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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 D1BF7ECDFB8 for ; Fri, 20 Jul 2018 13:33:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8D16D2084A for ; Fri, 20 Jul 2018 13:33:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8D16D2084A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732707AbeGTOWE (ORCPT ); Fri, 20 Jul 2018 10:22:04 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:36252 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728252AbeGTOWD (ORCPT ); Fri, 20 Jul 2018 10:22:03 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BE00015A2; Fri, 20 Jul 2018 06:33:44 -0700 (PDT) Received: from e105550-lin.cambridge.arm.com (e105550-lin.cambridge.arm.com [10.1.211.30]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 23E333F7C7; Fri, 20 Jul 2018 06:33:43 -0700 (PDT) From: Morten Rasmussen To: peterz@infradead.org, mingo@redhat.com Cc: valentin.schneider@arm.com, dietmar.eggemann@arm.com, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Morten Rasmussen Subject: [PATCH 1/4] sched/topology: SD_ASYM_CPUCAPACITY flag detection Date: Fri, 20 Jul 2018 14:32:31 +0100 Message-Id: <1532093554-30504-2-git-send-email-morten.rasmussen@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1532093554-30504-1-git-send-email-morten.rasmussen@arm.com> References: <1532093554-30504-1-git-send-email-morten.rasmussen@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The SD_ASYM_CPUCAPACITY sched_domain flag is supposed to mark the sched_domain in the hierarchy where all cpu capacities are visible for any cpu's point of view on asymmetric cpu capacity systems. The scheduler can then take to take capacity asymmetry into account when balancing at this level. It also serves as an indicator for how wide task placement heuristics have to search to consider all available cpu capacities as asymmetric systems might often appear symmetric at smallest level(s) of the sched_domain hierarchy. The flag has been around for while but so far only been set by out-of-tree code in Android kernels. One solution is to let each architecture provide the flag through a custom sched_domain topology array and associated mask and flag functions. However, SD_ASYM_CPUCAPACITY is special in the sense that it depends on the capacity and presence of all cpus in the system, i.e. when hotplugging all cpus out except those with one particular cpu capacity the flag should disappear even if the sched_domains don't collapse. Similarly, the flag is affected by cpusets where load-balancing is turned off. Detecting when the flags should be set therefore depends not only on topology information but also the cpuset configuration and hotplug state. The arch code doesn't have easy access to the cpuset configuration. Instead, this patch implements the flag detection in generic code where cpusets and hotplug state is already taken care of. All the arch is responsible for is to implement arch_scale_cpu_capacity() and force a full rebuild of the sched_domain hierarchy if capacities are updated, e.g. later in the boot process when cpufreq has initialized. cc: Ingo Molnar cc: Peter Zijlstra Signed-off-by: Morten Rasmussen --- include/linux/sched/topology.h | 2 +- kernel/sched/topology.c | 81 ++++++++++++++++++++++++++++++++++++++---- 2 files changed, 76 insertions(+), 7 deletions(-) diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h index 26347741ba50..4fe2e49ab13b 100644 --- a/include/linux/sched/topology.h +++ b/include/linux/sched/topology.h @@ -23,7 +23,7 @@ #define SD_BALANCE_FORK 0x0008 /* Balance on fork, clone */ #define SD_BALANCE_WAKE 0x0010 /* Balance on wakeup */ #define SD_WAKE_AFFINE 0x0020 /* Wake task to waking CPU */ -#define SD_ASYM_CPUCAPACITY 0x0040 /* Groups have different max cpu capacities */ +#define SD_ASYM_CPUCAPACITY 0x0040 /* Domain members have different cpu capacities */ #define SD_SHARE_CPUCAPACITY 0x0080 /* Domain members share cpu capacity */ #define SD_SHARE_POWERDOMAIN 0x0100 /* Domain members share power domain */ #define SD_SHARE_PKG_RESOURCES 