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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3E70AC433F5 for ; Mon, 11 Oct 2021 08:55:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2541A60F43 for ; Mon, 11 Oct 2021 08:55:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235308AbhJKI5I (ORCPT ); Mon, 11 Oct 2021 04:57:08 -0400 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:50620 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235163AbhJKI5H (ORCPT ); Mon, 11 Oct 2021 04:57:07 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R971e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04357;MF=haoxu@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0UrOCGrW_1633942505; Received: from B-25KNML85-0107.local(mailfrom:haoxu@linux.alibaba.com fp:SMTPD_---0UrOCGrW_1633942505) by smtp.aliyun-inc.com(127.0.0.1); Mon, 11 Oct 2021 16:55:06 +0800 Subject: Re: [PATCH 2/2] io_uring: implementation of IOSQE_ASYNC_HYBRID logic To: Pavel Begunkov , Jens Axboe Cc: io-uring@vger.kernel.org, Joseph Qi References: <20211008123642.229338-1-haoxu@linux.alibaba.com> <20211008123642.229338-3-haoxu@linux.alibaba.com> <0c0f713e-f1ef-5798-f38f-18ef8358eb6b@gmail.com> From: Hao Xu Message-ID: Date: Mon, 11 Oct 2021 16:55:05 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <0c0f713e-f1ef-5798-f38f-18ef8358eb6b@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org 在 2021/10/9 下午8:46, Pavel Begunkov 写道: > On 10/8/21 13:36, Hao Xu wrote: >> The process of this kind of requests is: >> >> step1: original context: >>             queue it to io-worker >> step2: io-worker context: >>             nonblock try(the old logic is a synchronous try here) >>                 | >>                 |--fail--> arm poll >>                              | >>                              |--(fail/ready)-->synchronous issue >>                              | >>                              |--(succeed)-->worker finish it's job, tw >>                                             take over the req >> >> This works much better than IOSQE_ASYNC in cases where cpu resources >> are scarce or unbound max_worker is small. In these cases, number of >> io-worker eazily increments to max_worker, new worker cannot be created >> and running workers stuck there handling old works in IOSQE_ASYNC mode. >> >> In my machine, set unbound max_worker to 20, run echo-server, turns out: >> (arguments: register_file, connetion number is 1000, message size is 12 >> Byte) >> IOSQE_ASYNC: 76664.151 tps >> IOSQE_ASYNC_HYBRID: 166934.985 tps >> >> Suggested-by: Jens Axboe >> Signed-off-by: Hao Xu >> --- >>   fs/io_uring.c | 42 ++++++++++++++++++++++++++++++++++++++---- >>   1 file changed, 38 insertions(+), 4 deletions(-) >> >> diff --git a/fs/io_uring.c b/fs/io_uring.c >> index a99f7f46e6d4..024cef09bc12 100644 >> --- a/fs/io_uring.c >> +++ b/fs/io_uring.c >> @@ -1409,7 +1409,7 @@ static void io_prep_async_work(struct io_kiocb >> *req) >>       req->work.list.next = NULL; >>       req->work.flags = 0; >> -    if (req->flags & REQ_F_FORCE_ASYNC) >> +    if (req->flags & (REQ_F_FORCE_ASYNC | REQ_F_ASYNC_HYBRID)) >>           req->work.flags |= IO_WQ_WORK_CONCURRENT; >>       if (req->flags & REQ_F_ISREG) { >> @@ -5575,7 +5575,13 @@ static int io_arm_poll_handler(struct io_kiocb >> *req) >>       req->apoll = apoll; >>       req->flags |= REQ_F_POLLED; >>       ipt.pt._qproc = io_async_queue_proc; >> -    io_req_set_refcount(req); >> +    /* >> +     * REQ_F_REFCOUNT set indicate we are in io-worker context, where we > > Nope, it indicates that needs more complex refcounting. It includes linked > timeouts but also poll because of req_ref_get for double poll. fwiw, with > some work it can be removed for polls, harder (and IMHO not necessary) > to do > for timeouts.Agree, I now realize that the explanation I put here is not good at all, I actually want to say that the io-worker already set refs = 2 (also possible that prep_link_out set 1, and io-worker adds the other 1, previously I miss this situation). One will be put at completion time, the other one will be put in io_wq_free_work(). So no need to set the refcount here again. I looked into io_req_set_refcount(), since it does nothing if refcount is already not zero, I should be ok to keep this one as it was. > >> +     * already explicitly set the submittion and completion ref. So no > > I'd say there is no notion of submission vs completion refs anymore. > >> +     * need to set refcount here if that is the case. >> +     */ >> +    if (!(req->flags & REQ_F_REFCOUNT)) > > Compare it with io_req_set_refcount(), that "if" is a a no-op > >> +        io_req_set_refcount(req); >>       ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask, >>                       io_async_wake); >> @@ -6704,8 +6710,11 @@ static void io_wq_submit_work(struct io_wq_work >> *work) >>           ret = -ECANCELED; >>       if (!ret) { >> +        bool need_poll = req->flags & REQ_F_ASYNC_HYBRID; >> + >>           do { >> -            ret = io_issue_sqe(req, 0); >> +issue_sqe: >> +            ret = io_issue_sqe(req, need_poll ? IO_URING_F_NONBLOCK : >> 0); > > It's buggy, you will get all kinds of kernel crashes and leaks. > Currently IO_URING_F_NONBLOCK has dual meaning: obvious nonblock but > also whether we hold uring_lock or not. You'd need to split the flag > into two, i.e. IO_URING_F_LOCKED I'll look into it. I was thinking about to do the first nowait try in the original context, but then I thought it doesn't make sense to bring up a worker just for poll infra arming since thread creating and scheduling has its overhead. >