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ANDROID: sched/core: Add a latency-sensitive flag to uclamp

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Add a 'latency_sensitive' flag to uclamp in order to express the need
for some tasks to find a CPU where they can wake-up quickly. This is not
expected to be used without cgroup support, so add solely a cgroup
interface for it.

As this flag represents a boolean attribute and not an amount of
resources to be shared, it is not clear what the delegation logic should
be. As such, it is kept simple: every new cgroup starts with
latency_sensitive set to false, regardless of the parent.

In essence, this is similar to SchedTune's prefer-idle flag which was
used in android-4.19 and prior.

Change-Id: I722d8ecabb428bb7b95a5b54bc70a87f182dde2a
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
This commit is contained in:
Quentin Perret
2019-07-30 13:54:00 +01:00
committed by kondors1995
parent 1abcbcbea7
commit b5fa516b3a
2 changed files with 29 additions and 0 deletions
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27
kernel/sched/core.c
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@@ -8398,6 +8398,27 @@ static int cpu_uclamp_max_show(struct seq_file *sf, void *v)
cpu_uclamp_print(sf, UCLAMP_MAX);
return 0;
}
static int cpu_uclamp_ls_write_u64(struct cgroup_subsys_state *css,
struct cftype *cftype, u64 ls)
{
struct task_group *tg;
if (ls > 1)
return -EINVAL;
tg = css_tg(css);
tg->latency_sensitive = (unsigned int) ls;
return 0;
}
static u64 cpu_uclamp_ls_read_u64(struct cgroup_subsys_state *css,
struct cftype *cft)
{
struct task_group *tg = css_tg(css);
return (u64) tg->latency_sensitive;
}
#endif /* CONFIG_UCLAMP_TASK_GROUP */
#ifdef CONFIG_FAIR_GROUP_SCHED
@@ -8743,6 +8764,12 @@ static struct cftype cpu_files[] = {
.seq_show = cpu_uclamp_max_show,
.write = cpu_uclamp_max_write,
},
{
.name = "uclamp.latency_sensitive",
.flags = CFTYPE_NOT_ON_ROOT,
.read_u64 = cpu_uclamp_ls_read_u64,
.write_u64 = cpu_uclamp_ls_write_u64,
},
#endif
{ } /* Terminate */
};

2
kernel/sched/sched.h
View File

@@ -414,6 +414,8 @@ struct task_group {
struct uclamp_se uclamp_req[UCLAMP_CNT];
/* Effective clamp values used for a task group */
struct uclamp_se uclamp[UCLAMP_CNT];
/* Latency-sensitive flag used for a task group */
unsigned int latency_sensitive;
#endif
};