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=-5.2 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,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 A52A0C2BA83 for ; Fri, 14 Feb 2020 15:48:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6B4092086A for ; Fri, 14 Feb 2020 15:48:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="1xsYCij8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729472AbgBNPsA (ORCPT ); Fri, 14 Feb 2020 10:48:00 -0500 Received: from mail-io1-f67.google.com ([209.85.166.67]:41378 "EHLO mail-io1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729090AbgBNPr7 (ORCPT ); Fri, 14 Feb 2020 10:47:59 -0500 Received: by mail-io1-f67.google.com with SMTP id m25so10999740ioo.8 for ; Fri, 14 Feb 2020 07:47:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=9cm9nMe+tq4lmZTcYutNgobi54J7NwX7ziEbQU5p76Y=; b=1xsYCij8TWXrLs6rL6xUzjdj3XD/ejSu4AMs5RVjDGaYucjnopJSMn1iYVETHocfOM uwRhmxMmE5Il6jOQmzDWybDjaEWXMagNiiT9VDZEtGd72RwFZaR1NewuuPOZVYdHgIqn r0InRYNz8ys9irI5V2P0MVOteWd1xNqNo+dWngC2Ys4lnmK5CPjJsWPl9OTErhUS2QSf oQVecGIjckwfiU4XHTRB68WM+S9fzvK0BzAfhSN9pcLHUh+NJkc2N5Hw0X51m5wEj4Pb Hi1il0MF5+O1KeHJU3VSaxFbQnYl2JWwERx/9I9OPndfce35F38MyF5u3VWQClTkAXgw 3sNw== 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=9cm9nMe+tq4lmZTcYutNgobi54J7NwX7ziEbQU5p76Y=; b=jpuPjtmtsVZ5vZYKahp99xGTWND/0Ue3n9iC3zjleiwdDiYk2vIApfeC3+njDHSUHl I+dplbHoywIZkMM70cczSe9zarNQ3PYRf3gIoPv9lOkHEV+9VLoMYZGQ3FyWEc4V+OGi Yrj0Nvhr+zl926/MekJKqJm5QUK7wxC8B0w1S5TCWDP4v6wT4LpkPrrpA3ryO8PDeoew sPwzyAQRDQECocBgWATYvtwkkQwX58yv3/Z+7x4j7YIdfQk7/LOQK0hnm0XSytW68gro TtoTUlaekUqYgdJ8wWNYNNywps5/QIVMC6J6XAxMlyyqg+Iv5IKO3sc9sNm5URK9igZT bEnA== X-Gm-Message-State: APjAAAVdh7e5sxbD0OCcnyoflq/yTKujrcMhzABIeQCkIQVBb3ETHsgt W8PLKfLuloLt0/FL/6JTrlojQnMSkzo= X-Google-Smtp-Source: APXvYqy32gBfgM64NhDo4QJelVzLiDS9QFrmFHJOnwchkP/Ml5RHmYuK50WMNiQatQCSfPKPTw/bLw== X-Received: by 2002:a5d:9708:: with SMTP id h8mr2800933iol.141.1581695277515; Fri, 14 Feb 2020 07:47:57 -0800 (PST) Received: from [192.168.1.159] ([65.144.74.34]) by smtp.gmail.com with ESMTPSA id v18sm2088283ilm.85.2020.02.14.07.47.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 14 Feb 2020 07:47:57 -0800 (PST) Subject: Re: [ISSUE] The time cost of IOSQE_IO_LINK To: Peter Zijlstra Cc: =?UTF-8?B?Q2FydGVyIExpIOadjumAmua0sg==?= , Pavel Begunkov , io-uring References: <9FEF0D34-A012-4505-AA4E-FF97CC302A33@eoitek.com> <8a3ee653-77ed-105d-c1c3-87087451914e@kernel.dk> <9a8e4c8a-f8b2-900d-92b6-cc69b6adf324@gmail.com> <5f09d89a-0c6d-47c2-465c-993af0c7ae71@kernel.dk> <7E66D70C-BE4E-4236-A49B-9843F66EA322@eoitek.com> <671A3FE3-FA12-43D8-ADF0-D1DB463B053F@eoitek.com> <217eda7b-3742-a50b-7d6a-c1294a85c8e0@kernel.dk> <1b9a7390-7539-a8bc-d437-493253b13d77@kernel.dk> <20200214153218.GM14914@hirez.programming.kicks-ass.net> From: Jens Axboe Message-ID: <5995f84e-8a6c-e774-6bb5-5b9b87a9cd3c@kernel.dk> Date: Fri, 14 Feb 2020 08:47:56 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200214153218.GM14914@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 2/14/20 8:32 AM, Peter Zijlstra wrote: > On Thu, Feb 13, 2020 at 10:03:54PM -0700, Jens Axboe wrote: > >> CC'ing peterz for some cluebat knowledge. Peter, is there a nice way to >> currently do something like this? Only thing I'm currently aware of is >> the preempt in/out notifiers, but they don't quite provide what I need, >> since I need to pass some data (a request) as well. > > Whee, nothing quite like this around I think. Probably not ;-) >> The full detail on what I'm trying here is: >> >> io_uring can have linked requests. One obvious use case for that is to >> queue a POLLIN on a socket, and then link a read/recv to that. When the >> poll completes, we want to run the read/recv. io_uring hooks into the >> waitqueue wakeup handler to finish the poll request, and since we're >> deep in waitqueue wakeup code, it queues the linked read/recv for >> execution via an async