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Commit e79f447a authored by Vikram Mulukutla's avatar Vikram Mulukutla Committed by Joel Fernandes
Browse files

sched: walt: Correct WALT window size initialization 



It is preferable that WALT window rollover occurs just
before a tick, since the tick is an opportune moment
to record a complete window's statistics, as well as report
those stats to the cpu frequency governor. When CONFIG_HZ
results in a TICK_NSEC that isn't a integral number, this
requirement may be violated. Account for this by reducing
the WALT window size to the nearest multiple of TICK_NSEC.

Commit d368c6fa ("sched: walt: fix window misalignment
when HZ=300") attempted to do this but WALT isn't using
MIN_SCHED_RAVG_WINDOW as the window size and the patch was
doing nothing.

Also, change the type of 'walt_disabled' to bool and warn
if an invalid window size causes WALT to be disabled.

Change-Id: Ie3dcfc21a3df4408254ca1165a355bbe391ed5c7
Signed-off-by: default avatarVikram Mulukutla <markivx@codeaurora.org>
parent 38ddcff8

include/trace/events/sched.h

+1 −1
Original line number Diff line number Diff line
@@ -642,7 +642,7 @@ TRACE_EVENT(sched_contrib_scale_f, 
extern unsigned int sysctl_sched_use_walt_cpu_util;

extern unsigned int sysctl_sched_use_walt_task_util;

extern unsigned int walt_ravg_window;

extern unsigned int walt_disabled;

extern bool walt_disabled;

#endif



/*

kernel/sched/sched.h

+1 −1
Original line number Diff line number Diff line
@@ -1560,7 +1560,7 @@ static inline unsigned long capacity_orig_of(int cpu) 


extern unsigned int sysctl_sched_use_walt_cpu_util;

extern unsigned int walt_ravg_window;

extern unsigned int walt_disabled;

extern bool walt_disabled;



/*

 * cpu_util returns the amount of capacity of a CPU that is used by CFS

kernel/sched/walt.c

+28 −18
Original line number Diff line number Diff line
@@ -41,25 +41,17 @@ static __read_mostly unsigned int walt_io_is_busy = 0; 


unsigned int sysctl_sched_walt_init_task_load_pct = 15;



/* 1 -> use PELT based load stats, 0 -> use window-based load stats */

unsigned int __read_mostly walt_disabled = 0;

/* true -> use PELT based load stats, false -> use window-based load stats */

bool __read_mostly walt_disabled = false;



/* Window size (in ns) */

__read_mostly unsigned int walt_ravg_window = 20000000;



/* Min window size (in ns) = 10ms */

#ifdef CONFIG_HZ_300

/*

 * Tick interval becomes to 3333333 due to

 * rounding error when HZ=300.

 * Window size (in ns). Adjust for the tick size so that the window

 * rollover occurs just before the tick boundary.

 */

#define MIN_SCHED_RAVG_WINDOW (3333333 * 6)

#else

#define MIN_SCHED_RAVG_WINDOW 10000000

#endif



/* Max window size (in ns) = 1s */

#define MAX_SCHED_RAVG_WINDOW 1000000000

__read_mostly unsigned int walt_ravg_window =

					    (20000000 / TICK_NSEC) * TICK_NSEC;

#define MIN_SCHED_RAVG_WINDOW ((10000000 / TICK_NSEC) * TICK_NSEC)

#define MAX_SCHED_RAVG_WINDOW ((1000000000 / TICK_NSEC) * TICK_NSEC)



static unsigned int sync_cpu;

static ktime_t ktime_last;
@@ -180,10 +172,28 @@ static int exiting_task(struct task_struct *p) 


static int __init set_walt_ravg_window(char *str)

{

	unsigned int adj_window;

	bool no_walt = walt_disabled;



	get_option(&str, &walt_ravg_window);



	walt_disabled = (walt_ravg_window < MIN_SCHED_RAVG_WINDOW ||

	/* Adjust for CONFIG_HZ */

	adj_window = (walt_ravg_window / TICK_NSEC) * TICK_NSEC;



	/* Warn if we're a bit too far away from the expected window size */

	WARN(adj_window < walt_ravg_window - NSEC_PER_MSEC,

	     "tick-adjusted window size %u, original was %u\n", adj_window,

	     walt_ravg_window);



	walt_ravg_window = adj_window;



	walt_disabled = walt_disabled ||

			(walt_ravg_window < MIN_SCHED_RAVG_WINDOW ||

			 walt_ravg_window > MAX_SCHED_RAVG_WINDOW);



	WARN(!no_walt && walt_disabled,

	     "invalid window size, disabling WALT\n");



	return 0;

}

kernel/sched/walt.h

+1 −1
Original line number Diff line number Diff line
@@ -59,6 +59,6 @@ static inline u64 walt_ktime_clock(void) { return 0; } 


#endif /* CONFIG_SCHED_WALT */



extern unsigned int walt_disabled;

extern bool walt_disabled;



#endif