0x0200 /* Domain members share cpu pkg resources */ diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 05a831427bc7..b8f41d557612 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -1061,7 +1061,6 @@ static struct cpumask ***sched_domains_numa_masks; * SD_SHARE_PKG_RESOURCES - describes shared caches * SD_NUMA - describes NUMA topologies * SD_SHARE_POWERDOMAIN - describes shared power domain - * SD_ASYM_CPUCAPACITY - describes mixed capacity topologies * * Odd one out, which beside describing the topology has a quirk also * prescribes the desired behaviour that goes along with it: @@ -1073,13 +1072,12 @@ static struct cpumask ***sched_domains_numa_masks; SD_SHARE_PKG_RESOURCES | \ SD_NUMA | \ SD_ASYM_PACKING | \ - SD_ASYM_CPUCAPACITY | \ SD_SHARE_POWERDOMAIN) static struct sched_domain * sd_init(struct sched_domain_topology_level *tl, const struct cpumask *cpu_map, - struct sched_domain *child, int cpu) + struct sched_domain *child, int dflags, int cpu) { struct sd_data *sdd = &tl->data; struct sched_domain *sd = *per_cpu_ptr(sdd->sd, cpu); @@ -1100,6 +1098,9 @@ sd_init(struct sched_domain_topology_level *tl, "wrong sd_flags in topology description\n")) sd_flags &= ~TOPOLOGY_SD_FLAGS; + /* Apply detected topology flags */ + sd_flags |= dflags; + *sd = (struct sched_domain){ .min_interval = sd_weight, .max_interval = 2*sd_weight, @@ -1607,9 +1608,9 @@ static void __sdt_free(const struct cpumask *cpu_map) static struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl, const struct cpumask *cpu_map, struct sched_domain_attr *attr, - struct sched_domain *child, int cpu) + struct sched_domain *child, int dflags, int cpu) { - struct sched_domain *sd = sd_init(tl, cpu_map, child, cpu); + struct sched_domain *sd = sd_init(tl, cpu_map, child, dflags, cpu); if (child) { sd->level = child->level + 1; @@ -1636,6 +1637,65 @@ static struct sched_domain *build_sched_domain(struct sched_domain_topology_leve } /* + * Find the sched_domain_topology_level where all cpu capacities are visible + * for all cpus. + */ +static struct sched_domain_topology_level +*asym_cpu_capacity_level(const struct cpumask *cpu_map) +{ + int i, j, asym_level = 0; + bool asym = false; + struct sched_domain_topology_level *tl, *asym_tl = NULL; + unsigned long cap; + + /* Is there any asymmetry? */ + cap = arch_scale_cpu_capacity(NULL, cpumask_first(cpu_map)); + + for_each_cpu(i, cpu_map) { + if (arch_scale_cpu_capacity(NULL, i) != cap) { + asym = true; + break; + } + } + + if (!asym) + return NULL; + + /* + * Examine topology from all cpu's point of views to detect the lowest + * sched_domain_topology_level where a highest capacity cpu is visible + * to everyone. + */ + for_each_cpu(i, cpu_map) { + unsigned long max_capacity = arch_scale_cpu_capacity(NULL, i); + int tl_id = 0; + + for_each_sd_topology(tl) { + if (tl_id < asym_level) + goto next_level; + + for_each_cpu_and(j, tl->mask(i), cpu_map) { + unsigned long capacity; + + capacity = arch_scale_cpu_capacity(NULL, j); + + if (capacity <= max_capacity) + continue; + + max_capacity = capacity; + asym_level = tl_id; + asym_tl = tl; + } +next_level: + tl_id++; + } + } + + return asym_tl; +} + + +/* * Build sched domains for a given set of CPUs and attach the sched domains * to the individual CPUs */ @@ -1647,18 +1707,27 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att struct s_data d; struct rq *rq = NULL; int i, ret = -ENOMEM; + struct sched_domain_topology_level *tl_asym; alloc_state = __visit_domain_allocation_hell(&d, cpu_map); if (alloc_state != sa_rootdomain) goto error; + tl_asym = asym_cpu_capacity_level(cpu_map); + /* Set up domains for CPUs specified by the cpu_map: */ for_each_cpu(i, cpu_map) { struct sched_domain_topology_level *tl; sd = NULL; for_each_sd_topology(tl) { - sd = build_sched_domain(tl, cpu_map, attr, sd, i); + int dflags = 0; + + if (tl == tl_asym) + dflags |= SD_ASYM_CPUCAPACITY; + + sd = build_sched_domain(tl, cpu_map, attr, sd, dflags, i); + if (tl == sched_domain_topology) *per_cpu_ptr(d.sd, i) = sd; if (tl->flags & SDTL_OVERLAP) -- 2.7.4