thread. This is not optimal, obviously, as it >> relies on a switch to a new thread to perform this read. This hack >> queues a backlog to the task itself, and runs it when it's scheduled in. >> Probably want to do the same for sched out as well, currently I just >> hack that in the io_uring wait part... > > I'll definitely need to think more about this, but a few comments on the > below. > >> +static void __io_uring_task_handler(struct list_head *list) >> +{ >> + struct io_kiocb *req; >> + >> + while (!list_empty(list)) { >> + req = list_first_entry(list, struct io_kiocb, list); >> + list_del(&req->list); >> + >> + __io_queue_sqe(req, NULL); >> + } >> +} >> + >> +void io_uring_task_handler(struct task_struct *tsk) >> +{ >> + LIST_HEAD(list); >> + >> + raw_spin_lock_irq(&tsk->uring_lock); >> + if (!list_empty(&tsk->uring_work)) >> + list_splice_init(&tsk->uring_work, &list); >> + raw_spin_unlock_irq(&tsk->uring_lock); >> + >> + __io_uring_task_handler(&list); >> +} > >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >> index fc1dfc007604..b60f081cac17 100644 >> --- a/kernel/sched/core.c >> +++ b/kernel/sched/core.c >> @@ -2717,6 +2717,11 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p) >> INIT_HLIST_HEAD(&p->preempt_notifiers); >> #endif >> >> +#ifdef CONFIG_IO_URING >> + INIT_LIST_HEAD(&p->uring_work); >> + raw_spin_lock_init(&p->uring_lock); >> +#endif >> + >> #ifdef CONFIG_COMPACTION >> p->capture_control = NULL; >> #endif >> @@ -3069,6 +3074,20 @@ fire_sched_out_preempt_notifiers(struct task_struct *curr, >> >> #endif /* CONFIG_PREEMPT_NOTIFIERS */ >> >> +#ifdef CONFIG_IO_URING >> +extern void io_uring_task_handler(struct task_struct *tsk); >> + >> +static inline void io_uring_handler(struct task_struct *tsk) >> +{ >> + if (!list_empty(&tsk->uring_work)) >> + io_uring_task_handler(tsk); >> +} >> +#else /* !CONFIG_IO_URING */ >> +static inline void io_uring_handler(struct task_struct *tsk) >> +{ >> +} >> +#endif >> + >> static inline void prepare_task(struct task_struct *next) >> { >> #ifdef CONFIG_SMP >> @@ -3322,6 +3341,8 @@ asmlinkage __visible void schedule_tail(struct task_struct *prev) >> balance_callback(rq); >> preempt_enable(); >> >> + io_uring_handler(current); >> + >> if (current->set_child_tid) >> put_user(task_pid_vnr(current), current->set_child_tid); >> > > I suspect you meant to put that in finish_task_switch() which is the > tail end of every schedule(), schedule_tail() is the tail end of > clone(). > > Or maybe you meant to put it in (and rename) sched_update_worker() which > is after every schedule() but in a preemptible context -- much saner > since you don't want to go add an unbounded amount of work in a > non-preemptible context. > > At which point you already have your callback: io_wq_worker_running(), > or is this for any random task? Let me try and clarify - this isn't for the worker tasks, this is for any task that is using io_uring. In fact, it's particularly not for the worker threads, just the task itself. I basically want the handler to be called when: 1) The task is scheduled in. The poll will complete and stuff some items on that task list, and I want to task to process them as it wakes up. 2) The task is going to sleep, don't want to leave entries around while the task is sleeping. 3) I need it to be called from "normal" context, with ints enabled, preempt enabled, etc. sched_update_worker() (with a rename) looks ideal for #1, and the context is sane for me. Just need a good spot to put the hook call for schedule out. I think this: if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER)) { preempt_disable(); if (tsk->flags & PF_WQ_WORKER) wq_worker_sleeping(tsk); else io_wq_worker_sleeping(tsk); preempt_enable_no_resched(); } just needs to go into another helper, and then I can call it there outside of the preempt. I'm sure there are daemons lurking here, but I'll test and see how it goes... -- Jens Axboe