diff options
| author | Chris Redpath <chris.redpath@arm.com> | 2014-08-12 14:50:54 +0100 |
|---|---|---|
| committer | Jon Medhurst <tixy@linaro.org> | 2014-08-12 17:46:57 +0100 |
| commit | f83262408293795e5186e9d1bf66d525b24fdb12 (patch) | |
| tree | 2a4cb0856459aad5c54c29e78ae7decb8801a75e | |
| parent | 65abdc9b50378783981ed2f3453a0aae090404e4 (diff) | |
HMP: Do not fork-boost tasks coming from PIDs <= 2
System services are generally started by init, whilst kernel threads
are started by kthreadd. We do not want to give those tasks a head
start, as this costs power for very little benefit. We do however
wish to do that for tasks which the user launches.
Further, some tasks allocate per-cpu timers directly after launch
which can lead to those tasks being always scheduled on a big CPU
when there is no computational need to do so. Not promoting services
to big CPUs on launch will prevent that unless a service allocates
their per-cpu resources after a period of intense computation, which
is not a common pattern.
Signed-off-by: Chris Redpath <chris.redpath@arm.com>
Signed-off-by: Jon Medhurst <tixy@linaro.org>
| -rw-r--r-- | include/linux/sched.h | 8 | ||||
| -rw-r--r-- | kernel/sched/core.c | 6 | ||||
| -rw-r--r-- | kernel/sched/fair.c | 2 |
3 files changed, 12 insertions, 4 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 0e2a546cdade..b36dd2de437d 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -946,6 +946,14 @@ struct sched_avg { u32 usage_avg_sum; }; +#ifdef CONFIG_SCHED_HMP +/* + * We want to avoid boosting any processes forked from init (PID 1) + * and kthreadd (assumed to be PID 2). + */ +#define hmp_task_should_forkboost(task) ((task->parent && task->parent->pid > 2)) +#endif + #ifdef CONFIG_SCHEDSTATS struct sched_statistics { u64 wait_start; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5f242330ef85..65aaa1c78ca1 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1629,9 +1629,9 @@ static void __sched_fork(struct task_struct *p) #ifdef CONFIG_SCHED_HMP /* 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.hmp_last_up_migration = 0; + p->se.avg.hmp_last_down_migration = 0; + if (hmp_task_should_forkboost(p)) { p->se.avg.load_avg_ratio = 1023; p->se.avg.load_avg_contrib = (1023 * scale_load_down(p->se.load.weight)); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 161da1ab3995..74a5adfefeb7 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4358,7 +4358,7 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) #ifdef CONFIG_SCHED_HMP /* always put non-kernel forking tasks on a big domain */ - if (p->mm && (sd_flag & SD_BALANCE_FORK)) { + if (unlikely(sd_flag & SD_BALANCE_FORK) && hmp_task_should_forkboost(p)) { new_cpu = hmp_select_faster_cpu(p, prev_cpu); if (new_cpu != NR_CPUS) { hmp_next_up_delay(&p->se, new_cpu); |