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 17DC0C433EF for ; Mon, 27 Jun 2022 13:36:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235927AbiF0NgO (ORCPT ); Mon, 27 Jun 2022 09:36:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44226 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234557AbiF0NgN (ORCPT ); Mon, 27 Jun 2022 09:36:13 -0400 Received: from out0.migadu.com (out0.migadu.com [IPv6:2001:41d0:2:267::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 578A06362 for ; Mon, 27 Jun 2022 06:36:12 -0700 (PDT) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1656336971; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RniOcn9yPuvipwzwt28WCa9KHB7H+Sp1eVey/+p4yNE=; b=eRtI2NderyvAJesaCu69Ue46FrYS91bh7OZep2B5GUS7Sa3LN0gkMC7Frt992WxedDionK QpKjh4NK60esrY750ooCRCtG1U6M3Y+CkErRU3lSNdcPNf6lHu5y1HgXRpvqj3jumbvfiE gbaQ0G9qmB7Ae1RTDJbKYpT5AqRRxGY= From: Hao Xu To: io-uring@vger.kernel.org Cc: Jens Axboe , Pavel Begunkov Subject: [PATCH 07/11] io-wq: implement fixed worker logic Date: Mon, 27 Jun 2022 21:35:37 +0800 Message-Id: <20220627133541.15223-8-hao.xu@linux.dev> In-Reply-To: <20220627133541.15223-1-hao.xu@linux.dev> References: <20220627133541.15223-1-hao.xu@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org From: Hao Xu The current implementation of io-wq has big spinlock contension. The main reason is the single work list model. All producers(who insert works) and consumers(io-workers) have to grap wqe->lock to move ahead. Set max_worker to 3 or 4, do a fio read test, we can see 40%~50% lock contension. Introduce fixed io-workers which sticks there to handle works and have their own work list. previous: producer0 ---insert---> work_list ---get---> io-worker0,1,2 now: ---> private work_list0 --get--> fixed-worker0 / producer0 --insert----> private work_list1 --get--> fixed-worker1 | \ | ---> private work_list2 --get--> fixed-worker2 | |---insert---> public work_list --get--> (normal)io-worker Since each fixed-worker has a private work list, the contension will be limited to a smaller range(the private work list). Logic of fixed-worker: first handle private works then public ones. Logic of normal io-worker: only handle public works. Logic of producer: 1) randomly pick a private work list and check if it is full, insert the work if it's not 2) insert the work to the public work list if 1) fails. The get logic of a private list: fixed-worker grab all the works in its private work list(like what tctx_task_work() does) rather than one by one.(this code is in the next patches as a optimization) To achieve this, we need to add an io_wqe_acct for each fixed-worker struct, and though this we can leverage the old code as much as possible, which makes the new design clean and compatible. Good things of this feature: 1) bound and unbound work lists now have different spinlocks. 2) much smaller contension between work producers and consumers. 3) fixed workers are friendly for users to control: binding cpus, reset priority etc. Wrote a nop test program to test it, 3 fixed-workers VS 3 normal workers. normal workers: ./run_nop_wqe.sh nop_wqe_normal 200000 100 3 1-3 time spent: 17314274 usecs IOPS: 1155116 time spent: 17016942 usecs IOPS: 1175299 time spent: 17908684 usecs IOPS: 1116776 fixed workers: ./run_nop_wqe.sh nop_wqe_fixed 200000 100 3 1-3 time spent: 10464397 usecs IOPS: 1911242 time spent: 9610976 usecs IOPS: 2080954 time spent: 9807361 usecs IOPS: 2039284 About 2x improvement. From perf result, almost no acct->lock contension. Test program: https://github.com/HowHsu/liburing/tree/fixed_worker Signed-off-by: Hao Xu --- io_uring/io-wq.c | 148 ++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 122 insertions(+), 26 deletions(-) diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c