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 E9E84C43334 for ; Mon, 20 Jun 2022 16:19:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240977AbiFTQT1 (ORCPT ); Mon, 20 Jun 2022 12:19:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43528 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236809AbiFTQT0 (ORCPT ); Mon, 20 Jun 2022 12:19:26 -0400 Received: from mx0a-00082601.pphosted.com (mx0a-00082601.pphosted.com [67.231.145.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C36916559 for ; Mon, 20 Jun 2022 09:19:25 -0700 (PDT) Received: from pps.filterd (m0109334.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 25KFYQNU027232 for ; Mon, 20 Jun 2022 09:19:25 -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=9CDkBmWADP2uAPuqCsYz0U9kZWynYEQ7Z/MI31M+C1U=; b=Y05WSgxAi1e+d8zktLQhsiaUcEn128zjUjNROabbWXsQiArjci4GxHYr1/LgIoDKJJif ypsox7zPO5Gxj/uW6VoaHX4KRZ/+P7aMNrlOWVRr1QIcx8SypVRrms9aoTQ/fGM/Lquq kLAQAMLMxaEVK/ovYyYM5ffOqLZFfGT7hsg= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3gtunfr9s3-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 20 Jun 2022 09:19:25 -0700 Received: from twshared22934.08.ash9.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::f) 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 09:19:24 -0700 Received: by devbig038.lla2.facebook.com (Postfix, from userid 572232) id 7A3E31EB943A; Mon, 20 Jun 2022 09:19:05 -0700 (PDT) From: Dylan Yudaken To: , , CC: , Dylan Yudaken Subject: [PATCH RFC for-next 1/8] io_uring: remove priority tw list optimisation Date: Mon, 20 Jun 2022 09:18:54 -0700 Message-ID: <20220620161901.1181971-2-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-GUID: 91KatCrxPhgsKeqv8S5VqGOvHG26vSz3 X-Proofpoint-ORIG-GUID: 91KatCrxPhgsKeqv8S5VqGOvHG26vSz3 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 This optimisation has some built in assumptions that make it easy to introduce bugs. It also does not have clear wins that make it worth keepi= ng. Signed-off-by: Dylan Yudaken --- io_uring/io_uring.c | 77 +++++++-------------------------------------- io_uring/io_uring.h | 1 - io_uring/rw.c | 2 +- io_uring/tctx.c | 1 - io_uring/tctx.h | 1 - 5 files changed, 12 insertions(+), 70 deletions(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index afda42246d12..cc524d33748d 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -986,44 +986,6 @@ static void ctx_flush_and_put(struct io_ring_ctx *ct= x, bool *locked) percpu_ref_put(&ctx->refs); } =20 -static void handle_prev_tw_list(struct io_wq_work_node *node, - struct io_ring_ctx **ctx, bool *uring_locked) -{ - if (*ctx && !*uring_locked) - spin_lock(&(*ctx)->completion_lock); - - do { - struct io_wq_work_node *next =3D node->next; - struct io_kiocb *req =3D container_of(node, struct io_kiocb, - io_task_work.node); - - prefetch(container_of(next, struct io_kiocb, io_task_work.node)); - - if (req->ctx !=3D *ctx) { - if (unlikely(!*uring_locked && *ctx)) - io_cq_unlock_post(*ctx); - - ctx_flush_and_put(*ctx, uring_locked); - *ctx =3D req->ctx; - /* if not contended, grab and improve batching */ - *uring_locked =3D mutex_trylock(&(*ctx)->uring_lock); - percpu_ref_get(&(*ctx)->refs); - if (unlikely(!*uring_locked)) - io_cq_lock(*ctx); - } - if (likely(*uring_locked)) { - req->io_task_work.func(req, uring_locked); - } else { - req->cqe.flags =3D io_put_kbuf_comp(req); - __io_req_complete_post(req); - } - node =3D next; - } while (node); - - if (unlikely(!