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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 E6B38C3F2D1 for ; Thu, 5 Mar 2020 08:17:03 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A7CB82073D for ; Thu, 5 Mar 2020 08:17:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="OJAcJ+LO" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A7CB82073D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=rock-chips.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=Pt5/JGZAO5YbNxfxRLMRMmfwQx2td/6PpqP/bKuprmw=; b=OJAcJ+LOzl8OZldvwIgcTEtNzO gFSW+LtclTYenJ1zePQX8y8MpLWn3wSQqYsYx+PCNHfxS7mZ5xhSaWK3cFeELZASw0nNUB9GB59OK utrZuWlKkO/OVXWDZaQb62ONJ9adMqlBRKpFrIKVpukBkSrYRrKrmjW4naAWmm8/qmFd6KHX3A3Cz K+qhCp4NpM4iklsfSuylTPIBJkeOdqkcM9S4XXG1rVNfWtrc2iUkd7uNOvLGM2GGHqncPRu7icwh+ qvWVp/CRxwm8H9jwYBpyRMIBeJjRRDOIq8r5dxUhxOtlu/WAEkO6vc7LyUPOqUyddcpx5FkWMvf38 20f2DBDQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j9lgk-0003Xn-Ud; Thu, 05 Mar 2020 08:17:02 +0000 Received: from lucky1.263xmail.com ([211.157.147.133]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1j9lgf-0003RL-9a for linux-arm-kernel@lists.infradead.org; Thu, 05 Mar 2020 08:16:59 +0000 Received: from localhost (unknown [192.168.167.209]) by lucky1.263xmail.com (Postfix) with ESMTP id 3A7D89F87B; Thu, 5 Mar 2020 16:16:34 +0800 (CST) X-MAIL-GRAY: 0 X-MAIL-DELIVERY: 1 X-ADDR-CHECKED4: 1 X-ANTISPAM-LEVEL: 2 X-ABS-CHECKED: 0 Received: from localhost.localdomain (unknown [58.22.7.114]) by smtp.263.net (postfix) whith ESMTP id P32633T140274034538240S1583396184137610_; Thu, 05 Mar 2020 16:16:33 +0800 (CST) X-IP-DOMAINF: 1 X-UNIQUE-TAG: <104baa6c45971adc002ce26f794e2d59> X-RL-SENDER: cl@rock-chips.com X-SENDER: cl@rock-chips.com X-LOGIN-NAME: cl@rock-chips.com X-FST-TO: heiko@sntech.de X-SENDER-IP: 58.22.7.114 X-ATTACHMENT-NUM: 0 X-DNS-TYPE: 0 X-System-Flag: 0 From: To: heiko@sntech.de Subject: [PATCH v1 1/1] sched/fair: do not preempt current task if it is going to call schedule() Date: Thu, 5 Mar 2020 16:16:11 +0800 Message-Id: <20200305081611.29323-2-cl@rock-chips.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200305081611.29323-1-cl@rock-chips.com> References: <20200305081611.29323-1-cl@rock-chips.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200305_001657_823891_F0466034 X-CRM114-Status: GOOD ( 16.19 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: juri.lelli@redhat.com, mark.rutland@arm.com, geert+renesas@glider.be, peterz@infradead.org, catalin.marinas@arm.com, bsegall@google.com, will@kernel.org, mpe@ellerman.id.au, linux@armlinux.org.uk, dietmar.eggemann@arm.com, ben.dooks@codethink.co.uk, mgorman@suse.de, Liang Chen , huangtao@rock-chips.com, keescook@chromium.org, anshuman.khandual@arm.com, rostedt@goodmis.org, tglx@linutronix.de, surenb@google.com, mingo@redhat.com, allison@lohutok.net, linux-arm-kernel@lists.infradead.org, wad@chromium.org, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, luto@amacapital.net, george_davis@mentor.com, sudeep.holla@arm.com, akpm@linux-foundation.org, info@metux.net, kstewart@linuxfoundation.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Liang Chen when we create a kthread with ktrhead_create_on_cpu(),the child thread entry is ktread.c:ktrhead() which will be preempted by the parent after call complete(done) while schedule() is not called yet,then the parent will call wait_task_inactive(child) but the child is still on the runqueue, so the parent will schedule_hrtimeout() for 1 jiffy,it will waste a lot of time,especially on startup. parent child ktrhead_create_on_cpu() wait_fo_completion(&done) -----> ktread.c:ktrhead() |----- complete(done);--wakeup and preempted by parent kthread_bind() <------------| |-> schedule();--dequeue here wait_task_inactive(child) | schedule_hrtimeout(1 jiffy) -| So we hope the child