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 9EB85EB64D9 for ; Mon, 19 Jun 2023 11:58:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229809AbjFSL6z (ORCPT ); Mon, 19 Jun 2023 07:58:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36392 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229554AbjFSL6x (ORCPT ); Mon, 19 Jun 2023 07:58:53 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 89BDFB3 for ; Mon, 19 Jun 2023 04:58:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=oanGpIVnmNDJ42HG0BJHoWH2TaXRJrMbzL5szTBJMgg=; b=hGJgEy8kj060xYe6Pm1j1/K7ll WzLUiWXGSiFSEL5uvsajrYxFb5skntJP3xhRG7nxH+qucknA+ZQUDMvvzxwRK6HVX/Pw8sXzNNNIu LLBYTp4LQ+4Fr6myzI+w5DhUP4d+v3bxqC2Pg+Nyo03P25gdvrPiU0b3NU06YdSoXbUgt9bLQmz4g kWCQD+qbXgCk6kXiDn9YQSY1rkRyO/OWaeNt6PrqBlgq4Qnar8zjJ9rk0xNiA/loV6E8LlUdqsJ2G E8aIldL/fLcL2i/KAuZzomLFsWT/VbMvL5EtSxHaOPJxL7FSAOGm8RT7ACpLKV298oh/sak2t090V AavpKYeg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1qBDWd-00EiRH-2I; Mon, 19 Jun 2023 11:58:28 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 7E5D7300322; Mon, 19 Jun 2023 13:58:26 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 2DE9D24653290; Mon, 19 Jun 2023 13:58:26 +0200 (CEST) Date: Mon, 19 Jun 2023 13:58:26 +0200 From: Peter Zijlstra To: Cruz Zhao Cc: mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, paulmck@kernel.org, frederic@kernel.org, nsaenzju@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched/core: fix inaccurate idle stat in /proc/stat when force idle Message-ID: <20230619115826.GN4253@hirez.programming.kicks-ass.net> References: <1687107760-111340-1-git-send-email-CruzZhao@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1687107760-111340-1-git-send-email-CruzZhao@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 19, 2023 at 01:02:40AM +0800, Cruz Zhao wrote: > When force idle, rq->curr == rq->idle but rq->nr_running > 0, results > that idle_cpu() returns 0. In function tick_irq_exit(), if idle_cpu() > is 0, tick_nohz_irq_exit() will not be called, and ts->idle_active will > not become 1, which became 0 in tick_nohz_irq_enter(). > ts->idle_sleeptime won't update in function update_ts_time_stats(), if > ts->idle_active is 0, which should be 1. And this bug will result that > ts->idle_sleeptime is less than the actual value, and finally will > result that the idle time in /proc/stat is less than the actual value. > > To fix this problem, we introduce sched_core_idle_cpu(), which returns > true when force idle, and we change the judgment criteria from > idle_cpu() to sched_core_idle_cpu() in function tick_irq_exit(). > > Signed-off-by: Cruz Zhao > --- > include/linux/sched.h | 2 ++ > kernel/sched/core.c | 13 +++++++++++++ > kernel/softirq.c | 2 +- > 3 files changed, 16 insertions(+), 1 deletion(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index b09a83bfad8b..73e61c0f10a7 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -2430,9 +2430,11 @@ extern void sched_core_free(struct task_struct *tsk); > extern void sched_core_fork(struct task_struct *p); > extern int sched_core_share_pid(unsigned int cmd, pid_t pid, enum pid_type type, > unsigned long uaddr); > +extern int sched_core_idle_cpu(int cpu); > #else > static inline void sched_core_free(struct task_struct *tsk) { } > static inline void sched_core_fork(struct task_struct *p) { } > +static inline int sched_core_idle_cpu(int cpu) { return idle_cpu(cpu); } > #endif > > extern void sched_set_stop_task(int cpu, struct task_struct *stop); > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 71c1a0f232b4..c80088956987 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -7286,6 +7286,19 @@ struct task_struct *idle_task(int cpu) > return cpu_rq(cpu)->idle; > } > > +#ifdef CONFIG_SCHED_CORE > +int sched_core_idle_cpu(int cpu) > +{ > + struct rq *rq = cpu_rq(cpu); > + > + if (sched_core_enabled(rq) && rq->curr == rq->idle) > + return 1; > + > + return idle_cpu(cpu); > +} > + > +#endif > + > #ifdef CONFIG_SMP > /* > * This function computes an effective utilization for the given CPU, to be > diff --git a/kernel/softirq.c b/kernel/softirq.c > index c8a6913c067d..98b98991ce45 100644 > --- a/kernel/softirq.c > +++ b/kernel/softirq.c > @@ -630,7 +630,7 @@ static inline void tick_irq_exit(void) > int cpu = smp_processor_id(); > > /* Make sure that timer wheel updates are propagated */ > - if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { > + if ((sched_core_idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { > if (!in_hardirq()) > tick_nohz_irq_exit(); > } Urgh... did you audit all idle_cpu() users? Or so we want something like so instead? --- diff --git a/kernel/sched/core.c b/kernel/sched/core.c index a68d1276bab0..b0a1cd184b1b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7303,6 +7303,11 @@ int idle_cpu(int cpu) if (rq->curr != rq->idle) return 0; +#ifdef CONFIG_SCHED_CORE + if (sched_core_enabled() && rq->core->core_forceidle_count) + return 1; +#endif + if (rq->nr_running) return 0;