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 37930C433FE for ; Thu, 20 Oct 2022 14:52:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230274AbiJTOwL (ORCPT ); Thu, 20 Oct 2022 10:52:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33970 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230261AbiJTOwH (ORCPT ); Thu, 20 Oct 2022 10:52:07 -0400 Received: from hr2.samba.org (hr2.samba.org [IPv6:2a01:4f8:192:486::2:0]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E97F12A9F; Thu, 20 Oct 2022 07:52:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=samba.org; s=42; h=From:Cc:To:Date:Message-ID; bh=TIWtRz+9TftHiP5YNKoMEajC+fw9pADpE4a9PQRMj20=; b=2mTVvwe0Dq+A/LFaLlTa0R0tCD divDO81T0MAUebLwqijSydP8S8OyUZFL1+U3DBsIpxvbzHkDOoUnpS6FjfE0kJits20VrgMnTZxtc 7kdNeUSPqrTLBsVvorbE/9oP5LAG4wE9swUStE4luDaFFJxM+gxnm/bz4NEz4jg1qLvQiEK+qqYVP SWvjTQJ7AuAfJ3QY3sOvGQWlj06WadhFkBMThxS0g/IENDhhu/k2HNw1YikphQqoR+2q7Kue0dXq4 nYgGq8sIdSY0d1iUqGjzHpav4ZtM0oyzkz8qbt9covfSfI4H7RZR4wpaRtd51HC1KE5Q/VjKO8CwE Qdl7vm5q2O7YkhSNem6Y7UpikhjKJH3ad1/xHD1RU8NN0irodjN02lAAo3kXG0tjo9dLN9Q3RZ97U bMdWl59flgX8Cse8Fbqphu0tuMuxprTJCsEavLj5Iai24s4kdYf4D/qo5bJL7KPzlYNBxUN9dg6Rk 2Xp/hzsiIrY4cMYX2fq1VHPi; Received: from [127.0.0.2] (localhost [127.0.0.1]) by hr2.samba.org with esmtpsa (TLS1.3:ECDHE_SECP256R1__ECDSA_SECP256R1_SHA256__CHACHA20_POLY1305:256) (Exim) id 1olWtu-0051Pl-CE; Thu, 20 Oct 2022 14:52:03 +0000 Message-ID: Date: Thu, 20 Oct 2022 16:51:47 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Content-Language: en-US, de-DE To: Pavel Begunkov , io-uring , Jens Axboe Cc: Jakub Kicinski , netdev , Dylan Yudaken References: <4385ba84-55dd-6b08-0ca7-6b4a43f9d9a2@samba.org> <6f0a9137-2d2b-7294-f59f-0fcf9cdfc72d@gmail.com> <4bbf6bc1-ee4b-8758-7860-a06f57f35d14@samba.org> From: Stefan Metzmacher Subject: Re: IORING_SEND_NOTIF_REPORT_USAGE (was Re: IORING_CQE_F_COPIED) In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi Pavel, >> So far I came up with a IORING_SEND_NOTIF_REPORT_USAGE opt-in flag >> and the reporting is done in cqe.res with IORING_NOTIF_USAGE_ZC_USED (0x00000001) >> and/or IORING_NOTIF_USAGE_ZC_COPIED (0x8000000). So the caller is also >> able to notice that some parts were able to use zero copy, while other >> fragments were copied. > > Are we really interested in multihoming and probably some very edge cases? > I'd argue we're not and it should be a single bool hint indicating whether > zc is viable or not. It can do more complex calculations _if_ needed, e.g. > looking inside skb's and figure out how many bytes were copied but as for me > it should better be turned into a single bool in the end. Could also be the > number of bytes copied, but I don't think we can't have the accuracy for > that (e.g. what we're going to return if some protocol duplicates an skb > and sends to 2 different devices or is processing it in a pipeline?) > > So the question is what is the use case for having 2 flags? It's mostly for debugging. > btw, now we've got another example why the report flag is a good idea, I don't understand that line... > we can't use cqe.res unconditionally because we want to have a "one CQE > per request" mode, but it's fine if we make it and the report flag > mutually exclusive. You mean we can add an optimized case where SEND[MSG]_ZC would not generate F_MORE and skips F_NOTIF, because we copied or the transmission path was really fast? Then I'd move to IORING_CQE_F_COPIED again... >> I haven't tested it yet, but I want to post it early... >> >> What do you think? > > Keeping in mind potential backporting let's make it as simple and > short as possible first and then do optimisations on top. ok. >> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h >> index ab7458033ee3..751fc4eff8d1 100644 >> --- a/include/uapi/linux/io_uring.h >> +++ b/include/uapi/linux/io_uring.h >> @@ -296,10 +296,28 @@ enum io_uring_op { >>    * >>    * IORING_RECVSEND_FIXED_BUF    Use registered buffers, the index is stored in >>    *                the buf_index field. >> + * >> + * IORING_SEND_NOTIF_REPORT_USAGE >> + *                If SEND[MSG]_ZC should report >> + *                the zerocopy usage in cqe.res >> + *                for the IORING_CQE_F_NOTIF cqe. >> + *                IORING_NOTIF_USAGE_ZC_USED if zero copy was used >> + *                (at least partially). >> + *                IORING_NOTIF_USAGE_ZC_COPIED if