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,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 00F63C433ED for ; Wed, 28 Apr 2021 14:34:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AE3D961433 for ; Wed, 28 Apr 2021 14:34:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235893AbhD1Oe5 (ORCPT ); Wed, 28 Apr 2021 10:34:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235864AbhD1Oe5 (ORCPT ); Wed, 28 Apr 2021 10:34:57 -0400 Received: from mail-wr1-x435.google.com (mail-wr1-x435.google.com [IPv6:2a00:1450:4864:20::435]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C569C061573 for ; Wed, 28 Apr 2021 07:34:10 -0700 (PDT) Received: by mail-wr1-x435.google.com with SMTP id x7so63277385wrw.10 for ; Wed, 28 Apr 2021 07:34:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=XSphu27pumn6nx/Hg3UPMrOrVZL9ufQInaazixLiEJs=; b=mgeK2l2dLZ8mibw6k+/8/QkVHC/n5ISZ9DsE5HVnYCNP2CIudUdF4TsH8kMMkcI0wo pBHHza3qxw6knzGCKdXKOjj7/ucm9ndlQi6o2040Wxaa05N+K03cH7blRKVKhnKkvUGe H60D7lDwsFSBKpV0qJ7TwObZgNDx66vUgZSy/HH3iVyiRaTC6VICm70YlYTS1p+KMxtW ByXEZ7KBvMfvNbS5mgRG5B4Z3sqJJiU4/OEPPZXp+PYF3EdzqJuRssbtjWzt4zt7lWW2 eCBqrcw+N+uNgdilt6BZfB7ZiNqucQqNwDhVIJ2xRChXDhN9QlI8BEXkVbuzK++d6qqQ 1piQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=XSphu27pumn6nx/Hg3UPMrOrVZL9ufQInaazixLiEJs=; b=bFvyzNrLr1Y21ENpa+gPgnyKBsfdIcFkWdcRN/r98ZGtBGXRQcMJHufI50rtvZVAtV hgfOoIparAOm+OZhp1LOqj1TJo/F+3HCUcYRjifDOKRFUU5fkdlwaRJvfuevcx1fmgCA eMLaft4U5L6btOeeEf1EhuCA0SBFP70UXGQYbO73FHU63hjz17eADThdOgRL8mnQ7Oyz qj+uQywZ7CJpP5rAKyLsw5oZvX3Xsx6uD2dRO58fL9lq4XO5sEZw8DqrXkMZqEdGKOnP p+2SaM0QhW9Ey5aPtgLeIMzJQLU4NYv4o8ErFe+3jrMozbVMJN8OiMzQ2K6lJgt9v3Xh K5Hw== X-Gm-Message-State: AOAM531F8tpYaBOJXRPMZz3PhGL2MP1VA5MROktSPeuoNNOenV26icSb 9iHTUzjve7JjRp02F5b2kKGJALg4/V0= X-Google-Smtp-Source: ABdhPJyEWftJJmbayYZz5VhoXU/Qgf38WMeW7DftzDe5Sm9uFvZGDuvzDpm8mUN+Sum2cvcN08cHGw== X-Received: by 2002:a05:6000:1449:: with SMTP id v9mr10344684wrx.82.1619620448999; Wed, 28 Apr 2021 07:34:08 -0700 (PDT) Received: from [192.168.8.197] ([185.69.145.35]) by smtp.gmail.com with ESMTPSA id v13sm164911wrt.65.2021.04.28.07.34.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 Apr 2021 07:34:08 -0700 (PDT) Subject: Re: [PATCH RFC 5.13 2/2] io_uring: submit sqes in the original context when waking up sqthread To: Hao Xu , Jens Axboe Cc: io-uring@vger.kernel.org, Joseph Qi References: <1619616748-17149-1-git-send-email-haoxu@linux.alibaba.com> <1619616748-17149-3-git-send-email-haoxu@linux.alibaba.com> From: Pavel Begunkov Message-ID: <571b5633-3286-feba-af6b-e388f52fc89b@gmail.com> Date: Wed, 28 Apr 2021 15:34:04 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: <1619616748-17149-3-git-send-email-haoxu@linux.alibaba.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 4/28/21 2:32 PM, Hao Xu wrote: > sqes are submitted by sqthread when it is leveraged, which means there > is IO latency when waking up sqthread. To wipe it out, submit limited > number of sqes in the original task context. > Tests result below: Frankly, it can be a nest of corner cases if not now then in the future, leading to a high maintenance burden. Hence, if we consider the change, I'd rather want to limit the userspace exposure, so it can be removed if needed. A noticeable change of behaviour here, as Hao recently asked, is that the ring can be passed to a task from a completely another thread group, and so the feature would execute from that context, not from the original/sqpoll one. Not sure IORING_ENTER_SQ_DEPUTY knob is needed, but at least can be ignored if the previous point is addressed. > > 99th latency: > iops\idle 10us 60us 110us 160us 210us 260us 310us 360us 410us 460us 510us > with this patch: > 2k 13 13 12 13 13 12 12 11 11 10.304 11.84 > without this patch: > 2k 15 14 15 15 15 14 15 14 14 13 11.84 Not sure the second nine describes it well enough, please can you add more data? Mean latency, 50%, 90%, 99%, 99.9%, t-put. Btw, how happened that only some of the numbers have fractional part? Can't believe they all but 3 were close enough to integer values. > fio config: > ./run_fio.sh > fio \ > --ioengine=io_uring --sqthread_poll=1 --hipri=1 --thread=1 --bs=4k \ > --direct=1 --rw=randread --time_based=1 --runtime=300 \ > --group_reporting=1 --filename=/dev/nvme1n1 --sqthread_poll_cpu=30 \ > --randrepeat=0 --cpus_allowed=35 --iodepth=128 --rate_iops=${1} \ > --io_sq_thread_idle=${2} > > Signed-off-by: Hao Xu > --- > fs/io_uring.c | 29 +++++++++++++++++++++++------ > include/uapi/linux/io_uring.h | 1 + > 2 files changed, 24 insertions(+), 6 deletions(-) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index 1871fad48412..f0a01232671e 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -1252,7 +1252,12 @@ static void io_queue_async_work(struct io_kiocb *req) > { > struct io_ring_ctx *ctx = req->ctx; > struct io_kiocb *link = io_prep_linked_timeout(req); > - struct io_uring_task *tctx = req->task->io_uring; > + struct io_uring_task *tctx = NULL; > + > + if (ctx->sq_data && ctx->sq_data->thread) > + tctx = ctx->sq_data->thread->io_uring; without park it's racy, sq_data->thread may become NULL and removed, as well as its ->io_uring. > + else > + tctx = req->task->io_uring; > > BUG_ON(!tctx); > BUG_ON(!tctx->io_wq); [snip] -- Pavel Begunkov