From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2997365AbdD1Nc6 (ORCPT ); Fri, 28 Apr 2017 09:32:58 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:60486 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1162706AbdD1Nce (ORCPT ); Fri, 28 Apr 2017 09:32:34 -0400 Message-Id: <20170428132502.451602973@infradead.org> User-Agent: quilt/0.63-1 Date: Fri, 28 Apr 2017 15:20:00 +0200 From: Peter Zijlstra To: mingo@kernel.org, lvenanci@redhat.com Cc: lwang@redhat.com, riel@redhat.com, efault@gmx.de, tglx@linutronix.de, linux-kernel@vger.kernel.org, peterz@infradead.org Subject: [PATCH 02/14] sched,cpumask: Export for_each_cpu_wrap() References: <20170428131958.893188882@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=peter_zijlstra-sched_topology-fix_sched_groups_on_numa_machines_with_mesh_topology.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org More users for for_each_cpu_wrap() have appeared. Promote the construct to generic cpumask interface. The implementation is slightly modified to reduce arguments. Cc: Ingo Molnar Cc: Mike Galbraith Cc: Lauro Ramos Venancio Cc: Thomas Gleixner Cc: Rik van Riel Signed-off-by: Peter Zijlstra (Intel) Link: http://lkml.kernel.org/r/20170414122005.o35me2h5nowqkxbv@hirez.programming.kicks-ass.net --- include/linux/cpumask.h | 17 +++++++++++++++++ kernel/sched/fair.c | 45 ++++----------------------------------------- lib/cpumask.c | 32 ++++++++++++++++++++++++++++++++ 3 files changed, 53 insertions(+), 41 deletions(-) --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -236,6 +236,23 @@ unsigned int cpumask_local_spread(unsign (cpu) = cpumask_next_zero((cpu), (mask)), \ (cpu) < nr_cpu_ids;) +extern int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap); + +/** + * for_each_cpu_wrap - iterate over every cpu in a mask, starting at a specified location + * @cpu: the (optionally unsigned) integer iterator + * @mask: the cpumask poiter + * @start: the start location + * + * The implementation does not assume any bit in @mask is set (including @start). + * + * After the loop, cpu is >= nr_cpu_ids. + */ +#define for_each_cpu_wrap(cpu, mask, start) \ + for ((cpu) = cpumask_next_wrap((start)-1, (mask), (start), false); \ + (cpu) < nr_cpumask_bits; \ + (cpu) = cpumask_next_wrap((cpu), (mask), (start), true)) + /** * for_each_cpu_and - iterate over every cpu in both masks * @cpu: the (optionally unsigned) integer iterator --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5691,43 +5691,6 @@ find_idlest_cpu(struct sched_group *grou return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu; } -/* - * Implement a for_each_cpu() variant that starts the scan at a given cpu - * (@start), and wraps around. - * - * This is used to scan for idle CPUs; such that not all CPUs looking for an - * idle CPU find the same CPU. The down-side is that tasks tend to cycle - * through the LLC domain. - * - * Especially tbench is found sensitive to this. - */ - -static int cpumask_next_wrap(int n, const struct cpumask *mask, int start, int *wrapped) -{ - int next; - -again: - next = find_next_bit(cpumask_bits(mask), nr_cpumask_bits, n+1); - - if (*wrapped) { - if (next >= start) - return nr_cpumask_bits; - } else { - if (next >= nr_cpumask_bits) { - *wrapped = 1; - n = -1; - goto again; - } - } - - return next; -} - -#define for_each_cpu_wrap(cpu, mask, start, wrap) \ - for ((wrap) = 0, (cpu) = (start)-1; \ - (cpu) = cpumask_next_wrap((cpu), (mask), (start), &(wrap)), \ - (cpu) < nr_cpumask_bits; ) - #ifdef CONFIG_SCHED_SMT static inline void set_idle_cores(int cpu, int val) @@ -5787,7 +5750,7 @@ void __update_idle_core(struct rq *rq) static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target) { struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); - int core, cpu, wrap; + int core, cpu; if (!static_branch_likely(&sched_smt_present)) return -1; @@ -5797,7 +5760,7 @@ static int select_idle_core(struct task_ cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed); - for_each_cpu_wrap(core, cpus, target, wrap) { + for_each_cpu_wrap(core, cpus, target) { bool idle = true; for_each_cpu(cpu, cpu_smt_mask(core)) { @@ -5863,7 +5826,7 @@ static int select_idle_cpu(struct task_s u64 avg_cost, avg_idle = this_rq()->avg_idle; u64 time, cost; s64 delta; - int cpu, wrap; + int cpu; this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); if (!this_sd) @@ -5880,7 +5843,7 @@ static int select_idle_cpu(struct task_s time = local_clock(); - for_each_cpu_wrap(cpu, sched_domain_span(sd), target, wrap) { + for_each_cpu_wrap(cpu, sched_domain_span(sd), target) { if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) continue; if (idle_cpu(cpu)) --- a/lib/cpumask.c +++ b/lib/cpumask.c @@ -43,6 +43,38 @@ int cpumask_any_but(const struct cpumask } EXPORT_SYMBOL(cpumask_any_but); +/** + * cpumask_next_wrap - helper to implement for_each_cpu_wrap + * @n: the cpu prior to the place to search + * @mask: the cpumask pointer + * @start: the start point of the iteration + * @wrap: assume @n crossing @start terminates the iteration + * + * Returns >= nr_cpu_ids on completion + * + * Note: the @wrap argument is required for the start condition when + * we cannot assume @start is set in @mask. + */ +int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap) +{ + int next; + +again: + next = cpumask_next(n, mask); + + if (wrap && n < start && next >= start) { + return nr_cpumask_bits; + + } else if (next >= nr_cpumask_bits) { + wrap = true; + n = -1; + goto again; + } + + return next; +} +EXPORT_SYMBOL(cpumask_next_wrap); + /* These are not inline because of header tangles. */ #ifdef CONFIG_CPUMASK_OFFSTACK /**