data was copied >> + *                (at least partially). >>    */ >>   #define IORING_RECVSEND_POLL_FIRST    (1U << 0) >>   #define IORING_RECV_MULTISHOT        (1U << 1) >>   #define IORING_RECVSEND_FIXED_BUF    (1U << 2) >> +#define IORING_SEND_NOTIF_REPORT_USAGE    (1U << 3) >> + >> +/* >> + * cqe.res for IORING_CQE_F_NOTIF if >> + * IORING_SEND_NOTIF_REPORT_USAGE was requested >> + */ >> +#define IORING_NOTIF_USAGE_ZC_USED    (1U << 0) >> +#define IORING_NOTIF_USAGE_ZC_COPIED    (1U << 31) >> + >> >>   /* >>    * accept flags stored in sqe->ioprio >> diff --git a/io_uring/net.c b/io_uring/net.c >> index 735eec545115..a79d7d349e19 100644 >> --- a/io_uring/net.c >> +++ b/io_uring/net.c >> @@ -946,9 +946,11 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) >> >>       zc->flags = READ_ONCE(sqe->ioprio); >>       if (zc->flags & ~(IORING_RECVSEND_POLL_FIRST | >> -              IORING_RECVSEND_FIXED_BUF)) >> +              IORING_RECVSEND_FIXED_BUF | >> +              IORING_SEND_NOTIF_REPORT_USAGE)) >>           return -EINVAL; >> -    notif = zc->notif = io_alloc_notif(ctx); >> +    notif = zc->notif = io_alloc_notif(ctx, >> +                       zc->flags & IORING_SEND_NOTIF_REPORT_USAGE); >>       if (!notif) >>           return -ENOMEM; >>       notif->cqe.user_data = req->cqe.user_data; >> diff --git a/io_uring/notif.c b/io_uring/notif.c >> index e37c6569d82e..3844e3c8ad7e 100644 >> --- a/io_uring/notif.c >> +++ b/io_uring/notif.c >> @@ -3,13 +3,14 @@ >>   #include >>   #include >>   #include >> +#include > > Is it needed? No >>   #include >> >>   #include "io_uring.h" >>   #include "notif.h" >>   #include "rsrc.h" >> >> -static void __io_notif_complete_tw(struct io_kiocb *notif, bool *locked) >> +static inline void __io_notif_complete_tw(struct io_kiocb *notif, bool *locked) > > Let's remove this hunk with inlining and do it later > >>   { >>       struct io_notif_data *nd = io_notif_to_data(notif); >>       struct io_ring_ctx *ctx = notif->ctx; >> @@ -21,20 +22,46 @@ static void __io_notif_complete_tw(struct io_kiocb *notif, bool *locked) >>       io_req_task_complete(notif, locked); >>   } >> >> -static void io_uring_tx_zerocopy_callback(struct sk_buff *skb, >> -                      struct ubuf_info *uarg, >> -                      bool success) >> +static inline void io_uring_tx_zerocopy_callback(struct sk_buff *skb, >> +                         struct ubuf_info *uarg, >> +                         bool success) > > This one as well. > > >>   { >>       struct io_notif_data *nd = container_of(uarg, struct io_notif_data, uarg); >>       struct io_kiocb *notif = cmd_to_io_kiocb(nd); >> >>       if (refcount_dec_and_test(&uarg->refcnt)) { >> -        notif->io_task_work.func = __io_notif_complete_tw; >>           io_req_task_work_add(notif); >>       } >>   } >> >> -struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx) >> +static void __io_notif_complete_tw_report_usage(struct io_kiocb *notif, bool *locked) > > Just shove all that into __io_notif_complete_tw(). Ok, and then optimze later? Otherwise we could have IORING_CQE_F_COPIED by default without opt-in flag... >> +static void io_uring_tx_zerocopy_callback_report_usage(struct sk_buff *skb, >> +                            struct ubuf_info *uarg, >> +                            bool success) >> +{ >> +    struct io_notif_data *nd = container_of(uarg, struct io_notif_data, uarg); >> + >> +    if (success && !nd->zc_used && skb) >> +        nd->zc_used = true; >> +    else if (unlikely(!success && !nd->zc_copied)) >> +        nd->zc_copied = true; > > It's fine but racy, so let's WRITE_ONCE() to indicate it. I don't see how this could be a problem, but I can add it. >> diff --git a/io_uring/notif.h b/io_uring/notif.h >> index 5b4d710c8ca5..5ac7a2745e52 100644 >> --- a/io_uring/notif.h >> +++ b/io_uring/notif.h >> @@ -13,10 +13,12 @@ struct io_notif_data { >>       struct file        *file; >>       struct ubuf_info    uarg; >>       unsigned long        account_pages; >> +    bool            zc_used; >> +    bool            zc_copied; > > IIRC io_notif_data is fully packed in 6.1, so placing zc_{used,copied} > there might complicate backporting (if any). We can place them in io_kiocb > directly and move in 6.2. Alternatively account_pages doesn't have to be > long. As far as I can see kernel-dk-block/io_uring-6.1 alread has your shrink patches included...