just wakeup parent but not preempted by parent, and the child is going to call schedule() soon,then the parent will not call schedule_hrtimeout(1 jiffy) as the child is already dequeue. The same issue for ktrhead_park()&&kthread_parkme(). This patch can save 120ms on rk312x startup with CONFIG_HZ=300. Signed-off-by: Liang Chen --- arch/arm/include/asm/thread_info.h | 1 + arch/arm64/include/asm/thread_info.h | 1 + include/linux/sched.h | 15 +++++++++++++++ kernel/kthread.c | 4 ++++ kernel/sched/fair.c | 4 ++++ 5 files changed, 25 insertions(+) diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h index 0d0d5178e2c3..51802991ba1f 100644 --- a/arch/arm/include/asm/thread_info.h +++ b/arch/arm/include/asm/thread_info.h @@ -145,6 +145,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp *, #define TIF_USING_IWMMXT 17 #define TIF_MEMDIE 18 /* is terminating due to OOM killer */ #define TIF_RESTORE_SIGMASK 20 +#define TIF_GOING_TO_SCHED 27 /* task is going to call schedule() */ #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index f0cec4160136..332786f11dc3 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -78,6 +78,7 @@ void arch_release_task_struct(struct task_struct *tsk); #define TIF_SVE_VL_INHERIT 24 /* Inherit sve_vl_onexec across exec */ #define TIF_SSBD 25 /* Wants SSB mitigation */ #define TIF_TAGGED_ADDR 26 /* Allow tagged user addresses */ +#define TIF_GOING_TO_SCHED 27 /* task is going to call schedule() */ #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) diff --git a/include/linux/sched.h b/include/linux/sched.h index 04278493bf15..cb9058d2cf0b 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1768,6 +1768,21 @@ static inline int test_tsk_need_resched(struct task_struct *tsk) return unlikely(test_tsk_thread_flag(tsk,TIF_NEED_RESCHED)); } +static inline void set_tsk_going_to_sched(struct task_struct *tsk) +{ + set_tsk_thread_flag(tsk, TIF_GOING_TO_SCHED); +} + +static inline void clear_tsk_going_to_sched(struct task_struct *tsk) +{ + clear_tsk_thread_flag(tsk, TIF_GOING_TO_SCHED); +} + +static inline int test_tsk_going_to_sched(struct task_struct *tsk) +{ + return unlikely(test_tsk_thread_flag(tsk, TIF_GOING_TO_SCHED)); +} + /* * cond_resched() and cond_resched_lock(): latency reduction via * explicit rescheduling in places that are safe. The return diff --git a/kernel/kthread.c b/kernel/kthread.c index b262f47046ca..8a4e4c9cdc22 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -199,8 +199,10 @@ static void __kthread_parkme(struct kthread *self) if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags)) break; + set_tsk_going_to_sched(current); complete(&self->parked); schedule(); + clear_tsk_going_to_sched(current); } __set_current_state(TASK_RUNNING); } @@ -245,8 +247,10 @@ static int kthread(void *_create) /* OK, tell user we're spawned, wait for stop or wakeup */ __set_current_state(TASK_UNINTERRUPTIBLE); create->result = current; + set_tsk_going_to_sched(current); complete(done); schedule(); + clear_tsk_going_to_sched(current); ret = -EINTR; if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) { diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3c8a379c357e..28a308743bf8 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4330,6 +4330,8 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) hrtimer_active(&rq_of(cfs_rq)->hrtick_timer)) return; #endif + if (test_tsk_going_to_sched(rq_of(cfs_rq)->curr)) + return; if (cfs_rq->nr_running > 1) check_preempt_tick(cfs_rq, curr); @@ -6633,6 +6635,8 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ */ if (test_tsk_need_resched(curr)) return; + if (test_tsk_going_to_sched(curr)) + return; /* Idle tasks are by definition preempted by non-idle tasks. */ if (unlikely(task_has_idle_policy(curr)) && -- 2.17.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel