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=-14.2 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,URIBL_BLOCKED, 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 BCDDEC2B9F4 for ; Tue, 22 Jun 2021 20:52:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9A85061351 for ; Tue, 22 Jun 2021 20:52:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229775AbhFVUzJ (ORCPT ); Tue, 22 Jun 2021 16:55:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49002 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229758AbhFVUzI (ORCPT ); Tue, 22 Jun 2021 16:55:08 -0400 Received: from mail-wr1-x42c.google.com (mail-wr1-x42c.google.com [IPv6:2a00:1450:4864:20::42c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7EE64C061574; Tue, 22 Jun 2021 13:52:52 -0700 (PDT) Received: by mail-wr1-x42c.google.com with SMTP id a11so124534wrt.13; Tue, 22 Jun 2021 13:52:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=yO+UtMV4S0iaGuCkmp1qmwqtSoq6ABWJClMRuQMocdY=; b=GtL2h2yDpdNEnZUCLwVb/CSlr9f4wkoFGiuRuZ4iu7qnSA5sl8Pomnn8OurR0hEnX6 o5MYWkg+mMFsGCTh7eYC7L0VEUIBYSo4vBKJe+Kp9Iyd50K08Yp8ALYO9+/YvfWGDRqZ c0/TIFwMqHNvGiFeDanOkV6DU23G+am3w7Dbx7bn/o50OX23Gto3k8KakUxJ7I9ocBbZ IZlvTGOMCSvMk28VLn9gQ7i2QC8nK/eYCl9uFeLGg8sY3iiYA8dKV1+KUvzmQxYQLJ+r a/gBARgtXda124LKHp5buQESCuaXhyCM7D627CrcuEI6mj/A3q8XdMm2mo8Dt5bItW2S jHrA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=yO+UtMV4S0iaGuCkmp1qmwqtSoq6ABWJClMRuQMocdY=; b=PygErogtTot1xVyoQsKM3QPfsFxJALzOP3vQobdyM4jgFl2qOLWmqseiPPF0km08yD jmEheCjQDNPRIeHTVTDqoP4PXZM28kxUtyPMnJ2PDg/NX5T0ebqW0sqb+QdQTAteluqA DjPnQsnaymeB4kX3JE86pvSKviK0OLUNaM0NTnzIQzTNCbD/iw46O4XndS7RnkTA38Vk KMCtJA2oN+TRSdboeo0GyJfwAI/HHJ7wGh/H/UrfoNGst3AcpznnEk4tsAv11Gota3ws natTq5dWIUy/EF/msnyf+J8PRc/1XKragnfSF5wM0ZZ0VH1MmQc4TYub1GlG50tpmiGS n1BQ== X-Gm-Message-State: AOAM53262FIyqFqgUPKBrCJwr8KWPsJWHRIyHFOtYOBxpeksP6DvJzYj 4Lx8p+3p97Ve9FQaGaAQ4N4Ms6QuIYuhADCN X-Google-Smtp-Source: ABdhPJwcNx+UGi+gwo8RIrt3hNZRWK+mj8rOCKoZmSSrrRkUTcAPP2UZXDwNtS1Nq0GOI5qBrmZ5FQ== X-Received: by 2002:a5d:528d:: with SMTP id c13mr7244976wrv.343.1624395170925; Tue, 22 Jun 2021 13:52:50 -0700 (PDT) Received: from [192.168.8.197] ([148.252.132.93]) by smtp.gmail.com with ESMTPSA id o203sm3803624wmo.36.2021.06.22.13.52.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Jun 2021 13:52:50 -0700 (PDT) Subject: Re: [PATCH v4] io_uring: reduce latency by reissueing the operation To: Olivier Langlois , Jens Axboe , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org References: <9e8441419bb1b8f3c3fcc607b2713efecdef2136.1624364038.git.olivier@trillion01.com> From: Pavel Begunkov Message-ID: Date: Tue, 22 Jun 2021 21:52:37 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <9e8441419bb1b8f3c3fcc607b2713efecdef2136.1624364038.git.olivier@trillion01.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 6/22/21 1:17 PM, Olivier Langlois wrote: > It is quite frequent that when an operation fails and returns EAGAIN, > the data becomes available between that failure and the call to > vfs_poll() done by io_arm_poll_handler(). Looks good Reviewed-by: Pavel Begunkov > Detecting the situation and reissuing the operation is much faster > than going ahead and push the operation to the io-wq. > > Performance improvement testing has been performed with: > Single thread, 1 TCP connection receiving a 5 Mbps stream, no sqpoll. > > 4 measurements have been taken: > 1. The time it takes to process a read request when data is already available > 2. The time it takes to process by calling twice io_issue_sqe() after vfs_poll() indicated that data was available > 3. The time it takes to