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=-16.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 DE862C433EF for ; Mon, 6 Sep 2021 15:35:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BB4EF61027 for ; Mon, 6 Sep 2021 15:35:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242495AbhIFPgu (ORCPT ); Mon, 6 Sep 2021 11:36:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47770 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233979AbhIFPgu (ORCPT ); Mon, 6 Sep 2021 11:36:50 -0400 Received: from mail-wr1-x42b.google.com (mail-wr1-x42b.google.com [IPv6:2a00:1450:4864:20::42b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 755ACC061575 for ; Mon, 6 Sep 2021 08:35:45 -0700 (PDT) Received: by mail-wr1-x42b.google.com with SMTP id q11so10406291wrr.9 for ; Mon, 06 Sep 2021 08:35:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=subject:from:to:cc:references:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=VTbCfTRZu3G9rHxl2HquRQKnrQMgBK/OBJLDaEqYi2I=; b=WQsodxoZkJFHCV7lhOVEKOtBwgVL/OSok0rO3OowIOHlYlgD9SMkq/CzCp5YZOgAOb XYhxrPMrVpPGN2/gK0ax7bpCS52DQhSxczzR9umBaKxB0YCYD6NtDElln/G8ZJcaA3gb q/HwQRQnvaTtIdX9YfizrETYxOf/++Khv+94M9NjDzTLKH4SlSwPxKNf9q94OIpfnJ5R qS5ztLtsnDGTSM85b8eHHBPhvxvcPMzlp3epKtGyAtlN/w2KMvnMt9NqGWyyfSZkr/vN bfF72s0OdHr6wuz8wLqCsPSTaj7CL3uBTeEvlE6fxpJhk5JejUOrEzt2+hKYujGZY93F 72CQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=VTbCfTRZu3G9rHxl2HquRQKnrQMgBK/OBJLDaEqYi2I=; b=ukarouwhREGvhm610o+lD/NmFYUHVQI/4rZgQIqEBKqS66/NJwQUErwYsYK3bvKkrK MTnWKXbX7iCzC+LwvGEA5pMCMEW4L96cFkegGTqdC62c/nAKgUGxy+aXy/5PMkUow5OM jN3rlTjp8jWc+G7tTQi1/yHz4sYZD3yWDoacBhyhb2Rciv8w6PJZBNf2QyQM+TiPJ79c tQLhVfam1YmvoFGzRWKEQOqAbFfyx5H/Q1Qtem7gR+m8FI4zr0f5g5gqTkep1DVClbIw TfElYiRexVuwW08fZnEFY0aOt10NqyL0lsU2sgWVso5mUO9ZVyA6E6gZIX9kvZey9Mms xftg== X-Gm-Message-State: AOAM531MdkTRCyN7aowlDRBFAFgtt0xKxPwux7O/IIrjEGRQTPoCaAve J05kd5PNPDFR80CDA0IoRLisOEZmdPg= X-Google-Smtp-Source: ABdhPJxTFgaeY/Wc8KVNn8A4NOefsEOaYJVeNJDbEVahKhyfgfXXAs75y0iLR8IDfRVapF3WlPvByQ== X-Received: by 2002:a5d:438a:: with SMTP id i10mr14321780wrq.285.1630942543984; Mon, 06 Sep 2021 08:35:43 -0700 (PDT) Received: from [192.168.8.197] ([148.252.133.4]) by smtp.gmail.com with ESMTPSA id z17sm8452361wrh.66.2021.09.06.08.35.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Sep 2021 08:35:30 -0700 (PDT) Subject: Re: [PATCH 5/6] io_uring: implement multishot mode for accept From: Pavel Begunkov To: Hao Xu , Jens Axboe Cc: io-uring@vger.kernel.org, Joseph Qi References: <20210903110049.132958-1-haoxu@linux.alibaba.com> <20210903110049.132958-6-haoxu@linux.alibaba.com> <3070a597-3326-5cac-253e-e2b58eebd3a2@gmail.com> <64734f7c-aaee-7ac7-752e-2d81a475d3d8@gmail.com> Message-ID: <9406066e-bfd7-4491-576f-873f4396f10d@gmail.com> Date: Mon, 6 Sep 2021 16:34:43 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <64734f7c-aaee-7ac7-752e-2d81a475d3d8@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 9/4/21 11:40 PM, Pavel Begunkov wrote: > On 9/4/21 11:39 PM, Pavel Begunkov wrote: >> On 9/3/21 12:00 PM, Hao Xu wrote: >>> Refactor io_accept() to support multishot mode. >> >> Multishot with the fixed/direct mode sounds weird (considering that >> the slot index is specified by userspace), let's forbid them. >> >> io_accept_prep() { >> if (accept->file_slot && (flags & MULTISHOT)) >> return -EINVAL; >> ... >> } > > Ah, never mind, it's already there in 6/6 btw, I think it would be less confusing if 5/6 and 6/6 are combined into a single patch. But it's a matter of taste, I guess >> >>> theoretical analysis: >>> 1) when connections come in fast >>> - singleshot: >>> add accept sqe(userpsace) --> accept inline >>> ^ | >>> |-----------------| >>> - multishot: >>> add accept sqe(userspace) --> accept inline >>> ^ | >>> |--*--| >>> >>> we do accept repeatedly in * place until get EAGAIN >>> >>> 2) when connections come in