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 15E39C433B4 for ; Wed, 28 Apr 2021 14:37:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE8C661434 for ; Wed, 28 Apr 2021 14:37:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240157AbhD1Oie (ORCPT ); Wed, 28 Apr 2021 10:38:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35628 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233516AbhD1Oib (ORCPT ); Wed, 28 Apr 2021 10:38:31 -0400 Received: from mail-wm1-x330.google.com (mail-wm1-x330.google.com [IPv6:2a00:1450:4864:20::330]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4501AC061573 for ; Wed, 28 Apr 2021 07:37:45 -0700 (PDT) Received: by mail-wm1-x330.google.com with SMTP id f15-20020a05600c4e8fb029013f5599b8a9so7356385wmq.1 for ; Wed, 28 Apr 2021 07:37:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:from:to:cc:references:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=Bif/XwW/p7JgjM8unkChqyQOqK1cQtJBGndRSEGeunM=; b=Cix9gkGjZH+zyF4E1OOlM4h2nDMSlQU7KctkRlZBevDSnfeaBQuybDwECReZf4PhwF 94hgW6ikxYcWpnYhqsMg15VAOv/bHqHK10NLP81Q9f30GdOKM/DbOvaDcjajHbuvG07E smHMuJ45tJd8JN393MVrlOzmemdoX8Ho6IsiuiNIUkAw8R5Mf8TxiEPGV6l0QnxilrAg zBDx/Mugu3Mli78H3lP0KDfd9dxNgeBtAaZdn616Hr63pHF8/0nehEK2IhHzI1ei3BwR AK+Hcd5NL2Y+FdEjXULh7Yk9FUmvScvGJ+0b16Ykt1CV7vdEjbTFDPqe2OtYMhluAJGd 8dWg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=Bif/XwW/p7JgjM8unkChqyQOqK1cQtJBGndRSEGeunM=; b=eMknGKghYxfJ4KAuuRDaop7hoN/LvalW/qiayGkeAQylXXRn9Nz54oC7uj5U2aBRRh A2LNOKIbuFkpK1GoO54daD5jaWPqKw4RshP7UhmkS1Zgph6715DskMDkjro+FDid7qFA Xe7RXR4B7Anf5xOv3qASsSoYvNmQ97wfRfMEhIMYsuaNv/VD/JA2698wwlL/rlC0lyYu k6KUSNPgozW66ciAS8JNqcEscGH0hT2h/1fCGKWOiOJR9WOgju2ksh2dB83Z2z4X1Xid 9g4hdZfwxZu6F9sGFA6b6S8u0vvyG6ysnRZKM6WqgMulA6PEPYH4HStp+eDnJQJzIFeT TIxA== X-Gm-Message-State: AOAM532+uhCPR+5vARTP6Ugu2M5L9acWOpS7XzZBIdlKHL19bscDetXd bWylPkuyGUEwIoblsgYikic= X-Google-Smtp-Source: ABdhPJy7Btwd+RQgO6V7foPjTzPmfsCnR/RXlnil8vdlI1LUPBPZO4/fdCBg0otnvZlo19hsf756qw== X-Received: by 2002:a7b:c846:: with SMTP id c6mr4803860wml.75.1619620664036; Wed, 28 Apr 2021 07:37:44 -0700 (PDT) Received: from [192.168.8.197] ([185.69.145.35]) by smtp.gmail.com with ESMTPSA id v20sm4184529wmj.15.2021.04.28.07.37.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 Apr 2021 07:37:43 -0700 (PDT) Subject: Re: [PATCH RFC 5.13 2/2] io_uring: submit sqes in the original context when waking up sqthread From: Pavel Begunkov 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> <571b5633-3286-feba-af6b-e388f52fc89b@gmail.com> Message-ID: <6cc0020d-bfad-d723-6cc3-8bb2b8c4d313@gmail.com> Date: Wed, 28 Apr 2021 15:37:39 +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: <571b5633-3286-feba-af6b-e388f52fc89b@gmail.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 3:34 PM, Pavel Begunkov wrote: > 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. So maybe something like: if (same_thread_group()) { /* submit */ } > > Not sure IORING_ENTER_SQ_DEPUTY knob is needed, but at least can be > ignored if the previous point is addressed. I'd question whether it'd be better with the flag or without doing this feature by default. > >> >> 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