From patchwork Fri Sep 13 22:28:01 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Begunkov X-Patchwork-Id: 11145447 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7942013BD for ; Fri, 13 Sep 2019 22:28:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5050F20692 for ; Fri, 13 Sep 2019 22:28:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="kbmST97n" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404107AbfIMW2X (ORCPT ); Fri, 13 Sep 2019 18:28:23 -0400 Received: from mail-wm1-f68.google.com ([209.85.128.68]:52346 "EHLO mail-wm1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404009AbfIMW2W (ORCPT ); Fri, 13 Sep 2019 18:28:22 -0400 Received: by mail-wm1-f68.google.com with SMTP id x2so4210994wmj.2; Fri, 13 Sep 2019 15:28:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=cGeuD+sEgwestY+QfSRqtVae+dkCrd0C5Kw6xlGoBtE=; b=kbmST97n7ifZMIxFSMVWHNUEVbHqYHj+S4/C5TXxaToLekOmg77nd9nxP2FBjEbJCW tpSpPyVsOtihQBylK+i5dGQE9678Qf+MZsCbg+FteZrDhF3/pYO0tmloOm1jwjZEzSMX GG8CtWMJvxxFTmMIDF2hB45CnruwG9pemPXeJPM97HF743BNP19/VqUijJpRLMhnvECc UQ6e7thbyCpJ0g44DD0l+AF7XUEncay/LUvo4m6Zagx6RiFd5kdZTFYlSXlfJLIhZYgQ s/Cwwf0+qcgE2lpn7BMOTV+Fpo/OcvRawFn4IjO3GT75qEDNhCAMgSNOlkAaVwujcfXF cx7A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=cGeuD+sEgwestY+QfSRqtVae+dkCrd0C5Kw6xlGoBtE=; b=I4ycINbV7vKC20qPI813/xWHYB3hSdhjDzSDzu8qUrLrinhteYxrjtMn1Fmxr91HJb pTSTb0aCQxF+3RRmUOyU4JC2NHDcLR27hOyGgmhBionN/CMsmpXUfxgu1kKa+JP0kD6U OzWwQmUvsiaxQ4SzM52Xacw1Tlfx0p888jxzBFubEYCnkJB2nTYeik1C2r1Kqyrajpxo NhNZRQ7R7133knxitzvfl9fKy8seuUQkhJgDqDg7G1w3bfDBUgZHZfOfcjFm81nLGuI/ V8FPNo3rcmhG8yZA+VB0iX8fvCxnnzvh2gEmrDn8jJuTMR/oHYLX0jLhiYc+byXeMtnx RRrg== X-Gm-Message-State: APjAAAVZO9xGYt2tQVFFX6Ee0P85htBVDDMQYePk9Q4FeWPPwKgbxP7L wZ6vBhY5GkAZuCphnWQ/+qYz2oRVbYg= X-Google-Smtp-Source: APXvYqy8wrJ5nhJ4PwoPi14LXd7kudFuNh2fo7MKgGVQO+mgZKr7jU+djcW1+hX+Alap/nDwyR1ZDQ== X-Received: by 2002:a1c:5f0b:: with SMTP id t11mr5084171wmb.76.1568413699029; Fri, 13 Sep 2019 15:28:19 -0700 (PDT) Received: from localhost.localdomain ([109.126.151.137]) by smtp.gmail.com with ESMTPSA id d12sm3456107wme.33.2019.09.13.15.28.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Sep 2019 15:28:18 -0700 (PDT) From: "Pavel Begunkov (Silence)" To: Jens Axboe , Ingo Molnar , Peter Zijlstra , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Pavel Begunkov Subject: [RFC PATCH 1/2] sched/wait: Add wait_threshold Date: Sat, 14 Sep 2019 01:28:01 +0300 Message-Id: X-Mailer: git-send-email 2.22.0 In-Reply-To: References: MIME-Version: 1.0 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Pavel Begunkov Add wait_threshold -- a custom wait_event derivative, that waits until a value is equal to or greater than the specified threshold. Signed-off-by: Pavel Begunkov --- include/linux/wait_threshold.h | 64 ++++++++++++++++++++++++++++++++++ kernel/sched/Makefile | 2 +- kernel/sched/wait_threshold.c | 26 ++++++++++++++ 3 files changed, 91 insertions(+), 1 deletion(-) create mode 100644 include/linux/wait_threshold.h create mode 100644 kernel/sched/wait_threshold.c diff --git a/include/linux/wait_threshold.h b/include/linux/wait_threshold.h new file mode 100644 index 000000000000..01798c3aae1f --- /dev/null +++ b/include/linux/wait_threshold.h @@ -0,0 +1,64 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_WAIT_THRESHOLD_H +#define _LINUX_WAIT_THRESHOLD_H + +#include + +struct wait_threshold_queue_entry { + struct