lkml.org 
[lkml]   [2016]   [Jul]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v3 08/13] sched: Store maximum per-cpu capacity in root domain
Date
From: Dietmar Eggemann <dietmar.eggemann@arm.com>

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).

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
---
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..600f1296aa4c 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(rq->rd->max_cpu_capacity))
+ WRITE_ONCE(rq->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
\
 
 \ /
  Last update: 2016-07-25 16:21    [W:0.148 / U:0.776 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site