_SETUP_BOXED_CQE (1U << 6) /* single sqe per link */ enum { IORING_OP_NOP, -- Pavel Begunkov