From patchwork Tue Jul 18 19:49:15 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jens Axboe X-Patchwork-Id: 13317658 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 33195C001E0 for ; Tue, 18 Jul 2023 19:49:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230322AbjGRTt2 (ORCPT ); Tue, 18 Jul 2023 15:49:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34838 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230232AbjGRTt1 (ORCPT ); Tue, 18 Jul 2023 15:49:27 -0400 Received: from mail-io1-xd36.google.com (mail-io1-xd36.google.com [IPv6:2607:f8b0:4864:20::d36]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 493349D for ; Tue, 18 Jul 2023 12:49:26 -0700 (PDT) Received: by mail-io1-xd36.google.com with SMTP id ca18e2360f4ac-760dff4b701so56223039f.0 for ; Tue, 18 Jul 2023 12:49:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20221208.gappssmtp.com; s=20221208; t=1689709765; x=1692301765; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=UGcQDjq/o6t2ObZfo2BKw3K7TL3Ez2D+npEQSf00g+U=; b=GYMNTAwW+OS0zoZ8XObYelbr9fY9Yib+JrDAtJHHTiuw70qayYxL/ylwZIh40Ucbq7 wDFwyQL0jEAe+MS1C+4QETQ1v++JeT+9s17I7YZ6S/Q+rboxZhtSRkJNvuKr4aPSLq7+ BvLVr5TulVNpo2Qp+Ylvcv4lcGRN9SuHA+WjUAVLIVtMz0PSeK9uPWrjDg2RkJC5xM9+ G/0BfnERVgn1kXLDH/Awb7m0ysfkRLp9faGnz44SHdJGk+r/E6kIdw4oEKUz6Dc71nli wRK2gTR1Ber0dZiMsKLR6rz1Fg8n2DaZehZ5P1DK8J2DfuiZLnH4g0AX+Q1tswMls1j5 UeZg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689709765; x=1692301765; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=UGcQDjq/o6t2ObZfo2BKw3K7TL3Ez2D+npEQSf00g+U=; b=IIzzq2p+/Uf6WUH7DCCkwzpeFNuTGMGcb9ixB09EODwlDLQKn+aTZw35/oo72Vezy+ wTsZgUAEkbd+o+bSORLV0jJGrxqeFdEp6nrnEQ4zsxhoNiJAOA/+bo17F3UP93/k/wt4 BuEhnUxzve8ByPYvtn+ve2uA6sjbMwXwb8b61b8smUTvLtPjk83VF1KZl782ZhLIa1t2 2dPBrf2cvJ1K4tXELg37MGjstF6j/z/DYtmNSpExMSD5vhOl/NizShZj/WaqJDQ5oJ0S flnOkdp5X6jmXxtWSkwMK7Bh/yfKE4smtjLoZU9EK3HjRY8/J6pt9GsVbxc3NNkjgNIx rtOA== X-Gm-Message-State: ABy/qLZiWHKH5eA3Ge/nRu8+5SxtVpXxRhY8L3CUJXakDJVeF2kvJB/i g0W2il70FnQcnVhWv4aoEffCjeelSfOkAYiKiPw= X-Google-Smtp-Source: APBJJlFIO3UOGhj4Q8FZLu786jEuJAwxrtkB8KVTPudnVyvyxdmg+TKa5o8O1UPQHVeMc+GdYyACUg== X-Received: by 2002:a92:1901:0:b0:345:e438:7381 with SMTP id 1-20020a921901000000b00345e4387381mr2341960ilz.2.1689709765277; Tue, 18 Jul 2023 12:49:25 -0700 (PDT) Received: from localhost.localdomain ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id v18-20020a92d252000000b00345e3a04f2dsm897463ilg.62.2023.07.18.12.49.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Jul 2023 12:49:24 -0700 (PDT) From: Jens Axboe To: io-uring@vger.kernel.org, linux-xfs@vger.kernel.org Cc: hch@lst.de, andres@anarazel.de, david@fromorbit.com, stable@vger.kernel.org, Pavel Begunkov , linux-kernel@vger.kernel.org, Jens Axboe Subject: [PATCH] io_uring: Use io_schedule* in cqring wait Date: Tue, 18 Jul 2023 13:49:15 -0600 Message-Id: <20230718194920.1472184-2-axboe@kernel.dk> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230718194920.1472184-1-axboe@kernel.dk> References: <20230718194920.1472184-1-axboe@kernel.dk> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org From: Andres Freund I observed poor performance of io_uring compared to synchronous IO. That turns out to be caused by deeper CPU idle states entered with io_uring, due to io_uring using plain schedule(), whereas synchronous IO uses io_schedule(). The losses due to this are substantial. On my cascade lake workstation, t/io_uring from the fio repository e.g. yields regressions between 20% and 40% with the following command: ./t/io_uring -r 5 -X0 -d 1 -s 1 -c 1 -p 0 -S$use_sync -R 0 /mnt/t2/fio/write.0.0 This is repeatable with different filesystems, using raw block devices and using different block devices. Use io_schedule_prepare() / io_schedule_finish() in io_cqring_wait_schedule() to address the difference. After that using io_uring is on par or surpassing synchronous IO (using registered files etc makes it reliably win, but arguably is a less fair comparison). There are other calls to schedule() in io_uring/, but none immediately jump out to be similarly situated, so I did not touch them. Similarly, it's possible that mutex_lock_io() should be used, but it's not clear if there are cases where that matters. Cc: stable@vger.kernel.org # 5.10+ Cc: Pavel Begunkov Cc: io-uring@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Andres Freund Link: https://lore.kernel.org/r/20230707162007.194068-1-andres@anarazel.de [axboe: minor style fixup] Signed-off-by: Jens Axboe --- io_uring/io_uring.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index e8096d502a7c..7505de2428e0 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2489,6 +2489,8 @@ int io_run_task_work_sig(struct io_ring_ctx *ctx) static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx, struct io_wait_queue *iowq) { + int token, ret; + if (unlikely(READ_ONCE(ctx->check_cq))) return 1; if (unlikely(!llist_empty(&ctx->work_llist))) @@ -2499,11 +2501,20 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx, return -EINTR; if (unlikely(io_should_wake(iowq))) return 0; + + /* + * Use io_schedule_prepare/finish, so cpufreq can take into account + * that the task is waiting for IO - turns out to be important for low + * QD IO. + */ + token = io_schedule_prepare(); + ret = 0; if (iowq->timeout == KTIME_MAX) schedule(); else if (!schedule_hrtimeout(&iowq->timeout, HRTIMER_MODE_ABS)) - return -ETIME; - return 0; + ret = -ETIME; + io_schedule_finish(token); + return ret; } /*