wait_queue_entry wq_entry; + unsigned int threshold; +}; + +void init_wait_threshold_entry(struct wait_threshold_queue_entry *wtq_entry, + unsigned int threshold); + +static inline void wake_up_threshold(struct wait_queue_head *wq_head, + unsigned int val) +{ + void *arg = (void *)(unsigned long)val; + + __wake_up(wq_head, TASK_NORMAL, 1, arg); +} + +#define ___wait_threshold_event(q, thresh, condition, state, \ + exclusive, ret, cmd) \ +({ \ + __label__ __out; \ + struct wait_queue_head *__wq_head = &q; \ + struct wait_threshold_queue_entry __wtq_entry; \ + struct wait_queue_entry *__wq_entry = &__wtq_entry.wq_entry; \ + long __ret = ret; /* explicit shadow */ \ + \ + init_wait_threshold_entry(&__wtq_entry, thresh); \ + for (;;) { \ + long __int = prepare_to_wait_event(__wq_head, \ + __wq_entry, \ + state); \ + if (condition) \ + break; \ + \ + if (___wait_is_interruptible(state) && __int) { \ + __ret = __int; \ + goto __out; \ + } \ + \ + cmd; \ + } \ + finish_wait(__wq_head, __wq_entry); \ +__out: __ret; \ +}) + +#define __wait_threshold_interruptible(q, thresh, condition) \ + ___wait_threshold_event(q, thresh, condition, TASK_INTERRUPTIBLE, 0, 0,\ + schedule()) + +#define wait_threshold_interruptible(q, threshold, val) \ +({ \ + int __ret = 0; \ + might_sleep(); \ + if ((val) < (threshold)) \ + __ret = __wait_threshold_interruptible(q, \ + threshold, ((val) >= (threshold))); \ + __ret; \ +}) +#endif /* _LINUX_WAIT_THRESHOLD_H */ diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile index 21fb5a5662b5..bb895a3184f9 100644 --- a/kernel/sched/Makefile +++ b/kernel/sched/Makefile @@ -18,7 +18,7 @@ endif obj-y += core.o loadavg.o clock.o cputime.o obj-y += idle.o fair.o rt.o deadline.o -obj-y += wait.o wait_bit.o swait.o completion.o +obj-y += wait.o wait_bit.o wait_threshold.o swait.o completion.o obj-$(CONFIG_SMP) += cpupri.o cpudeadline.o topology.o stop_task.o pelt.o obj-$(CONFIG_SCHED_AUTOGROUP) += autogroup.o diff --git a/kernel/sched/wait_threshold.c b/kernel/sched/wait_threshold.c new file mode 100644 index 000000000000..80a027c02ff3 --- /dev/null +++ b/kernel/sched/wait_threshold.c @@ -0,0 +1,26 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include "sched.h" +#include + +static int wake_threshold_function(struct wait_queue_entry *wq_entry, + unsigned int mode, int sync, void *arg) +{ + unsigned int val = (unsigned int)(unsigned long)arg; + struct wait_threshold_queue_entry *wtq_entry = + container_of(wq_entry, struct wait_threshold_queue_entry, + wq_entry); + + if (val < wtq_entry->threshold) + return 0; + + return default_wake_function(wq_entry, mode, sync, arg); +} + +void init_wait_threshold_entry(struct wait_threshold_queue_entry *wtq_entry, + unsigned int threshold) +{ + init_wait_entry(&wtq_entry->wq_entry, 0); + wtq_entry->wq_entry.func = wake_threshold_function; + wtq_entry->threshold = threshold; +} +EXPORT_SYMBOL(init_wait_threshold_entry); From patchwork Fri Sep 13 22:28:02 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Begunkov X-Patchwork-Id: 11145445 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id ACBBC13BD for ; Fri, 13 Sep 2019 22:28:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 827BB206A5 for ; Fri, 13 Sep 2019 22:28:23 +0000 (UTC) Authentication-Results: mail.kernel.org; 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Fri, 13 Sep 2019 15:28:20 -0700 (PDT) From: "Pavel Begunkov (Silence)" To: Jens Axboe , Ingo