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Commit c28f9d39 authored by Quentin Perret's avatar Quentin Perret Committed by Quentin Perret
Browse files

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



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: default avatarQuentin Perret <quentin.perret@arm.com>
parent 588085fe

kernel/sched/core.c

+33 −0
Original line number Diff line number Diff line
@@ -7356,6 +7356,27 @@ 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
@@ -7716,6 +7737,12 @@ static struct cftype cpu_legacy_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 */

};
@@ -7897,6 +7924,12 @@ 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 */

};

kernel/sched/sched.h

+2 −0
Original line number Diff line number Diff line
@@ -399,6 +399,8 @@ 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



};