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authorChris Redpath <chris.redpath@arm.com>2013-06-17 16:08:40 +0100
committerJon Medhurst <tixy@linaro.org>2013-07-17 11:32:30 +0100
commit954978dd2cff81cc15745b9e581a1709e238f8ef (patch)
tree5b297723fc2cce8e5293b1b559bbe2952d2654ac
parent3f3b210703f80fe60dbfa13c25b30d4effbf9f4b (diff)
HMP: Force new non-kernel tasks onto big CPUs until load stabilises
Initialise the load stats for new tasks so that they do not see the instability in early task life which makes it so hard to decide which CPU is appropriate. Also, change the fork balance algorithm so that the least loaded of the CPUs in the big cluster is chosen regardless of the bigness of the parent task. This is intended to help performance for applications which use many short-lived tasks. Although best practise is usually to use a thread pool, apps which do not do this should not be subject to the randomness of the early stats. We should ignore real-time threads for forking on big CPUs, but it is not possible to figure out if a new thread is real-time or not at the fork stage. Instead, we prevent kernel threads from getting the initial boost - when they later become real-time they will only be on big if their compute requirements demand it. Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Chris Redpath <chris.redpath@arm.com>
-rw-r--r--kernel/sched/core.c14
-rw-r--r--kernel/sched/fair.c22
2 files changed, 34 insertions, 2 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e45295dc33a..4c53da3781e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1618,8 +1618,18 @@ static void __sched_fork(struct task_struct *p)
p->se.avg.runnable_avg_period = 0;
p->se.avg.runnable_avg_sum = 0;
#ifdef CONFIG_SCHED_HMP
- p->se.avg.hmp_last_up_migration = 0;
- p->se.avg.hmp_last_down_migration = 0;
+ /* keep LOAD_AVG_MAX in sync with fair.c if load avg series is changed */
+#define LOAD_AVG_MAX 47742
+ if (p->mm) {
+ p->se.avg.hmp_last_up_migration = 0;
+ p->se.avg.hmp_last_down_migration = 0;
+ p->se.avg.load_avg_ratio = 1023;
+ p->se.avg.load_avg_contrib =
+ (1023 * scale_load_down(p->se.load.weight));
+ p->se.avg.runnable_avg_period = LOAD_AVG_MAX;
+ p->se.avg.runnable_avg_sum = LOAD_AVG_MAX;
+ p->se.avg.usage_avg_sum = LOAD_AVG_MAX;
+ }
#endif
#endif
#ifdef CONFIG_SCHEDSTATS
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a38a3edb07d..1b784eea661 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3957,6 +3957,28 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
if (p->nr_cpus_allowed == 1)
return prev_cpu;
+#ifdef CONFIG_SCHED_HMP
+ /* always put non-kernel forking tasks on a big domain */
+ if (p->mm && (sd_flag & SD_BALANCE_FORK)) {
+ if(hmp_cpu_is_fastest(prev_cpu)) {
+ struct hmp_domain *hmpdom = list_entry(&hmp_cpu_domain(prev_cpu)->hmp_domains, struct hmp_domain, hmp_domains);
+ __always_unused int lowest_ratio = hmp_domain_min_load(hmpdom, &new_cpu);
+ if(new_cpu != NR_CPUS && cpumask_test_cpu(new_cpu,tsk_cpus_allowed(p)))
+ return new_cpu;
+ else {
+ new_cpu = cpumask_any_and(&hmp_faster_domain(cpu)->cpus,
+ tsk_cpus_allowed(p));
+ if(new_cpu < nr_cpu_ids)
+ return new_cpu;
+ }
+ } else {
+ new_cpu = hmp_select_faster_cpu(p, prev_cpu);
+ if (new_cpu != NR_CPUS)
+ return new_cpu;
+ }
+ }
+#endif
+
if (sd_flag & SD_BALANCE_WAKE) {
if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
want_affine = 1;