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Commit 7e767d3e authored by Srivatsa Vaddagiri's avatar Srivatsa Vaddagiri
Browse files

sched: Add userspace interface to set PF_WAKE_UP_IDLE 



sched_prefer_idle flag controls whether tasks can be woken to any
available idle cpu. It may be desirable to set sched_prefer_idle to 0
so that most tasks wake up to non-idle cpus under mostly_idle
threshold and have specialized tasks override this behavior through
other means. PF_WAKE_UP_IDLE flag per task provides exactly that. It
lets tasks with PF_WAKE_UP_IDLE flag set be woken up to any available
idle cpu independent of sched_prefer_idle flag setting. Currently
only kernel-space API exists to set PF_WAKE_UP_IDLE flag for a task.
This patch adds a user-space API (in /proc filesystem) to set
PF_WAKE_UP_IDLE flag for a given task. /proc/[pid]/sched_wake_up_idle
file can be written to set or clear PF_WAKE_UP_IDLE flag for a given
task.

Change-Id: I13a37e740195e503f457ebe291d54e83b230fbeb
Signed-off-by: default avatarSrivatsa Vaddagiri <vatsa@codeaurora.org>
parent d6415d1a

Documentation/scheduler/sched-hmp.txt

+10 −1
Original line number Diff line number Diff line
@@ -825,7 +825,16 @@ power-efficient cpu found while scanning cluster's online cpus. 
- PF_WAKE_UP_IDLE

	Any task that has this flag set in its 'task_struct.flags' field will be

always woken to idle cpu. Further any task woken by such tasks will be also

placed on idle cpu.

placed on idle cpu. PF_WAKE_UP_IDLE flag is inherited by children of a task.

It can be modified for a task in two ways:



	> kernel-space interface

		set_wake_up_idle() needs to be called in the context of a task

		to set or clear its PF_WAKE_UP_IDLE flag.



	> user-space interface

		/proc/[pid]/sched_wake_up_idle file needs to be written to for

		setting or clearing PF_WAKE_UP_IDLE flag for a given task



For some low band of frequency, spread of task on all available cpus can be

groslly power-inefficient. As an example, consider two tasks that each need

fs/proc/base.c

+72 −2
Original line number Diff line number Diff line
@@ -1345,11 +1345,78 @@ static const struct file_operations proc_pid_sched_operations = { 


#endif



#ifdef CONFIG_SCHED_HMP



/*

 * Print out various scheduling related per-task fields:

 */



#ifdef CONFIG_SMP



static int sched_wake_up_idle_show(struct seq_file *m, void *v)

{

	struct inode *inode = m->private;

	struct task_struct *p;



	p = get_proc_task(inode);

	if (!p)

		return -ESRCH;



	seq_printf(m, "%d\n", sched_get_wake_up_idle(p));



	put_task_struct(p);



	return 0;

}



static ssize_t

sched_wake_up_idle_write(struct file *file, const char __user *buf,

	    size_t count, loff_t *offset)

{

	struct inode *inode = file_inode(file);

	struct task_struct *p;

	char buffer[PROC_NUMBUF];

	int wake_up_idle, err;



	memset(buffer, 0, sizeof(buffer));

	if (count > sizeof(buffer) - 1)

		count = sizeof(buffer) - 1;

	if (copy_from_user(buffer, buf, count)) {

		err = -EFAULT;

		goto out;

	}



	err = kstrtoint(strstrip(buffer), 0, &wake_up_idle);

	if (err)

		goto out;



	p = get_proc_task(inode);

	if (!p)

		return -ESRCH;



	err = sched_set_wake_up_idle(p, wake_up_idle);



	put_task_struct(p);



out:

	return err < 0 ? err : count;

}



static int sched_wake_up_idle_open(struct inode *inode, struct file *filp)

{

	return single_open(filp, sched_wake_up_idle_show, inode);

}



static const struct file_operations proc_pid_sched_wake_up_idle_operations = {

	.open		= sched_wake_up_idle_open,

	.read		= seq_read,

	.write		= sched_wake_up_idle_write,

	.llseek		= seq_lseek,

	.release	= single_release,

};



#endif	/* CONFIG_SMP */



#ifdef CONFIG_SCHED_HMP



static int sched_init_task_load_show(struct seq_file *m, void *v)

{

	struct inode *inode = m->private;
@@ -2763,6 +2830,9 @@ static const struct pid_entry tgid_base_stuff[] = { 
	ONE("status",     S_IRUGO, proc_pid_status),

	ONE("personality", S_IRUGO, proc_pid_personality),

	INF("limits",	  S_IRUGO, proc_pid_limits),

#ifdef CONFIG_SMP

	REG("sched_wake_up_idle",      S_IRUGO|S_IWUSR, proc_pid_sched_wake_up_idle_operations),

#endif

#ifdef CONFIG_SCHED_HMP

	REG("sched_init_task_load",      S_IRUGO|S_IWUSR, proc_pid_sched_init_task_load_operations),

#endif

include/linux/sched.h

+3 −0
Original line number Diff line number Diff line
@@ -1913,6 +1913,9 @@ sched_set_cpu_cstate(int cpu, int cstate, int wakeup_energy, int wakeup_latency) 
}

#endif



extern int sched_set_wake_up_idle(struct task_struct *p, int wake_up_idle);

extern u32 sched_get_wake_up_idle(struct task_struct *p);



#ifdef CONFIG_SCHED_HMP



extern int sched_set_boost(int enable);

kernel/sched/fair.c

+24 −1
Original line number Diff line number Diff line
@@ -82,7 +82,7 @@ unsigned int sysctl_sched_child_runs_first __read_mostly; 
/*

 * Controls whether, when SD_SHARE_PKG_RESOURCES is on, if all

 * tasks go to idle CPUs when woken. If this is off, note that the

 * per-task flag PF_WAKE_ON_IDLE can still cause a task to go to an

 * per-task flag PF_WAKE_UP_IDLE can still cause a task to go to an

 * idle CPU upon being woken.

 */

unsigned int __read_mostly sysctl_sched_wake_to_idle;
@@ -1128,6 +1128,29 @@ static inline void update_cfs_shares(struct cfs_rq *cfs_rq) 
}

#endif /* CONFIG_FAIR_GROUP_SCHED */



#ifdef CONFIG_SMP



u32 sched_get_wake_up_idle(struct task_struct *p)

{

	u32 enabled = p->flags & PF_WAKE_UP_IDLE;



	return !!enabled;

}



int sched_set_wake_up_idle(struct task_struct *p, int wake_up_idle)

{

	int enable = !!wake_up_idle;



	if (enable)

		p->flags |= PF_WAKE_UP_IDLE;

	else

		p->flags &= ~PF_WAKE_UP_IDLE;



	return 0;

}



#endif	/* CONFIG_SMP */



/* Only depends on SMP, FAIR_GROUP_SCHED may be removed when useful in lb */

#if defined(CONFIG_SMP) && defined(CONFIG_FAIR_GROUP_SCHED)

/*