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 99E4AC433EF for ; Mon, 20 Jun 2022 16:19:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232831AbiFTQTU (ORCPT ); Mon, 20 Jun 2022 12:19:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43388 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241698AbiFTQTS (ORCPT ); Mon, 20 Jun 2022 12:19:18 -0400 Received: from mx0a-00082601.pphosted.com (mx0b-00082601.pphosted.com [67.231.153.30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CCC191A071 for ; Mon, 20 Jun 2022 09:19:13 -0700 (PDT) Received: from pps.filterd (m0001303.ppops.net [127.0.0.1]) by m0001303.ppops.net (8.17.1.5/8.17.1.5) with ESMTP id 25KFIPaK011083 for ; Mon, 20 Jun 2022 09:19:13 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=zYGS/n8k3uvuGZObQMwbKXywpH8/6iQ9ZHJq1Rfri/0=; b=qhteGOEFrLuPIuJZ5dMw8xQpIYzrFiFqEt1zUfqFx8uKbxpgSGK2W2Zv6loQ7sIcGR8k 0XSLQcBQ9htZNWDFjjE49BwZPV8O6gCLQ4n3u7H4xWdqv+peFsLiRlE3kOYyUzaOSqhm qP/gql4vNRCKuEZWG3LN0WWgUVMwLPH91BM= Received: from mail.thefacebook.com ([163.114.132.120]) by m0001303.ppops.net (PPS) with ESMTPS id 3gsacvt3em-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 20 Jun 2022 09:19:12 -0700 Received: from twshared25107.07.ash9.facebook.com (2620:10d:c085:108::8) by mail.thefacebook.com (2620:10d:c085:21d::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.28; Mon, 20 Jun 2022 09:19:10 -0700 Received: by devbig038.lla2.facebook.com (Postfix, from userid 572232) id 876961EB943E; Mon, 20 Jun 2022 09:19:05 -0700 (PDT) From: Dylan Yudaken To: , , CC: , Dylan Yudaken Subject: [PATCH RFC for-next 3/8] io_uring: lockless task list Date: Mon, 20 Jun 2022 09:18:56 -0700 Message-ID: <20220620161901.1181971-4-dylany@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220620161901.1181971-1-dylany@fb.com> References: <20220620161901.1181971-1-dylany@fb.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-ORIG-GUID: iajQQCX5tgVzJ7qFOWrmM1JAHKmhbAZh X-Proofpoint-GUID: iajQQCX5tgVzJ7qFOWrmM1JAHKmhbAZh X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.64.514 definitions=2022-06-20_05,2022-06-17_01,2022-02-23_01 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org With networking use cases we see contention on the spinlock used to protect the task_list when multiple threads try and add completions at on= ce. Instead we can use a lockless list, and assume that the first caller to add to the list is responsible for kicking off task work. Signed-off-by: Dylan Yudaken --- include/linux/io_uring_types.h | 2 +- io_uring/io_uring.c | 38 ++++++++-------------------------- io_uring/tctx.c | 3 +-- io_uring/tctx.h | 6 +++--- 4 files changed, 14 insertions(+), 35 deletions(-) diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_type= s.h index 5987f8acca38..918165a20053 100644 --- a/include/linux/io_uring_types.h +++ b/include/linux/io_uring_types.h @@ -428,7 +428,7 @@ typedef void (*io_req_tw_func_t)(struct io_kiocb *req= , bool *locked); =20 struct io_task_work { union { - struct io_wq_work_node node; + struct llist_node node; struct llist_node fallback_node; }; io_req_tw_func_t func; diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index e1523b62103b..985b46dfebb6 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -986,11 +986,12 @@ static void ctx_flush_and_put(struct io_ring_ctx *c= tx, bool *locked) percpu_ref_put(&ctx->refs); } =20 -static void handle_tw_list(struct io_wq_work_node *node, + +static void handle_tw_list(struct llist_node *node, struct io_ring_ctx **ctx, bool *locked) { do { - struct io_wq_work_node *next =3D node->next; + struct llist_node *next =3D node->next; struct io_kiocb *req =3D container_of(node, struct io_kiocb, io_task_work.node); =20 @@ -1014,23 +1015,11 @@ void tctx_task_work(struct callback_head *cb) struct io_ring_ctx *ctx =3D NULL; struct io_uring_task *tctx =3D container_of(cb, struct io_uring_task, task_work); + struct llist_node *node =3D llist_del_all(&tctx->task_list); =20 - while (1) { - struct io_wq_work_node *node; - - spin_lock_irq(&tctx->task_lock); - node =3D tctx->task_list.first; - INIT_WQ_LIST(&tctx->task_list); - if (!node) - tctx->task_running =3D false; - spin_unlock_irq(&tctx->task_lock); - if (!node) - break; + if (node) { handle_tw_list(node, &ctx, &uring_locked); cond_resched(); - - if (data_race(!tctx->task_list.first) && uring_locked) - io_submit_flush_completions(ctx); } =20 ctx_flush_and_put(ctx, &uring_locked); @@ -1044,16 +1033,10 @@ void io_req_task_work_add(struct io_kiocb *req) { struct io_uring_task *tctx =3D req->task->io_uring; struct io_ring_ctx *ctx =3D req->ctx; - struct io_wq_work_node *node; - unsigned long flags; + struct llist_node *node; bool running; =20 - spin_lock_irqsave(&tctx->task_lock, flags); - wq_list_add_tail(&req->io_task_work.node, &tctx->task_list); - running =3D tctx->task_running; - if (!running) - tctx->task_running =3D true; - spin_unlock_irqrestore(&tctx->task_lock, flags); + running =3D !llist_add(&req->io_task_work.node, &tctx->task_list); =20 /* task_work already pending, we're done */ if (running) @@ -1065,11 +1048,8 @@ void io_req_task_work_add(struct io_kiocb *req) if (likely(!task_work_add(req->task, &tctx->task_work, ctx->notify_meth= od))) return; =20 - spin_lock_irqsave(&tctx->task_lock, flags); - tctx->task_running =3D false; - node =3D tctx->task_list.first; - INIT_WQ_LIST(&tctx->task_list); - spin_unlock_irqrestore(&tctx->task_lock, flags); + + node =3D llist_del_all(&tctx->task_list); =20 while (node) { req =3D container_of(node, struct io_kiocb, io_task_work.node); diff --git a/io_uring/tctx.c b/io_uring/tctx.c index 7a68ba9beec3..7f97d97fef0a 100644 --- a/io_uring/tctx.c +++ b/io_uring/tctx.c @@ -86,8 +86,7 @@ __cold int io_uring_alloc_task_context(struct task_stru= ct *task, atomic_set(&tctx->in_idle, 0); atomic_set(&tctx->inflight_tracked, 0); task->io_uring =3D tctx; - spin_lock_init(&tctx->task_lock); - INIT_WQ_LIST(&tctx->task_list); + init_llist_head(&tctx->task_list); init_task_work(&tctx->task_work, tctx_task_work); return 0; } diff --git a/io_uring/tctx.h b/io_uring/tctx.h index c8566ea5dca4..8a33ff6e5d91 100644 --- a/io_uring/tctx.h +++ b/io_uring/tctx.h @@ -1,5 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 =20 +#include + /* * Arbitrary limit, can be raised if need be */ @@ -19,9 +21,7 @@ struct io_uring_task { struct percpu_counter inflight; =20 struct { /* task_work */ - spinlock_t task_lock; - bool task_running; - struct io_wq_work_list task_list; + struct llist_head task_list; struct callback_head task_work; } ____cacheline_aligned_in_smp; }; --=20 2.30.2