From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753360AbcHPMYZ (ORCPT ); Tue, 16 Aug 2016 08:24:25 -0400 Received: from mail-wm0-f52.google.com ([74.125.82.52]:36168 "EHLO mail-wm0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751516AbcHPMYY (ORCPT ); Tue, 16 Aug 2016 08:24:24 -0400 MIME-Version: 1.0 In-Reply-To: <26c69258-9947-f830-a53e-0c54e7750646@arm.com> References: <1469453670-2660-1-git-send-email-morten.rasmussen@arm.com> <1469453670-2660-9-git-send-email-morten.rasmussen@arm.com> <26c69258-9947-f830-a53e-0c54e7750646@arm.com> From: Vincent Guittot Date: Tue, 16 Aug 2016 14:24:02 +0200 Message-ID: Subject: Re: [PATCH v3 08/13] sched: Store maximum per-cpu capacity in root domain To: Dietmar Eggemann Cc: Morten Rasmussen , Peter Zijlstra , "mingo@redhat.com" , Yuyang Du , mgalbraith@suse.de, Sai Charan Gurrappadi , freedom.tan@mediatek.com, keita.kobayashi.ym@renesas.com, linux-kernel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1 August 2016 at 20:53, Dietmar Eggemann wrote: > On 25/07/16 14:34, Morten Rasmussen wrote: > > [...] > >> @@ -6923,11 +6924,22 @@ static int build_sched_domains(const struct cpumask *cpu_map, >> /* Attach the domains */ >> rcu_read_lock(); >> for_each_cpu(i, cpu_map) { >> + rq = cpu_rq(i); >> sd = *per_cpu_ptr(d.sd, i); >> + >> + /* Use READ_ONCE/WRITE_ONCE to avoid load/store tearing */ >> + if (rq->cpu_capacity_orig > READ_ONCE(rq->rd->max_cpu_capacity)) >> + WRITE_ONCE(rq->rd->max_cpu_capacity, rq->cpu_capacity_orig); > > We have to use d.rd rather rq->rd here since from v3 on we have this if > condition in front of the cpu_attach_domain() call which replaces > rq->rd with d.rd. Fixed patch below. > >> + >> cpu_attach_domain(sd, d.rd, i); >> } >> rcu_read_unlock(); >> >> + if (rq) { >> + pr_info("span: %*pbl (max cpu_capacity = %lu)\n", >> + cpumask_pr_args(cpu_map), rq->rd->max_cpu_capacity); >> + } >> + >> ret = 0; >> error: >> __free_domain_allocs(&d, alloc_state, cpu_map); > > [...] > > -- >8 -- > > From: Dietmar Eggemann > > To be able to compare the capacity of the target cpu with the highest > available cpu capacity, store the maximum per-cpu capacity in the root > domain. > > The max per-cpu capacity should be 1024 for all systems except SMT, > where the capacity is currently based on smt_gain and the number of > hardware threads and is <1024. If SMT can be brought to work with a > per-thread capacity of 1024, this patch can be dropped and replaced by a > hard-coded max capacity of 1024 (=SCHED_CAPACITY_SCALE). FWIW, Acked-by: Vincent Guittot > > cc: Ingo Molnar > cc: Peter Zijlstra > > Signed-off-by: Dietmar Eggemann > Signed-off-by: Morten Rasmussen > --- > kernel/sched/core.c | 12 ++++++++++++ > kernel/sched/sched.h | 2 ++ > 2 files changed, 14 insertions(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index a0a74b2d9f41..db03e6226d54 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -6873,6 +6873,7 @@ static int build_sched_domains(const struct cpumask *cpu_map, > enum s_alloc alloc_state; > struct sched_domain *sd; > struct s_data d; > + struct rq *rq = NULL; > int i, ret = -ENOMEM; > > alloc_state = __visit_domain_allocation_hell(&d, cpu_map); > @@ -6923,11 +6924,22 @@ static int build_sched_domains(const struct cpumask *cpu_map, > /* Attach the domains */ > rcu_read_lock(); > for_each_cpu(i, cpu_map) { > + rq = cpu_rq(i); > sd = *per_cpu_ptr(d.sd, i); > + > + /* Use READ_ONCE/WRITE_ONCE to avoid load/store tearing */ > + if (rq->cpu_capacity_orig > READ_ONCE(d.rd->max_cpu_capacity)) > + WRITE_ONCE(d.rd->max_cpu_capacity, rq->cpu_capacity_orig); > + > cpu_attach_domain(sd, d.rd, i); > } > rcu_read_unlock(); > > + if (rq) { > + pr_info("span: %*pbl (max cpu_capacity = %lu)\n", > + cpumask_pr_args(cpu_map), rq->rd->max_cpu_capacity); > + } > + > ret = 0; > error: > __free_domain_allocs(&d, alloc_state, cpu_map); > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index f44da95c70cd..444d8f38743f 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -565,6 +565,8 @@ struct root_domain { > */ > cpumask_var_t rto_mask; > struct cpupri cpupri; > + > + unsigned long max_cpu_capacity; > }; > > extern struct root_domain def_root_domain; > -- > 1.9.1