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sched/fair: add tunable to set initial task load

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The choice of initial task load upon fork has a large influence
on CPU and OPP selection when scheduler-driven DVFS is in use.
Make this tuneable by adding a new sysctl "sched_initial_task_util".

If the sched governor is not used, the default remains at SCHED_LOAD_SCALE
Otherwise, the value from the sysctl is used. This defaults to 0.

Signed-off-by: "Todd Kjos <tkjos@google.com>"
This commit is contained in:
Todd Kjos 2016-03-11 16:44:16 -08:00 • committed by John Stultz
parent 4a5e890ec6
commit c50cc2299c
3 changed files with 12 additions and 1 deletions
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1
include/linux/sched/sysctl.h
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@ -41,6 +41,7 @@ extern unsigned int sysctl_sched_wakeup_granularity;
extern unsigned int sysctl_sched_child_runs_first;
extern unsigned int sysctl_sched_is_big_little;
extern unsigned int sysctl_sched_sync_hint_enable;
extern unsigned int sysctl_sched_initial_task_util;
extern unsigned int sysctl_sched_cstate_aware;
enum sched_tunable_scaling {

5
kernel/sched/fair.c
View file

@ -53,6 +53,7 @@ unsigned int normalized_sysctl_sched_latency = 6000000ULL;
unsigned int sysctl_sched_is_big_little = 0;
unsigned int sysctl_sched_sync_hint_enable = 1;
unsigned int sysctl_sched_initial_task_util = 0;
unsigned int sysctl_sched_cstate_aware = 1;
/*
@ -687,7 +688,9 @@ void init_entity_runnable_average(struct sched_entity *se)
sa->period_contrib = 1023;
sa->load_avg = scale_load_down(se->load.weight);
sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
sa->util_avg = sched_freq() ?
sysctl_sched_initial_task_util :
scale_load_down(SCHED_LOAD_SCALE);
sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
}

7
kernel/sysctl.c
View file

@ -317,6 +317,13 @@ static struct ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "sched_initial_task_util",
.data = &sysctl_sched_initial_task_util,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "sched_cstate_aware",
.data = &sysctl_sched_cstate_aware,