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 AA26DC433F5 for ; Mon, 6 Sep 2021 15:57:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 92CC760F6B for ; Mon, 6 Sep 2021 15:57:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243542AbhIFP6K (ORCPT ); Mon, 6 Sep 2021 11:58:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231591AbhIFP6J (ORCPT ); Mon, 6 Sep 2021 11:58:09 -0400 Received: from mail-wr1-x433.google.com (mail-wr1-x433.google.com [IPv6:2a00:1450:4864:20::433]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7A74EC061575 for ; Mon, 6 Sep 2021 08:57:04 -0700 (PDT) Received: by mail-wr1-x433.google.com with SMTP id i6so10513026wrv.2 for ; Mon, 06 Sep 2021 08:57:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=to:cc:references:from:subject:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=pgyrLlMnQZ+O22RVx7ecH7laHegZPTWxrJzxqIDUuTY=; b=mCvGfcdnAHTrjIKLoD5mrunMFQpkuBjb8f06hy1fS+djv+0QCED6eJFujH/2es9qxU rxc9CsU62mQ08/cexl/DPUCSe9QEh9gSfC5vXfqI0HJ5pxtQ7AXKhldoSplLTCIxdKWf 6hala8iG2faskcvPKBxxC3LzKC1E5XkZXWECoMJDiQflKK0IeCc2NRhMzcqQzLCh0I6T dGdx/QG6yRrAKysv8HVOHzQ0kPpeIjmdsS0o2VxTnoHnGgYySNm7WRUUigDcBKI4u2vs vNwBYq2dtvy809urU5e1qyw1bNCuUF9sNLmT8Bc5l4cZqMq9rTHQz70ql05riF870PKi HicA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:to:cc:references:from:subject:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=pgyrLlMnQZ+O22RVx7ecH7laHegZPTWxrJzxqIDUuTY=; b=bflNJiocKeQg3pYNuThH92griiawBGqMlV0oNyPA0PMtnRYoPcdIFC8+de2B56EfxA 3RU1iTKX0wiIuKG0yU3S6dmFb3V8KQNWpAoFpef2YT+ZPiZ7HuojWF5lO9ZPytE5Ycbs 6FHUAib/aVQ8xwwtOF9M/FRa8R5WXRRhvN3Op7ODt/JSV4oGyDTVu8kDY5mQs5Q+HVEf 6XzuEM4eCTqIr5NSL7jahfC1XvqLupGINC4rkB07jk5BXddXC0ljDCDJieRI5ekRoAVY dBNVoRj5Cd0fLWDF4abfcMVOwf1WF4IUaj/YIyq3ES2VDvF4KnQWMzYEOl2eIuMbEHPX K1Nw== X-Gm-Message-State: AOAM532iSyxcjXM1s9Bc/5X834KZeTLPYs3iY3rq0qjawrEGr+/zt7HK ppGJdFz1OqbGHidYj/J56uI= X-Google-Smtp-Source: ABdhPJwRJ8M+iyDHy1m+BkKqEs9peEEMT/hFQLxHNpsI7Kzc+b36nSvcmgzNvnvAZGqoUUJNSB8xEQ== X-Received: by 2002:adf:f0c7:: with SMTP id x7mr13202207wro.42.1630943823142; Mon, 06 Sep 2021 08:57:03 -0700 (PDT) Received: from [192.168.8.197] ([148.252.133.4]) by smtp.gmail.com with ESMTPSA id z5sm1836739wmf.33.2021.09.06.08.57.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Sep 2021 08:57:02 -0700 (PDT) To: Hao Xu , Jens Axboe Cc: io-uring@vger.kernel.org, Joseph Qi References: <20210903110049.132958-1-haoxu@linux.alibaba.com> <20210903110049.132958-5-haoxu@linux.alibaba.com> From: Pavel Begunkov Subject: Re: [PATCH 4/6] io_uring: let fast poll support multishot Message-ID: Date: Mon, 6 Sep 2021 16:56:29 +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: <20210903110049.132958-5-haoxu@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 9/3/21 12:00 PM, Hao Xu wrote: > For operations like accept, multishot is a useful feature, since we can > reduce a number of accept sqe. Let's integrate it to fast poll, it may > be good for other operations in the future. __io_arm_poll_handler() | -> vfs_poll() | | io_async_task_func() // post CQE | ... | do_apoll_rewait(); -> continues after vfs_poll(),| removing poll->head of | the second poll attempt. | One of the reasons for forbidding multiple apoll's is that it might be racy. I haven't looked into this implementation, but we should check if there will be problems from that. FWIW, putting aside this patchset, the poll/apoll is not in the best shape and can use some refactoring. > Signed-off-by: Hao Xu > --- > fs/io_uring.c | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index d6df60c4cdb9..dae7044e0c24 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -5277,8 +5277,15 @@ static void io_async_task_func(struct io_kiocb *req, bool *locked) > return; > } > > - hash_del(&req->hash_node); > - io_poll_remove_double(req); > + if (READ_ONCE(apoll->poll.canceled)) > + apoll->poll.events |= EPOLLONESHOT; > + if (apoll->poll.events & EPOLLONESHOT) { > + hash_del(&req->hash_node); > + io_poll_remove_double(req); > + } else { > + add_wait_queue(apoll->poll.head, &apoll->poll.wait); > + } > + > spin_unlock(&ctx->completion_lock); > > if (!READ_ONCE(apoll->poll.canceled)) > @@ -5366,7 +5373,7 @@ static int io_arm_poll_handler(struct io_kiocb *req) > struct io_ring_ctx *ctx = req->ctx; > struct async_poll *apoll; > struct io_poll_table ipt; > - __poll_t ret, mask = EPOLLONESHOT | POLLERR | POLLPRI; > + __poll_t ret, mask = POLLERR | POLLPRI; > int rw; > > if (!req->file || !file_can_poll(req->file)) > @@ -5388,6 +5395,8 @@ static int io_arm_poll_handler(struct io_kiocb *req) > rw = WRITE; > mask |= POLLOUT | POLLWRNORM; > } > + if (!(req->flags & REQ_F_APOLL_MULTISHOT)) > + mask |= EPOLLONESHOT; > > /* if we can't nonblock try, then no point in arming a poll handler */ > if (!io_file_supports_nowait(req, rw)) > -- Pavel Begunkov