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Commit 3a7ecda2 authored by Joonwoo Park's avatar Joonwoo Park
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Revert "sched: Use only partial wait time as task demand" 



This reverts commit 0e2092e4 ("sched: Use only partial wait time as
task demand") as it causes performance regression.

Change-Id: I3917858be98530807c479fc31eb76c0f22b4ea89
Signed-off-by: default avatarJoonwoo Park <joonwoop@codeaurora.org>
parent 851a0a45

Documentation/scheduler/sched-hmp.txt

+1 −10
Original line number Diff line number Diff line
@@ -1350,17 +1350,8 @@ Appears at: /proc/sys/kernel/sched_account_wait_time 


Default value: 1



This controls whether a tasks wait time is accounted as its demand for cpu

This controls whether a task's wait time is accounted as its demand for cpu

and thus the values found in its sum, sum_history[] and demand attributes.

The load tracking algorithm only considers part of a tasks wait time as its

demand. The portion of wait time accounted as demand is determined by each

tasks percent load, i.e. a task that waits for 10ms and has 60 % task load,

only 6 ms of the wait will contribute to task demand. This approach is fair

as the scheduler tries to determine how much of its wait time would a task

actually have been using the CPU if it had been executing. It ensures that

tasks with high demand continue to see most of the benefits of accounting

wait time as busy time, however, lower demand tasks don't experience a

disproportionately high boost to demand.



*** 7.16 sched_freq_account_wait_time

kernel/sched/core.c

+10 −26
Original line number Diff line number Diff line
@@ -1631,23 +1631,19 @@ static inline void update_cpu_busy_time(struct task_struct *p, struct rq *rq, 


static int account_busy_for_task_demand(struct task_struct *p, int event)

{

	/* No need to bother updating task demand for exiting tasks

	 * or the idle task. */

	if (exiting_task(p) || is_idle_task(p))

		return 0;



	/*

	 * When a task is waking up it is completing a segment of non-busy

	/* When a task is waking up it is completing a segment of non-busy

	 * time. Likewise, if wait time is not treated as busy time, then

	 * when a task begins to run or is migrated, it is not running and

	 * is completing a segment of non-busy time.

	 */

	 * is completing a segment of non-busy time. */

	if (event == TASK_WAKE || (!sched_account_wait_time &&

			 (event == PICK_NEXT_TASK || event == TASK_MIGRATE)))

		return 0;



	/*

	 * We are left with TASK_UPDATE, IRQ_UPDATE, PUT_PREV_TASK and

	 * wait time being accounted as busy time.

	 */

	return 1;

}
@@ -1719,15 +1715,6 @@ static void add_to_task_demand(struct rq *rq, struct task_struct *p, 
		p->ravg.sum = sched_ravg_window;

}



static u64 wait_adjust(struct task_struct *p, u64 delta, int event)

{

	/* We already know that wait time counts as busy time. */

	if (event == PICK_NEXT_TASK || event == TASK_MIGRATE)

		return div64_u64(delta * task_load(p), max_task_load());



	return delta;

}



/*

 * Account cpu demand of task and/or update task's cpu demand history

 *
@@ -1802,8 +1789,7 @@ static void update_task_demand(struct task_struct *p, struct rq *rq, 
	if (!new_window) {

		/* The simple case - busy time contained within the existing

		 * window. */

		add_to_task_demand(rq, p, wait_adjust(p,

				wallclock - mark_start, event));

		add_to_task_demand(rq, p, wallclock - mark_start);

		return;

	}
@@ -1814,14 +1800,13 @@ static void update_task_demand(struct task_struct *p, struct rq *rq, 
	window_start -= (u64)nr_full_windows * (u64)window_size;



	/* Process (window_start - mark_start) first */

	add_to_task_demand(rq, p,

		wait_adjust(p, window_start - mark_start, event));

	add_to_task_demand(rq, p, window_start - mark_start);



	/* Push new sample(s) into task's demand history */

	update_history(rq, p, p->ravg.sum, 1, event);

	if (nr_full_windows)

		update_history(rq, p, scale_exec_time(wait_adjust(p,

		window_size, event), rq), nr_full_windows, event);

		update_history(rq, p, scale_exec_time(window_size, rq),

			       nr_full_windows, event);



	/* Roll window_start back to current to process any remainder

	 * in current window. */
@@ -1829,8 +1814,7 @@ static void update_task_demand(struct task_struct *p, struct rq *rq, 


	/* Process (wallclock - window_start) next */

	mark_start = window_start;

	add_to_task_demand(rq, p,

		wait_adjust(p, wallclock - mark_start, event));

	add_to_task_demand(rq, p, wallclock - mark_start);

}



/* Reflect task activity on its demand and cpu's busy time statistics */

kernel/sched/fair.c

+1 −1
Original line number Diff line number Diff line
@@ -2449,7 +2449,7 @@ unsigned int __read_mostly sysctl_sched_init_task_load_pct = 15; 
unsigned int __read_mostly sysctl_sched_min_runtime = 0; /* 0 ms */

u64 __read_mostly sched_min_runtime = 0; /* 0 ms */



unsigned int task_load(struct task_struct *p)

static inline unsigned int task_load(struct task_struct *p)

{

	if (sched_use_pelt)

		return p->se.avg.runnable_avg_sum_scaled;

kernel/sched/sched.h

+0 −1
Original line number Diff line number Diff line
@@ -913,7 +913,6 @@ extern unsigned int sched_heavy_task; 
extern unsigned int up_down_migrate_scale_factor;

extern void reset_cpu_hmp_stats(int cpu, int reset_cra);

extern void fixup_nr_big_small_task(int cpu, int reset_stats);

extern unsigned int task_load(struct task_struct *p);

extern unsigned int max_task_load(void);

extern void sched_account_irqtime(int cpu, struct task_struct *curr,

				 u64 delta, u64 wallclock);