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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79F42C433FE for ; Wed, 11 May 2022 15:11:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243834AbiEKPLp (ORCPT ); Wed, 11 May 2022 11:11:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245619AbiEKPLb (ORCPT ); Wed, 11 May 2022 11:11:31 -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 DDB8F5C757 for ; Wed, 11 May 2022 08:11:28 -0700 (PDT) Received: by mail-wr1-x433.google.com with SMTP id v12so3410291wrv.10 for ; Wed, 11 May 2022 08:11:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Ynra/fwZ57AqLb2foGK1nUvHu8nGsV1n1grQhysZz74=; b=d+t8B6V9/rDivnEKZQmbIZAm2Ytm2FgRr6A4Tpk7jT7JgeKUz5A+OHiXd8QgdWlF5h iddCePbq7jl+rn4DTcfaIhagWdSTrl04nq95GQstz/7Jk0kXgjVUc5M+Js80ZcKMtndk vl3xxEB1HsaFDXunrClsmprmNfS/yA39/LM+L26Fwl9fhshz482gJUa/On2Y5OwbvcPn 8MO6ZsQc3/Cl/AMHCSFGlOksT29nfnhHmMd3gZT6WYrbdsp447512fJI3Q2LZu0+CAzt S+PaTmDRPVhP/OpnQqh3pr2+mWd5efkhnMhkhh858g0/uuvTGvb7dzj1JNEk7+/+l9/w SqMA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Ynra/fwZ57AqLb2foGK1nUvHu8nGsV1n1grQhysZz74=; b=I1Aoqka8x+xztICOgWcwc1WZf8WOfYt8kYC7xOXI/3ztQZBKglx/P1XQLGqPeBZqzW Kzg/MxWXpm5Ikk7HwEHOob9nM52aiXumjrs5rHKrDIbz+oz/KyWGSWdb44hUuEBSESuP fShOOmkwDEiAen7gZfP/rUSCGRt/ALeiYfWgOUsEsuB5+g/VPIPBu29RaWgp145Rk6kx Sco9UIRSYxCdHE/S7Tgks4damjYYja2J6URPjVV7JpjLRdyTLWVIynGz02Zp8n+EnB9f mWCP1/JySSeF1ioU20X7HRKP5b824sCdLbrlQslNkJGPENkadSW925Mg70j3S50eEfct HtaA== X-Gm-Message-State: AOAM530TfJXsoBcVLoSzQf398GxBgtFHwpVf8j2Q0tvUJt4uzAuHdUh/ GiTzL+YZTnXrLI31ahKJ0s89FTo+ranj2uOVE58= X-Google-Smtp-Source: ABdhPJzdJaTalOfhP3Dxx75HMAkGgf8LWk4vbC6GXAvBnbFmWvYnH7gCivtOXTff0T7v87NarBMWIhVsbAXo3x3142A= X-Received: by 2002:adf:fa42:0:b0:20a:e8d6:58b8 with SMTP id y2-20020adffa42000000b0020ae8d658b8mr23678372wrr.64.1652281887309; Wed, 11 May 2022 08:11:27 -0700 (PDT) MIME-Version: 1.0 References: <6fc53990-1814-a45d-7c05-a4385246406c@kernel.dk> <744d4b58-e7df-a5fb-dfba-77fe952fe1f8@kernel.dk> <71956172-5406-0636-060d-a7c123a2bfab@kernel.dk> In-Reply-To: From: Constantine Gavrilov Date: Wed, 11 May 2022 18:11:16 +0300 Message-ID: Subject: Re: Short sends returned in IORING To: Jens Axboe Cc: io-uring@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Wed, May 11, 2022 at 5:56 PM Constantine Gavrilov wrote: > > On Wed, May 4, 2022 at 6:55 PM Jens Axboe wrote: > > > > On 5/4/22 9:28 AM, Jens Axboe wrote: > > > On 5/4/22 9:21 AM, Constantine Gavrilov wrote: > > >> On Wed, May 4, 2022 at 4:54 PM Jens Axboe wrote: > > >>> > > >>> On 5/3/22 5:05 PM, Constantine Gavrilov wrote: > > >>>> Jens: > > >>>> > > >>>> This is related to the previous thread "Fix MSG_WAITALL for > > >>>> IORING_OP_RECV/RECVMSG". > > >>>> > > >>>> We have a similar issue with TCP socket sends. I see short sends > > >>>> regarding of the method (I tried write, writev, send, and sendmsg > > >>>> opcodes, while using MSG_WAITALL for send and sendmsg). It does not > > >>>> make a difference. > > >>>> > > >>>> Most of the time, sends are not short, and I never saw short sends > > >>>> with loopback and my app. But on real network media, I see short > > >>>> sends. > > >>>> > > >>>> This is a real problem, since because of this it is not possible to > > >>>> implement queue size of > 1 on a TCP socket, which limits the benefit > > >>>> of IORING. When we have a short send, the next send in queue will > > >>>> "corrupt" the stream. > > >>>> > > >>>> Can we have complete send before it completes, unless the socket is > > >>>> disconnected? > > >>> > > >>> I'm guessing that this happens because we get a task_work item queued > > >>> after we've processed some of the send, but not all. What kernel are you > > >>> using? > > >>> > > >>> This: > > >>> > > >>> https://git.kernel.dk/cgit/linux-block/commit/?h=for-5.19/io_uring&id=4c3c09439c08b03d9503df0ca4c7619c5842892e > > >>> > > >>> is queued up for 5.19, would be worth trying. > > >>> > > >>> -- > > >>> Jens Axboe > > >>> > > >> > > >> Jens: > > >> > > >> Thank you for your reply. > > >> > > >> The kernel is 5.17.4-200.fc35.x86_64. I