at a low pressure >>> similar thing like 1), we reduce a lot of userspace-kernel context >>> switch and useless vfs_poll() >>> >>> tests: >>> Did some tests, which goes in this way: >>> >>> server client(multiple) >>> accept connect >>> read write >>> write read >>> close close >>> >>> Basically, raise up a number of clients(on same machine with server) to >>> connect to the server, and then write some data to it, the server will >>> write those data back to the client after it receives them, and then >>> close the connection after write return. Then the client will read the >>> data and then close the connection. Here I test 10000 clients connect >>> one server, data size 128 bytes. And each client has a go routine for >>> it, so they come to the server in short time. >>> test 20 times before/after this patchset, time spent:(unit cycle, which >>> is the return value of clock()) >>> before: >>> 1930136+1940725+1907981+1947601+1923812+1928226+1911087+1905897+1941075 >>> +1934374+1906614+1912504+1949110+1908790+1909951+1941672+1969525+1934984 >>> +1934226+1914385)/20.0 = 1927633.75 >>> after: >>> 1858905+1917104+1895455+1963963+1892706+1889208+1874175+1904753+1874112 >>> +1874985+1882706+1884642+1864694+1906508+1916150+1924250+1869060+1889506 >>> +1871324+1940803)/20.0 = 1894750.45 >>> >>> (1927633.75 - 1894750.45) / 1927633.75 = 1.65% >>> >>> Signed-off-by: Hao Xu >>> --- >>> >>> not sure if we should cancel it when io_cqring_fill_event() reurn false >>> >>> fs/io_uring.c | 34 +++++++++++++++++++++++++++++----- >>> 1 file changed, 29 insertions(+), 5 deletions(-) >>> >>> diff --git a/fs/io_uring.c b/fs/io_uring.c >>> index dae7044e0c24..eb81d37dce78 100644 >>> --- a/fs/io_uring.c >>> +++ b/fs/io_uring.c >>> @@ -4885,16 +4885,18 @@ static int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) >>> >>> static int io_accept(struct io_kiocb *req, unsigned int issue_flags) >>> { >>> + struct io_ring_ctx *ctx = req->ctx; >>> struct io_accept *accept = &req->accept; >>> bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK; >>> unsigned int file_flags = force_nonblock ? O_NONBLOCK : 0; >>> bool fixed = !!accept->file_slot; >>> struct file *file; >>> - int ret, fd; >>> + int ret, ret2 = 0, fd; >>> >>> if (req->file->f_flags & O_NONBLOCK) >>> req->flags |= REQ_F_NOWAIT; >>> >>> +retry: >>> if (!fixed) { >>> fd = __get_unused_fd_flags(accept->flags, accept->nofile); >>> if (unlikely(fd < 0)) >>> @@ -4906,20 +4908,42 @@ static int io_accept(struct io_kiocb *req, unsigned int issue_flags) >>> if (!fixed) >>> put_unused_fd(fd); >>> ret = PTR_ERR(file); >>> - if (ret == -EAGAIN && force_nonblock) >>> - return -EAGAIN; >>> + if (ret == -EAGAIN && force_nonblock) { >>> + if ((req->flags & (REQ_F_APOLL_MULTISHOT | REQ_F_POLLED)) == >>> + (REQ_F_APOLL_MULTISHOT | REQ_F_POLLED)) >>> + ret = 0; >>> + return ret; >>> + } >>> if (ret == -ERESTARTSYS) >>> ret = -EINTR; >>> req_set_fail(req); >>> } else if (!fixed) { >>> fd_install(fd, file); >>> ret = fd; >>> + /* >>> + * if it's in multishot mode, let's return -EAGAIN to make it go >>> + * into fast poll path >>> + */ >>> + if ((req->flags & REQ_F_APOLL_MULTISHOT) && force_nonblock && >>> + !(req->flags & REQ_F_POLLED)) >>> + ret2 = -EAGAIN; >>> } else { >>> ret = io_install_fixed_file(req, file, issue_flags, >>> accept->file_slot - 1); >>> } >>> - __io_req_complete(req, issue_flags, ret, 0); >>> - return 0; >>> + >>> + if (req->flags & REQ_F_APOLL_MULTISHOT) { >>> + spin_lock(&ctx->completion_lock); >>> + if (io_cqring_fill_event(ctx, req->user_data, ret, 0)) { >>> + io_commit_cqring(ctx); >>> + ctx->cq_extra++; >>> + } >>> + spin_unlock(&ctx->completion_lock); >>> + goto retry; >>> + } else { >>> + __io_req_complete(req, issue_flags, ret, 0); >>> + } >>> + return ret2; >>> } >>> >>> static int io_connect_prep_async(struct io_kiocb *req) >>> >> > -- Pavel Begunkov