*uring_locked)) - io_cq_unlock_post(*ctx); -} - static void handle_tw_list(struct io_wq_work_node *node, struct io_ring_ctx **ctx, bool *locked) { @@ -1054,27 +1016,20 @@ void tctx_task_work(struct callback_head *cb) task_work); =20 while (1) { - struct io_wq_work_node *node1, *node2; + struct io_wq_work_node *node; =20 spin_lock_irq(&tctx->task_lock); - node1 =3D tctx->prio_task_list.first; - node2 =3D tctx->task_list.first; + node =3D tctx->task_list.first; INIT_WQ_LIST(&tctx->task_list); - INIT_WQ_LIST(&tctx->prio_task_list); - if (!node2 && !node1) + if (!node) tctx->task_running =3D false; spin_unlock_irq(&tctx->task_lock); - if (!node2 && !node1) + if (!node) break; - - if (node1) - handle_prev_tw_list(node1, &ctx, &uring_locked); - if (node2) - handle_tw_list(node2, &ctx, &uring_locked); + handle_tw_list(node, &ctx, &uring_locked); cond_resched(); =20 - if (data_race(!tctx->task_list.first) && - data_race(!tctx->prio_task_list.first) && uring_locked) + if (data_race(!tctx->task_list.first) && uring_locked) io_submit_flush_completions(ctx); } =20 @@ -1086,8 +1041,7 @@ void tctx_task_work(struct callback_head *cb) } =20 static void __io_req_task_work_add(struct io_kiocb *req, - struct io_uring_task *tctx, - struct io_wq_work_list *list) + struct io_uring_task *tctx) { struct io_ring_ctx *ctx =3D req->ctx; struct io_wq_work_node *node; @@ -1095,7 +1049,7 @@ static void __io_req_task_work_add(struct io_kiocb = *req, bool running; =20 spin_lock_irqsave(&tctx->task_lock, flags); - wq_list_add_tail(&req->io_task_work.node, list); + wq_list_add_tail(&req->io_task_work.node, &tctx->task_list); running =3D tctx->task_running; if (!running) tctx->task_running =3D true; @@ -1113,7 +1067,8 @@ static void __io_req_task_work_add(struct io_kiocb = *req, =20 spin_lock_irqsave(&tctx->task_lock, flags); tctx->task_running =3D false; - node =3D wq_list_merge(&tctx->prio_task_list, &tctx->task_list); + node =3D tctx->task_list.first; + INIT_WQ_LIST(&tctx->task_list); spin_unlock_irqrestore(&tctx->task_lock, flags); =20 while (node) { @@ -1129,17 +1084,7 @@ void io_req_task_work_add(struct io_kiocb *req) { struct io_uring_task *tctx =3D req->task->io_uring; =20 - __io_req_task_work_add(req, tctx, &tctx->task_list); -} - -void io_req_task_prio_work_add(struct io_kiocb *req) -{ - struct io_uring_task *tctx =3D req->task->io_uring; - - if (req->ctx->flags & IORING_SETUP_SQPOLL) - __io_req_task_work_add(req, tctx, &tctx->prio_task_list); - else - __io_req_task_work_add(req, tctx, &tctx->task_list); + __io_req_task_work_add(req, tctx); } =20 static void io_req_tw_post(struct io_kiocb *req, bool *locked) diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h index 7a00bbe85d35..864e552c76a5 100644 --- a/io_uring/io_uring.h +++ b/io_uring/io_uring.h @@ -35,7 +35,6 @@ struct file *io_file_get_fixed(struct io_kiocb *req, in= t fd, bool io_is_uring_fops(struct file *file); bool io_alloc_async_data(struct io_kiocb *req); void io_req_task_work_add(struct io_kiocb *req); -void io_req_task_prio_work_add(struct io_kiocb *req); void io_req_tw_post_queue(struct io_kiocb *req, s32 res, u32 cflags); void io_req_task_queue(struct io_kiocb *req); void io_queue_iowq(struct io_kiocb *req, bool *dont_use); diff --git a/io_uring/rw.c b/io_uring/rw.c index 9166d8166b82..caf72f50c341 100644 --- a/io_uring/rw.c +++ b/io_uring/rw.c @@ -215,7 +215,7 @@ static void io_complete_rw(struct kiocb *kiocb, long = res) return; io_req_set_res(req, res, 0); req->io_task_work.func =3D io_req_task_complete; - io_req_task_prio_work_add(req); + io_req_task_work_add(req); } =20 static void io_complete_rw_iopoll(struct kiocb *kiocb, long res) diff --git a/io_uring/tctx.c b/io_uring/tctx.c index 9b30fb0d3603..7a68ba9beec3 100644 --- a/io_uring/tctx.c +++ b/io_uring/tctx.c @@ -88,7 +88,6 @@ __cold int io_uring_alloc_task_context(struct task_stru= ct *task, task->io_uring =3D tctx; spin_lock_init(&tctx->task_lock); INIT_WQ_LIST(&tctx->task_list); - INIT_WQ_LIST(&tctx->prio_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 dead0ed00429..c8566ea5dca4 100644 --- a/io_uring/tctx.h +++ b/io_uring/tctx.h @@ -22,7 +22,6 @@ struct io_uring_task { spinlock_t task_lock; bool task_running; struct io_wq_work_list task_list; - struct io_wq_work_list prio_task_list; struct callback_head task_work; } ____cacheline_aligned_in_smp; }; --=20 2.30.2