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[2620:137:e000::1:20]) by mx.google.com with ESMTP id q6-20020a17090a68c600b0021306464b66si4237532pjj.28.2022.10.27.23.43.48; Thu, 27 Oct 2022 23:44:01 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=xn4fDg49; dkim=neutral (no key) header.i=@linutronix.de header.s=2020e header.b=RQnBs+Ix; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230033AbiJ1GnH (ORCPT + 99 others); Fri, 28 Oct 2022 02:43:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52450 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229867AbiJ1GmN (ORCPT ); Fri, 28 Oct 2022 02:42:13 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9171D129755; Thu, 27 Oct 2022 23:42:11 -0700 (PDT) Date: Fri, 28 Oct 2022 06:42:08 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1666939330; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oMWKO65fY+yhjcFF62rlRZ/3VpM61mvEgbltirxSxX4=; b=xn4fDg49QwWXa7xrtaJ43r8gR0VUuQt84p22KD6gT8f5DWIJvVSxZSxPVDdxSbkQi4UdDu 8tHvZ37JgGa2iJ/dbZubdmXJ3Wm2Ge+rxeVv90HytcGbexiiBD1gyWZjWTQm9UH/xfNxCb 9ByWWOmZMJUkmOeA3Iydc1kOUcYTR83UHHpuKWdw2By/wu7S8oSyLfc4rkpBMgGkMm02a5 ZoK3SjVqUhfzUPp6WFmwxZAv6o2DikQRXSLthTMcHkx42qQXbh9xe9hhqNRef7ccQ4wAWZ ke/jgkGAnJQIC8pKz217JPN42m8gTnkovTQm4dUocE41vR822iHCJGizYiWAcQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1666939330; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oMWKO65fY+yhjcFF62rlRZ/3VpM61mvEgbltirxSxX4=; b=RQnBs+Ix56Q8xyVkZOxFjatNd3+ruzDmLxI6zxXU5rMJSZ3/lT3OuW51BrDMmm31XlSdbi fq1lO3DaFKvB8cAQ== From: "tip-bot2 for Chengming Zhou" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/psi: Fix avgs_work re-arm in psi_avgs_work() Cc: Pavan Kondeti , Chengming Zhou , "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20221010104206.12184-1-zhouchengming@bytedance.com> References: <20221010104206.12184-1-zhouchengming@bytedance.com> MIME-Version: 1.0 Message-ID: <166693932887.29415.17016910542871419770.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1746570437327161087?= X-GMAIL-MSGID: =?utf-8?q?1747912691727314920?= The following commit has been merged into the sched/core branch of tip: Commit-ID: 7d89d7bb921c5ae5a428df282e64ee5692e26fe0 Gitweb: https://git.kernel.org/tip/7d89d7bb921c5ae5a428df282e64ee5692e26fe0 Author: Chengming Zhou AuthorDate: Mon, 10 Oct 2022 18:42:06 +08:00 Committer: Peter Zijlstra CommitterDate: Thu, 27 Oct 2022 11:01:23 +02:00 sched/psi: Fix avgs_work re-arm in psi_avgs_work() Pavan reported a problem that PSI avgs_work idle shutoff is not working at all. Because PSI_NONIDLE condition would be observed in psi_avgs_work()->collect_percpu_times()->get_recent_times() even if only the kworker running avgs_work on the CPU. Although commit 1b69ac6b40eb ("psi: fix aggregation idle shut-off") avoided the ping-pong wake problem when the worker sleep, psi_avgs_work() still will always re-arm the avgs_work, so shutoff is not working. This patch changes to consider current CPU groupc as IDLE if the kworker running avgs_work is the only task running and no IOWAIT or MEMSTALL sleep tasks, in which case we will shut off the avgs_work if other CPUs' groupc are also IDLE. One potential problem is that the brief period of non-idle time incurred between the aggregation run and the kworker's dequeue will be stranded in the per-cpu buckets until avgs_work run next time. The buckets can hold 4s worth of time, and future activity will wake the avgs_work with a 2s delay, giving us 2s worth of data we can leave behind when shut off the avgs_work. If the kworker run other works after avgs_work shut off and doesn't have any scheduler activities for 2s, this maybe a problem. Reported-by: Pavan Kondeti Signed-off-by: Chengming Zhou Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20221010104206.12184-1-zhouchengming@bytedance.com --- kernel/sched/psi.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index ee2ecc0..f4cdf6f 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -242,6 +242,8 @@ static void get_recent_times(struct psi_group *group, int cpu, u32 *pchanged_states) { struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu); + int current_cpu = raw_smp_processor_id(); + bool only_avgs_work = false; u64 now, state_start; enum psi_states s; unsigned int seq; @@ -256,6 +258,15 @@ static void get_recent_times(struct psi_group *group, int cpu, memcpy(times, groupc->times, sizeof(groupc->times)); state_mask = groupc->state_mask; state_start = groupc->state_start; + /* + * This CPU has only avgs_work kworker running, snapshot the + * newest times then don't need to re-arm for this groupc. + * Normally this kworker will sleep soon and won't wake + * avgs_work back up in psi_group_change(). + */ + if (current_cpu == cpu && groupc->tasks[NR_RUNNING] == 1 && + !groupc->tasks[NR_IOWAIT] && !groupc->tasks[NR_MEMSTALL]) + only_avgs_work = true; } while (read_seqcount_retry(&groupc->seq, seq)); /* Calculate state time deltas against the previous snapshot */ @@ -280,6 +291,10 @@ static void get_recent_times(struct psi_group *group, int cpu, if (delta) *pchanged_states |= (1 << s); } + + /* Clear PSI_NONIDLE so avgs_work won't be re-armed for this groupc */ + if (only_avgs_work) + *pchanged_states &= ~(1 << PSI_NONIDLE); } static void calc_avgs(unsigned long avg[3], int missed_periods,