index 11fe5787c409..c87ba38f27b1 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -71,6 +71,7 @@ struct io_wqe_acct { unsigned nr_works; }; unsigned max_works; + unsigned work_seq; union { struct io_wq_work_list work_list; struct { @@ -629,9 +630,9 @@ static void io_assign_current_work(struct io_worker *worker, static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work); -static void io_worker_handle_work(struct io_worker *worker) +static void io_worker_handle_work(struct io_worker *worker, + struct io_wqe_acct *acct) { - struct io_wqe_acct *acct = io_wqe_get_acct(worker); struct io_wqe *wqe = worker->wqe; struct io_wq *wq = wqe->wq; bool do_kill = test_bit(IO_WQ_BIT_EXIT, &wq->state); @@ -703,19 +704,31 @@ static void io_worker_handle_work(struct io_worker *worker) } while (1); } +static inline void io_worker_handle_private_work(struct io_worker *worker) +{ + io_worker_handle_work(worker, &worker->acct); +} + +static inline void io_worker_handle_public_work(struct io_worker *worker) +{ + io_worker_handle_work(worker, io_wqe_get_acct(worker)); +} + static int io_wqe_worker(void *data) { struct io_worker *worker = data; - struct io_wqe_acct *acct = io_wqe_get_acct(worker); struct io_wqe *wqe = worker->wqe; struct io_wq *wq = wqe->wq; - bool last_timeout = false; + struct io_wqe_acct *acct = + io_get_acct(wqe, worker->flags & IO_WORKER_F_BOUND, false); bool fixed = worker->flags & IO_WORKER_F_FIXED; + bool last_timeout = false; char buf[TASK_COMM_LEN]; worker->flags |= (IO_WORKER_F_UP | IO_WORKER_F_RUNNING); - snprintf(buf, sizeof(buf), "iou-wrk-%d", wq->task->pid); + snprintf(buf, sizeof(buf), fixed ? "iou-fix-%d" : "iou-wrk-%d", + wq->task->pid); set_task_comm(current, buf); audit_alloc_kernel(current); @@ -727,13 +740,24 @@ static int io_wqe_worker(void *data) break; set_current_state(TASK_INTERRUPTIBLE); - while (!(worker->flags & IO_WORKER_F_EXIT) && - io_acct_run_queue(acct)) - io_worker_handle_work(worker); - + if (fixed) { + while (io_acct_run_queue(&worker->acct)) + io_worker_handle_private_work(worker); + if (io_acct_run_queue(acct)) + io_worker_handle_public_work(worker); + } else { + while (io_acct_run_queue(acct)) + io_worker_handle_public_work(worker); + } raw_spin_lock(&wqe->lock); - /* timed out, exit unless we're the last worker */ - if (last_timeout && acct->nr_workers > 1) { + /* timed out, a worker will exit only if: + * - not a fixed worker + * - not the last non-fixed worker + * + * the second condition is due to we need at least one worker to + * handle the public work list. + */ + if (last_timeout && !fixed && acct->nr_workers > 1) { acct->nr_workers--; raw_spin_unlock(&wqe->lock); __set_current_state(TASK_RUNNING); @@ -759,10 +783,18 @@ static int io_wqe_worker(void *data) last_timeout = !ret; } - if (test_bit(IO_WQ_BIT_EXIT, &wq->state)) - io_worker_handle_work(worker); - if (fixed) + if (test_bit(IO_WQ_BIT_EXIT, &wq->state) && !fixed) + io_worker_handle_public_work(worker); + if (fixed) { io_fixed_worker_exit(worker); + /* + * Check and handle private work list again + * to avoid race with private work insertion + * TODO: an alternative way is to deliver + * works to the public work list + */ + io_worker_handle_private_work(worker); + } audit_free(current); io_worker_exit(worker); @@ -1006,9 +1038,9 @@ static void io_run_cancel(struct io_wq_work *work, struct io_wqe *wqe) } while (work); } -static void io_wqe_insert_work(struct io_wqe *wqe, struct io_wq_work *work) +static void io_wqe_insert_work(struct io_wqe *wqe, struct io_wq_work *work, + struct io_wqe_acct *acct) { - struct io_wqe_acct *acct = io_work_get_acct(wqe, work); unsigned int hash; struct io_wq_work *tail; @@ -1027,6 +1059,45 @@ static void io_wqe_insert_work(struct io_wqe *wqe, struct io_wq_work *work) wq_list_add_after(&work->list, &tail->list, &acct->work_list); } +static bool io_wqe_insert_private_work(struct io_wqe *wqe, + struct io_wq_work *work, + struct io_wqe_acct *acct) +{ + unsigned int nr_fixed; + struct io_worker *fixed_worker; + struct io_wqe_acct *iw_acct; + unsigned int fixed_worker_index; + + raw_spin_lock(&acct->lock); + nr_fixed = acct->nr_fixed; + if (!nr_fixed) { + raw_spin_unlock(&acct->lock); + return false; + } + + fixed_worker_index = (acct->work_seq++) % nr_fixed; + fixed_worker = acct->fixed_workers[fixed_worker_index]; + if (!fixed_worker || fixed_worker->flags & IO_WORKER_F_EXIT) { + raw_spin_unlock(&acct->lock); + return false; + } + iw_acct = &fixed_worker->acct; + + raw_spin_lock(&iw_acct->lock); + if (iw_acct->nr_works < iw_acct->max_works) { + io_wqe_insert_work(wqe, work, iw_acct); + iw_acct->nr_works++; + raw_spin_unlock(&iw_acct->lock); + wake_up_process(fixed_worker->task); + raw_spin_unlock(&acct->lock); + return true; + } + raw_spin_unlock(&iw_acct->lock); + raw_spin_unlock(&acct->lock); + + return false; +} + static bool io_wq_work_match_item(struct io_wq_work *work, void *data) { return work == data; @@ -1035,6 +1106,7 @@ static bool io_wq_work_match_item(struct io_wq_work *work, void *data) static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work) { struct io_wqe_acct *acct = io_work_get_acct(wqe, work); + struct io_wqe_acct *fixed_acct; struct io_cb_cancel_data match; unsigned work_flags = work->flags; bool do_create; @@ -1049,8 +1121,14 @@ static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work) return; } + fixed_acct = io_get_acct(wqe, !acct->index, true); + if (fixed_acct->fixed_worker_registered && !io_wq_is_hashed(work)) { + if (io_wqe_insert_private_work(wqe, work, fixed_acct)) + return; + } + raw_spin_lock(&acct->lock); - io_wqe_insert_work(wqe, work); + io_wqe_insert_work(wqe, work, acct); clear_bit(IO_ACCT_STALLED_BIT, &acct->flags); raw_spin_unlock(&acct->lock); @@ -1136,9 +1214,9 @@ static bool io_wq_worker_cancel(struct io_worker *worker, void *data) static inline void io_wqe_remove_pending(struct io_wqe *wqe, struct io_wq_work *work, - struct io_wq_work_node *prev) + struct io_wq_work_node *prev, + struct io_wqe_acct *acct) { - struct io_wqe_acct *acct = io_work_get_acct(wqe, work); unsigned int hash = io_get_work_hash(work); struct io_wq_work *prev_work = NULL; @@ -1165,7 +1243,7 @@ static bool io_acct_cancel_pending_work(struct io_wqe *wqe, work = container_of(node, struct io_wq_work, list); if (!match->fn(work, match->data)) continue; - io_wqe_remove_pending(wqe, work, prev); + io_wqe_remove_pending(wqe, work, prev, acct); raw_spin_unlock(&acct->lock); io_run_cancel(work, wqe); match->nr_pending++; @@ -1180,17 +1258,35 @@ static bool io_acct_cancel_pending_work(struct io_wqe *wqe, static void io_wqe_cancel_pending_work(struct io_wqe *wqe, struct io_cb_cancel_data *match) { - int i; -retry: - for (i = 0; i < IO_WQ_ACCT_NR; i++) { - struct io_wqe_acct *acct = io_get_acct(wqe, i == 0, false); + int i, j; + struct io_wqe_acct *acct, *iw_acct; +retry_public: + for (i = 0; i < IO_WQ_ACCT_NR; i++) { + acct = io_get_acct(wqe, i == 0, false); if (io_acct_cancel_pending_work(wqe, acct, match)) { if (match->cancel_all) - goto retry; - break; + goto retry_public; + return; } } + +retry_private: + for (i = 0; i < IO_WQ_ACCT_NR; i++) { + acct = io_get_acct(wqe, i == 0, true); + raw_spin_lock(&acct->lock); + for (j = 0; j < acct->nr_fixed; j++) { + iw_acct = &acct->fixed_workers[j]->acct; + if (io_acct_cancel_pending_work(wqe, iw_acct, match)) { + if (match->cancel_all) { + raw_spin_unlock(&acct->lock); + goto retry_private; + } + break; + } + } + raw_spin_unlock(&acct->lock); + } } static void io_wqe_cancel_running_work(struct io_wqe *wqe, -- 2.25.1