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 DB91DEB64DD for ; Sun, 16 Jul 2023 20:30:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232131AbjGPUaT (ORCPT ); Sun, 16 Jul 2023 16:30:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51770 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232120AbjGPUaT (ORCPT ); Sun, 16 Jul 2023 16:30:19 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E7D4E46; Sun, 16 Jul 2023 13:30:15 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A12AC60EAE; Sun, 16 Jul 2023 20:30:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AF745C433C7; Sun, 16 Jul 2023 20:30:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689539414; bh=ExzEbA/RIzTxjKUcd5Ih5Si564HbUIS8oZ/FuVczb5g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UANksxT4i2gk58mCdpEjB/JIRdD+KqDeUfEMyEsliBgk+GGhzyYYrPRTuBannQ6VV +bqW/b8oWQ8nh2Mbs0ue0SJTtyX+z1Rl/i6ucvIU2woSmCL4FGmLNgQBIcbkl+X+4r vepNY1w8q8m0LkFIZDFiLWtx2ACnkIuOVVRgdOS0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Pavel Begunkov , io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, Andres Freund , Jens Axboe Subject: [PATCH 6.4 800/800] io_uring: Use io_schedule* in cqring wait Date: Sun, 16 Jul 2023 21:50:53 +0200 Message-ID: <20230716195007.731909670@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230716194949.099592437@linuxfoundation.org> References: <20230716194949.099592437@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org From: Andres Freund commit 8a796565cec3601071cbbd27d6304e202019d014 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- io_uring/io_uring.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2575,6 +2575,8 @@ int io_run_task_work_sig(struct io_ring_ 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))) @@ -2585,11 +2587,20 @@ static inline int io_cqring_wait_schedul 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; } /*