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=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 9C8F9C07E94 for ; Fri, 4 Jun 2021 13:38:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7E8C2613FE for ; Fri, 4 Jun 2021 13:38:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230313AbhFDNki (ORCPT ); Fri, 4 Jun 2021 09:40:38 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:53474 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230284AbhFDNkh (ORCPT ); Fri, 4 Jun 2021 09:40:37 -0400 Date: Fri, 04 Jun 2021 13:38:49 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1622813930; 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=WyczKmVahFC47ZS/saZxFVYFQaqkx7u6zwKUlvUxo7o=; b=eGaZM4ZQI8L+ZiouJOiBHN2fVqiZmqGJoum0aeUv+QootDmJFSVXKQuwgKRXaWOblQ6sSu F0SdlFCU1O70VayWKWtb55KvkPxJLxVgVSJSwEOtLZd3+DDqGvlTX1CeqnNVwS6LC7iUH8 KU24wPOM0V7mEFJAelOl4w38/9h5d2fquT1bRZ3gPw3QuSQ8lyWtYMku/x6r8VYeZGdK+s cuZrcC4K8pOD3AkT9L3UawoMydTtt0H8gzB1RcsWwI5wEBXXAjqDGLxbxmA1Vq23ofEmZJ LZe6i12sr3NO/Tl1gpl0PVb0CaJxVtsdSS7icJqmaisgBGPE1Eq3NiI6lwZZdA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1622813930; 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=WyczKmVahFC47ZS/saZxFVYFQaqkx7u6zwKUlvUxo7o=; b=p4YvCWfZ41uiWgi19amVpMEGO7ZB2fY2UB5TYbbCMxmB+ZaRcNpbyZeqwoB1sK7ZKit2rG UTOmBBXN7on8WKAQ== From: "tip-bot2 for Dietmar Eggemann" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/urgent] sched/fair: Fix util_est UTIL_AVG_UNCHANGED handling Cc: Dietmar Eggemann , "Peter Zijlstra (Intel)" , Xuewen Yan , Vincent Donnefort , Vincent Guittot , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210602145808.1562603-1-dietmar.eggemann@arm.com> References: <20210602145808.1562603-1-dietmar.eggemann@arm.com> MIME-Version: 1.0 Message-ID: <162281392953.29796.486453710675011021.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/urgent branch of tip: Commit-ID: 68d7a190682aa4eb02db477328088ebad15acc83 Gitweb: https://git.kernel.org/tip/68d7a190682aa4eb02db477328088ebad15acc83 Author: Dietmar Eggemann AuthorDate: Wed, 02 Jun 2021 16:58:08 +02:00 Committer: Peter Zijlstra CommitterDate: Thu, 03 Jun 2021 15:47:23 +02:00 sched/fair: Fix util_est UTIL_AVG_UNCHANGED handling The util_est internal UTIL_AVG_UNCHANGED flag which is used to prevent unnecessary util_est updates uses the LSB of util_est.enqueued. It is exposed via _task_util_est() (and task_util_est()). Commit 92a801e5d5b7 ("sched/fair: Mask UTIL_AVG_UNCHANGED usages") mentions that the LSB is lost for util_est resolution but find_energy_efficient_cpu() checks if task_util_est() returns 0 to return prev_cpu early. _task_util_est() returns the max value of util_est.ewma and util_est.enqueued or'ed w/ UTIL_AVG_UNCHANGED. So task_util_est() returning the max of task_util() and _task_util_est() will never return 0 under the default SCHED_FEAT(UTIL_EST, true). To fix this use the MSB of util_est.enqueued instead and keep the flag util_est internal, i.e. don't export it via _task_util_est(). The maximal possible util_avg value for a task is 1024 so the MSB of 'unsigned int util_est.enqueued' isn't used to store a util value. As a caveat the code behind the util_est_se trace point has to filter UTIL_AVG_UNCHANGED to see the real util_est.enqueued value which should be easy to do. This also fixes an issue report by Xuewen Yan that util_est_update() only used UTIL_AVG_UNCHANGED for the subtrahend of the equation: last_enqueued_diff = ue.enqueued - (task_util() | UTIL_AVG_UNCHANGED) Fixes: b89997aa88f0b sched/pelt: Fix task util_est update filtering Signed-off-by: Dietmar Eggemann Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Xuewen Yan Reviewed-by: Vincent Donnefort Reviewed-by: Vincent Guittot Link: https://lore.kernel.org/r/20210602145808.1562603-1-dietmar.eggemann@arm.com --- include/linux/sched.h | 8 ++++++++ kernel/sched/debug.c | 3 ++- kernel/sched/fair.c | 5 +++-- kernel/sched/pelt.h | 11 +---------- 4 files changed, 14 insertions(+), 13 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index d2c8813..28a98fc 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -350,11 +350,19 @@ struct load_weight { * Only for tasks we track a moving average of the past instantaneous * estimated utilization. This allows to absorb sporadic drops in utilization * of an otherwise almost periodic task. + * + * The UTIL_AVG_UNCHANGED flag is used to synchronize util_est with util_avg + * updates. When a task is dequeued, its util_est should not be updated if its + * util_avg has not been updated in the meantime. + * This information is mapped into the MSB bit of util_est.enqueued at dequeue + * time. Since max value of util_est.enqueued for a task is 1024 (PELT util_avg + * for a task) it is safe to use MSB. */ struct util_est { unsigned int enqueued; unsigned int ewma; #define UTIL_EST_WEIGHT_SHIFT 2 +#define UTIL_AVG_UNCHANGED 0x80000000 } __attribute__((__aligned__(sizeof(u64)))); /* diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 9c882f2..c5aacbd 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -885,6 +885,7 @@ static const struct seq_operations sched_debug_sops = { #define __PS(S, F) SEQ_printf(m, "%-45s:%21Ld\n", S, (long long)(F)) #define __P(F) __PS(#F, F) #define P(F) __PS(#F, p->F) +#define PM(F, M) __PS(#F, p->F & (M)) #define __PSN(S, F) SEQ_printf(m, "%-45s:%14Ld.%06ld\n", S, SPLIT_NS((long long)(F))) #define __PN(F) __PSN(#F, F) #define PN(F) __PSN(#F, p->F) @@ -1011,7 +1012,7 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns, P(se.avg.util_avg); P(se.avg.last_update_time); P(se.avg.util_est.ewma); - P(se.avg.util_est.enqueued); + PM(se.avg.util_est.enqueued, ~UTIL_AVG_UNCHANGED); #endif #ifdef CONFIG_UCLAMP_TASK __PS("uclamp.min", p->uclamp_req[UCLAMP_MIN].value); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7b98fb3..2c8a935 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3907,7 +3907,7 @@ static inline unsigned long _task_util_est(struct task_struct *p) { struct util_est ue = READ_ONCE(p->se.avg.util_est); - return (max(ue.ewma, ue.enqueued) | UTIL_AVG_UNCHANGED); + return max(ue.ewma, (ue.enqueued & ~UTIL_AVG_UNCHANGED)); } static inline unsigned long task_util_est(struct task_struct *p) @@ -4007,7 +4007,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq, * Reset EWMA on utilization increases, the moving average is used only * to smooth utilization decreases. */ - ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED); + ue.enqueued = task_util(p); if (sched_feat(UTIL_EST_FASTUP)) { if (ue.ewma < ue.enqueued) { ue.ewma = ue.enqueued; @@ -4056,6 +4056,7 @@ static inline void util_est_update(struct cfs_rq *cfs_rq, ue.ewma += last_ewma_diff; ue.ewma >>= UTIL_EST_WEIGHT_SHIFT; done: + ue.enqueued |= UTIL_AVG_UNCHANGED; WRITE_ONCE(p->se.avg.util_est, ue); trace_sched_util_est_se_tp(&p->se); diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h index 1462846..cfe94ff 100644 --- a/kernel/sched/pelt.h +++ b/kernel/sched/pelt.h @@ -42,15 +42,6 @@ static inline u32 get_pelt_divider(struct sched_avg *avg) return LOAD_AVG_MAX - 1024 + avg->period_contrib; } -/* - * When a task is dequeued, its estimated utilization should not be update if - * its util_avg has not been updated at least once. - * This flag is used to synchronize util_avg updates with util_est updates. - * We map this information into the LSB bit of the utilization saved at - * dequeue time (i.e. util_est.dequeued). - */ -#define UTIL_AVG_UNCHANGED 0x1 - static inline void cfs_se_util_change(struct sched_avg *avg) { unsigned int enqueued; @@ -58,7 +49,7 @@ static inline void cfs_se_util_change(struct sched_avg *avg) if (!sched_feat(UTIL_EST)) return; - /* Avoid store if the flag has been already set */ + /* Avoid store if the flag has been already reset */ enqueued = avg->util_est.enqueued; if (!(enqueued & UTIL_AVG_UNCHANGED)) return;