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 9FD9BC433ED for ; Fri, 9 Apr 2021 16:14:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 707CF61041 for ; Fri, 9 Apr 2021 16:14:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233786AbhDIQPA (ORCPT ); Fri, 9 Apr 2021 12:15:00 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:51576 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229665AbhDIQOq (ORCPT ); Fri, 9 Apr 2021 12:14:46 -0400 Date: Fri, 09 Apr 2021 16:14:30 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1617984872; 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=/vaVZHOURXnaFpdHiHpXBNeYCgIFf8IrI3j+izmDIIQ=; b=RoSu0n/ePeKnoAFLQ+FDb/2er+XQAqIeeh2Oh4oEEq5OjJTkVF08o+JGksbaDt+KOQadZY /09Ia1CL9gzXXC4ulVVllWDS6vrX0eTJooxXF4ynrj3aQed/KWLwozPAeCdytUXOQ59Aow N3N6Iduy3qQMuTk+V5EgCzJDGGhVEqEZV/ek8CJCf1ckIdZCitcZ7+fp06jDrRSj/GlPdL y/Tb/hBrsU8ggEX+OgYzzssGRrkReceV5foXHBR2Mg0y6diKn5kSrqsZqyjH1n+sVXZGpa XC1K4kxaa2vhHixF4eNFKTKBdVWCLGDzpJ51IGWU9FW/+R3SQewlyJuKQjnmAw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1617984872; 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=/vaVZHOURXnaFpdHiHpXBNeYCgIFf8IrI3j+izmDIIQ=; b=qKnXVGeXmYJntCNIfs9LRi3jgk0eQO+PN6JNu1M6P93TJ0YiKubNHb7aj6J8nVxUOC5AYj k2WlC67Qt/fstKDw== From: "tip-bot2 for Valentin Schneider" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/fair: Introduce a CPU capacity comparison helper Cc: Valentin Schneider , "Peter Zijlstra (Intel)" , Dietmar Eggemann , Qais Yousef , Vincent Guittot , Lingutla Chandrasekhar , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210407220628.3798191-4-valentin.schneider@arm.com> References: <20210407220628.3798191-4-valentin.schneider@arm.com> MIME-Version: 1.0 Message-ID: <161798487099.29796.13541527645202079257.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/core branch of tip: Commit-ID: 4aed8aa41524a1fc6439171881c2bb7ace197528 Gitweb: https://git.kernel.org/tip/4aed8aa41524a1fc6439171881c2bb7ace197528 Author: Valentin Schneider AuthorDate: Wed, 07 Apr 2021 23:06:28 +01:00 Committer: Peter Zijlstra CommitterDate: Fri, 09 Apr 2021 18:02:21 +02:00 sched/fair: Introduce a CPU capacity comparison helper During load-balance, groups classified as group_misfit_task are filtered out if they do not pass group_smaller_max_cpu_capacity(, ); which itself employs fits_capacity() to compare the sgc->max_capacity of both groups. Due to the underlying margin, fits_capacity(X, 1024) will return false for any X > 819. Tough luck, the capacity_orig's on e.g. the Pixel 4 are {261, 871, 1024}. If a CPU-bound task ends up on one of those "medium" CPUs, misfit migration will never intentionally upmigrate it to a CPU of higher capacity due to the aforementioned margin. One may argue the 20% margin of fits_capacity() is excessive in the advent of counter-enhanced load tracking (APERF/MPERF, AMUs), but one point here is that fits_capacity() is meant to compare a utilization value to a capacity value, whereas here it is being used to compare two capacity values. As CPU capacity and task utilization have different dynamics, a sensible approach here would be to add a new helper dedicated to comparing CPU capacities. Also note that comparing capacity extrema of local and source sched_group's doesn't make much sense when at the day of the day the imbalance will be pulled by a known env->dst_cpu, whose capacity can be anywhere within the local group's capacity extrema. While at it, replace group_smaller_{min, max}_cpu_capacity() with comparisons of the source group's min/max capacity and the destination CPU's capacity. Signed-off-by: Valentin Schneider Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Reviewed-by: Qais Yousef Reviewed-by: Vincent Guittot Tested-by: Lingutla Chandrasekhar Link: https://lkml.kernel.org/r/20210407220628.3798191-4-valentin.schneider@arm.com --- kernel/sched/fair.c | 33 ++++++++++----------------------- 1 file changed, 10 insertions(+), 23 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 356637a..9b8ae02 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -113,6 +113,13 @@ int __weak arch_asym_cpu_priority(int cpu) */ #define fits_capacity(cap, max) ((cap) * 1280 < (max) * 1024) +/* + * The margin used when comparing CPU capacities. + * is 'cap1' noticeably greater than 'cap2' + * + * (default: ~5%) + */ +#define capacity_greater(cap1, cap2) ((cap1) * 1024 > (cap2) * 1078) #endif #ifdef CONFIG_CFS_BANDWIDTH @@ -8395,26 +8402,6 @@ group_is_overloaded(unsigned int imbalance_pct, struct sg_lb_stats *sgs) return false; } -/* - * group_smaller_min_cpu_capacity: Returns true if sched_group sg has smaller - * per-CPU capacity than sched_group ref. - */ -static inline bool -group_smaller_min_cpu_capacity(struct sched_group *sg, struct sched_group *ref) -{ - return fits_capacity(sg->sgc->min_capacity, ref->sgc->min_capacity); -} - -/* - * group_smaller_max_cpu_capacity: Returns true if sched_group sg has smaller - * per-CPU capacity_orig than sched_group ref. - */ -static inline bool -group_smaller_max_cpu_capacity(struct sched_group *sg, struct sched_group *ref) -{ - return fits_capacity(sg->sgc->max_capacity, ref->sgc->max_capacity); -} - static inline enum group_type group_classify(unsigned int imbalance_pct, struct sched_group *group, @@ -8570,7 +8557,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, * internally or be covered by avg_load imbalance (eventually). */ if (sgs->group_type == group_misfit_task && - (!group_smaller_max_cpu_capacity(sg, sds->local) || + (!capacity_greater(capacity_of(env->dst_cpu), sg->sgc->max_capacity) || sds->local_stat.group_type != group_has_spare)) return false; @@ -8654,7 +8641,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, */ if ((env->sd->flags & SD_ASYM_CPUCAPACITY) && (sgs->group_type <= group_fully_busy) && - (group_smaller_min_cpu_capacity(sds->local, sg))) + (capacity_greater(sg->sgc->min_capacity, capacity_of(env->dst_cpu)))) return false; return true; @@ -9454,7 +9441,7 @@ static struct rq *find_busiest_queue(struct lb_env *env, * average load. */ if (env->sd->flags & SD_ASYM_CPUCAPACITY && - capacity_of(env->dst_cpu) < capacity && + !capacity_greater(capacity_of(env->dst_cpu), capacity) && nr_running == 1) continue;