Molnar , Peter Zijlstra , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Pavel Begunkov Subject: [RFC PATCH 2/2] io_uring: Optimise cq waiting with wait_threshold Date: Sat, 14 Sep 2019 01:28:02 +0300 Message-Id: <71aa08dfd7fee3093845957cdcf32b21f9194892.1568413210.git.asml.silence@gmail.com> X-Mailer: git-send-email 2.22.0 In-Reply-To: References: MIME-Version: 1.0 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org From: Pavel Begunkov While waiting for completion events in io_cqring_wait(), the process will be waken up inside wait_threshold_interruptible() on any request completion, check num of events in completion queue and potentially go to sleep again. Apparently, there could be a lot of such spurious wakeups with lots of overhead. It especially manifests itself, when min_events is large, and completions are arriving one by one or in small batches (that usually is true). E.g. if device completes requests one by one and io_uring_enter is waiting for 100 events, then there will be ~99 spurious wakeups. Use new wait_threshold_*() instead, which won't wake it up until necessary number of events is collected. Performance test: The first thread generates requests (QD=512) one by one, so they will be completed in the similar pattern. The second thread waiting for 128 events to complete. Tested with null_blk with 5us delay and 3.8GHz Intel CPU. throughput before: 270 KIOPS throughput after: 370 KIOPS So, ~40% throughput boost on this exaggerate test. Signed-off-by: Pavel Begunkov --- fs/io_uring.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 37395208a729..17d2d30b763a 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -70,6 +70,7 @@ #include #include #include +#include #include @@ -403,6 +404,13 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p) return ctx; } +static unsigned int io_cqring_events(struct io_rings *rings) +{ + /* See comment at the top of this file */ + smp_rmb(); + return READ_ONCE(rings->cq.tail) - READ_ONCE(rings->cq.head); +} + static inline bool io_sequence_defer(struct io_ring_ctx *ctx, struct io_kiocb *req) { @@ -521,7 +529,7 @@ static void io_cqring_fill_event(struct io_ring_ctx *ctx, u64 ki_user_data, static void io_cqring_ev_posted(struct io_ring_ctx *ctx) { if (waitqueue_active(&ctx->wait)) - wake_up(&ctx->wait); + wake_up_threshold(&ctx->wait, io_cqring_events(ctx->rings)); if (waitqueue_active(&ctx->sqo_wait)) wake_up(&ctx->sqo_wait); if (ctx->cq_ev_fd) @@ -546,7 +554,7 @@ static void io_ring_drop_ctx_refs(struct io_ring_ctx *ctx, unsigned refs) percpu_ref_put_many(&ctx->refs, refs); if (waitqueue_active(&ctx->wait)) - wake_up(&ctx->wait); + wake_up_threshold(&ctx->wait, io_cqring_events(ctx->rings)); } static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx, @@ -681,12 +689,6 @@ static void io_put_req(struct io_kiocb *req) io_free_req(req); } -static unsigned io_cqring_events(struct io_rings *rings) -{ - /* See comment at the top of this file */ - smp_rmb(); - return READ_ONCE(rings->cq.tail) - READ_ONCE(rings->cq.head); -} /* * Find and free completed poll iocbs @@ -2591,7 +2593,8 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, return ret; } - ret = wait_event_interruptible(ctx->wait, io_cqring_events(rings) >= min_events); + ret = wait_threshold_interruptible(ctx->wait, min_events, + io_cqring_events(rings)); restore_saved_sigmask_unless(ret == -ERESTARTSYS); if (ret == -ERESTARTSYS) ret = -EINTR;