have looked at the patch. With > > >> the solution in place, I am wondering whether it will be possible to > > >> use multiple uring send IOs on the same socket. I expect that Linux > > >> TCP will serialize multiple send operations on the same socket. I am > > >> not sure it happens with uring (meaning that socket is blocked for > > >> processing a new IO until the pending IO completes). Do I need > > >> IOSQE_IO_DRAIN / IOSQE_IO_LINK for this to work? Would not be optimal > > >> because of multiple different sockets in the same uring. While I > > >> already have a workaround in the form of a "software" queue for > > >> streaming data on TCP sockets, I would rather have kernel to do > > >> "native" queueing in sockets layer, and have exrtra CPU cycles > > >> available to the application. > > > > > > The patch above will mess with ordering potentially. If the cause is as > > > I suspect, task_work causing it to think it's signaled, then the better > > > approach may indeed be to just flush that work and retry without > > > re-queueing the current one. I can try a patch against 5.18 if you are > > > willing and able to test? > > > > You can try something like this, if you run my for-5.19/io_uring branch. > > I'd be curious to know if this solves the short send issue for you. > > > > > > diff --git a/fs/io_uring.c b/fs/io_uring.c > > index f6b6db216478..b835e80be1fa 100644 > > --- a/fs/io_uring.c > > +++ b/fs/io_uring.c > > @@ -5684,6 +5684,7 @@ static int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags) > > if (flags & MSG_WAITALL) > > min_ret = iov_iter_count(&kmsg->msg.msg_iter); > > > > +retry: > > ret = __sys_sendmsg_sock(sock, &kmsg->msg, flags); > > > > if (ret < min_ret) { > > @@ -5694,6 +5695,8 @@ static int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags) > > if (ret > 0 && io_net_retry(sock, flags)) { > > sr->done_io += ret; > > req->flags |= REQ_F_PARTIAL_IO; > > + if (io_run_task_work()) > > + goto retry; > > return io_setup_async_msg(req, kmsg); > > } > > req_set_fail(req); > > @@ -5744,6 +5747,7 @@ static int io_send(struct io_kiocb *req, unsigned int issue_flags) > > min_ret = iov_iter_count(&msg.msg_iter); > > > > msg.msg_flags = flags; > > +retry: > > ret = sock_sendmsg(sock, &msg); > > if (ret < min_ret) { > > if (ret == -EAGAIN && (issue_flags & IO_URING_F_NONBLOCK)) > > @@ -5755,6 +5759,8 @@ static int io_send(struct io_kiocb *req, unsigned int issue_flags) > > sr->buf += ret; > > sr->done_io += ret; > > req->flags |= REQ_F_PARTIAL_IO; > > + if (io_run_task_work()) > > + goto retry; > > return -EAGAIN; > > } > > req_set_fail(req); > > > > -- > > Jens Axboe > > > > Jens: > > I was able to test the first change on the top of Linus kernel git (5.18.0-rc6). > > I do not get short sends anymore, but I get corruption in sent > packets (corruption is detected by the receiver). It looks like short > sends handled by the patch intermix data from multiple send SQEs in > the stream, so ordering of multiple SQEs in URING becomes broken. > > To test it, I had two implementations of the send functions: > 1. Uses SEND opcode, asserts on short sends. No asserts but data corruption. > 2. Uses TCP send queue implementation (internally uses SEND and > SENDMSG opcodes in URING, only one pending send at a time, and tail of > the short sends is resent until all data is sent). This always works. > > I would like to test the second patch now. Is it on the top of the > first patch or by itself? Do I really need your tree for that? If yes, > can you send me the git pull info, please? > > -- > ---------------------------------------- > Constantine Gavrilov > Storage Architect > Master Inventor > Tel-Aviv IBM Storage Lab > 1 Azrieli Center, Tel-Aviv > ---------------------------------------- Jens: for git branch, is it under git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git? -- ---------------------------------------- Constantine Gavrilov Storage Architect Master Inventor Tel-Aviv IBM Storage Lab 1 Azrieli Center, Tel-Aviv ----------------------------------------