execute io_queue_async_work() > 4. The time it takes to complete a read request asynchronously > > 2.25% of all the read operations did use the new path. > > ready data (baseline) > avg 3657.94182918628 > min 580 > max 20098 > stddev 1213.15975908162 > > reissue completion > average 7882.67567567568 > min 2316 > max 28811 > stddev 1982.79172973284 > > insert io-wq time > average 8983.82276995305 > min 3324 > max 87816 > stddev 2551.60056552038 > > async time completion > average 24670.4758861127 > min 10758 > max 102612 > stddev 3483.92416873804 > > Conclusion: > On average reissuing the sqe with the patch code is 1.1uSec faster and > in the worse case scenario 59uSec faster than placing the request on > io-wq > > On average completion time by reissuing the sqe with the patch code is > 16.79uSec faster and in the worse case scenario 73.8uSec faster than > async completion. > > Signed-off-by: Olivier Langlois > --- > fs/io_uring.c | 31 ++++++++++++++++++++++--------- > 1 file changed, 22 insertions(+), 9 deletions(-) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index fc8637f591a6..5efa67c2f974 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -5152,7 +5152,13 @@ static __poll_t __io_arm_poll_handler(struct io_kiocb *req, > return mask; > } > > -static bool io_arm_poll_handler(struct io_kiocb *req) > +enum { > + IO_APOLL_OK, > + IO_APOLL_ABORTED, > + IO_APOLL_READY > +}; > + > +static int io_arm_poll_handler(struct io_kiocb *req) > { > const struct io_op_def *def = &io_op_defs[req->opcode]; > struct io_ring_ctx *ctx = req->ctx; > @@ -5162,22 +5168,22 @@ static bool io_arm_poll_handler(struct io_kiocb *req) > int rw; > > if (!req->file || !file_can_poll(req->file)) > - return false; > + return IO_APOLL_ABORTED; > if (req->flags & REQ_F_POLLED) > - return false; > + return IO_APOLL_ABORTED; > if (def->pollin) > rw = READ; > else if (def->pollout) > rw = WRITE; > else > - return false; > + return IO_APOLL_ABORTED; > /* if we can't nonblock try, then no point in arming a poll handler */ > if (!io_file_supports_async(req, rw)) > - return false; > + return IO_APOLL_ABORTED; > > apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC); > if (unlikely(!apoll)) > - return false; > + return IO_APOLL_ABORTED; > apoll->double_poll = NULL; > > req->flags |= REQ_F_POLLED; > @@ -5203,12 +5209,14 @@ static bool io_arm_poll_handler(struct io_kiocb *req) > if (ret || ipt.error) { > io_poll_remove_double(req); > spin_unlock_irq(&ctx->completion_lock); > - return false; > + if (ret) > + return IO_APOLL_READY; > + return IO_APOLL_ABORTED; > } > spin_unlock_irq(&ctx->completion_lock); > trace_io_uring_poll_arm(ctx, req, req->opcode, req->user_data, > mask, apoll->poll.events); > - return true; > + return IO_APOLL_OK; > } > > static bool __io_poll_remove_one(struct io_kiocb *req, > @@ -6437,6 +6445,7 @@ static void __io_queue_sqe(struct io_kiocb *req) > struct io_kiocb *linked_timeout = io_prep_linked_timeout(req); > int ret; > > +issue_sqe: > ret = io_issue_sqe(req, IO_URING_F_NONBLOCK|IO_URING_F_COMPLETE_DEFER); > > /* > @@ -6456,12 +6465,16 @@ static void __io_queue_sqe(struct io_kiocb *req) > io_put_req(req); > } > } else if (ret == -EAGAIN && !(req->flags & REQ_F_NOWAIT)) { > - if (!io_arm_poll_handler(req)) { > + switch (io_arm_poll_handler(req)) { > + case IO_APOLL_READY: > + goto issue_sqe; > + case IO_APOLL_ABORTED: > /* > * Queued up for async execution, worker will release > * submit reference when the iocb is actually submitted. > */ > io_queue_async_work(req); > + break; > } > } else { > io_req_complete_failed(req, ret); > -- Pavel Begunkov