[linux-block.git] / kernel / sched_features.h

/*
 * Disregards a certain amount of sleep time (sched_latency_ns) and
 * considers the task to be running during that period. This gives it
 * a service deficit on wakeup, allowing it to run sooner.
 */
SCHED_FEAT(FAIR_SLEEPERS, 1)

/*
 * Only give sleepers 50% of their service deficit. This allows
 * them to run sooner, but does not allow tons of sleepers to
 * rip the spread apart.
 */
SCHED_FEAT(GENTLE_FAIR_SLEEPERS, 1)

/*
 * By not normalizing the sleep time, heavy tasks get an effective
 * longer period, and lighter task an effective shorter period they
 * are considered running.
 */
SCHED_FEAT(NORMALIZED_SLEEPER, 0)

/*
 * Place new tasks ahead so that they do not starve already running
 * tasks
 */
SCHED_FEAT(START_DEBIT, 1)

/*
 * Should wakeups try to preempt running tasks.
 */
SCHED_FEAT(WAKEUP_PREEMPT, 1)

/*
 * Compute wakeup_gran based on task behaviour, clipped to
 *  [0, sched_wakeup_gran_ns]
 */
SCHED_FEAT(ADAPTIVE_GRAN, 1)

/*
 * When converting the wakeup granularity to virtual time, do it such
 * that heavier tasks preempting a lighter task have an edge.
 */
SCHED_FEAT(ASYM_GRAN, 1)

/*
 * Always wakeup-preempt SYNC wakeups, see SYNC_WAKEUPS.
 */
SCHED_FEAT(WAKEUP_SYNC, 0)

/*
 * Wakeup preempt based on task behaviour. Tasks that do not overlap
 * don't get preempted.
 */
SCHED_FEAT(WAKEUP_OVERLAP, 0)

/*
 * Wakeup preemption towards tasks that run short
 */
SCHED_FEAT(WAKEUP_RUNNING, 0)

/*
 * Use the SYNC wakeup hint, pipes and the likes use this to indicate
 * the remote end is likely to consume the data we just wrote, and
 * therefore has cache benefit from being placed on the same cpu, see
 * also AFFINE_WAKEUPS.
 */
SCHED_FEAT(SYNC_WAKEUPS, 1)

/*
 * Based on load and program behaviour, see if it makes sense to place
 * a newly woken task on the same cpu as the task that woke it --
 * improve cache locality. Typically used with SYNC wakeups as
 * generated by pipes and the like, see also SYNC_WAKEUPS.
 */
SCHED_FEAT(AFFINE_WAKEUPS, 1)

/*
 * Weaken SYNC hint based on overlap
 */
SCHED_FEAT(SYNC_LESS, 1)

/*
 * Add SYNC hint based on overlap
 */
SCHED_FEAT(SYNC_MORE, 0)

/*
 * Prefer to schedule the task we woke last (assuming it failed
 * wakeup-preemption), since its likely going to consume data we
 * touched, increases cache locality.
 */
SCHED_FEAT(NEXT_BUDDY, 0)

/*
 * Prefer to schedule the task that ran last (when we did
 * wake-preempt) as that likely will touch the same data, increases
 * cache locality.
 */
SCHED_FEAT(LAST_BUDDY, 1)

/*
 * Consider buddies to be cache hot, decreases the likelyness of a
 * cache buddy being migrated away, increases cache locality.
 */
SCHED_FEAT(CACHE_HOT_BUDDY, 1)

/*
 * Use arch dependent cpu power functions
 */
SCHED_FEAT(ARCH_POWER, 0)

SCHED_FEAT(HRTICK, 0)
SCHED_FEAT(DOUBLE_TICK, 0)
SCHED_FEAT(LB_BIAS, 1)
SCHED_FEAT(LB_SHARES_UPDATE, 1)
SCHED_FEAT(ASYM_EFF_LOAD, 1)

/*
 * Spin-wait on mutex acquisition when the mutex owner is running on
 * another cpu -- assumes that when the owner is running, it will soon
 * release the lock. Decreases scheduling overhead.
 */
SCHED_FEAT(OWNER_SPIN, 1)
Commit	Line	Data
e26af0e8 PZ	1	/*
	2	* Disregards a certain amount of sleep time (sched_latency_ns) and
	3	* considers the task to be running during that period. This gives it
	4	* a service deficit on wakeup, allowing it to run sooner.
	5	*/
51e0304c IM	6	SCHED_FEAT(FAIR_SLEEPERS, 1)
	7
	8	/*
	9	* Only give sleepers 50% of their service deficit. This allows
	10	* them to run sooner, but does not allow tons of sleepers to
	11	* rip the spread apart.
	12	*/
	13	SCHED_FEAT(GENTLE_FAIR_SLEEPERS, 1)
e26af0e8 PZ	14
	15	/*
	16	* By not normalizing the sleep time, heavy tasks get an effective
	17	* longer period, and lighter task an effective shorter period they
	18	* are considered running.
	19	*/
e52fb7c0	20	SCHED_FEAT(NORMALIZED_SLEEPER, 0)
e26af0e8 PZ	21
	22	/*
	23	* Place new tasks ahead so that they do not starve already running
	24	* tasks
	25	*/
f00b45c1	26	SCHED_FEAT(START_DEBIT, 1)
e26af0e8 PZ	27
	28	/*
	29	* Should wakeups try to preempt running tasks.
	30	*/
	31	SCHED_FEAT(WAKEUP_PREEMPT, 1)
	32
	33	/*
	34	* Compute wakeup_gran based on task behaviour, clipped to
	35	* [0, sched_wakeup_gran_ns]
	36	*/
	37	SCHED_FEAT(ADAPTIVE_GRAN, 1)
	38
	39	/*
	40	* When converting the wakeup granularity to virtual time, do it such
	41	* that heavier tasks preempting a lighter task have an edge.
	42	*/
	43	SCHED_FEAT(ASYM_GRAN, 1)
	44
	45	/*
	46	* Always wakeup-preempt SYNC wakeups, see SYNC_WAKEUPS.
	47	*/
	48	SCHED_FEAT(WAKEUP_SYNC, 0)
	49
	50	/*
	51	* Wakeup preempt based on task behaviour. Tasks that do not overlap
	52	* don't get preempted.
	53	*/
	54	SCHED_FEAT(WAKEUP_OVERLAP, 0)
	55
ad4b78bb PZ	56	/*
	57	* Wakeup preemption towards tasks that run short
	58	*/
	59	SCHED_FEAT(WAKEUP_RUNNING, 0)
	60
e26af0e8 PZ	61	/*
	62	* Use the SYNC wakeup hint, pipes and the likes use this to indicate
	63	* the remote end is likely to consume the data we just wrote, and
	64	* therefore has cache benefit from being placed on the same cpu, see
	65	* also AFFINE_WAKEUPS.
	66	*/
	67	SCHED_FEAT(SYNC_WAKEUPS, 1)
	68
	69	/*
	70	* Based on load and program behaviour, see if it makes sense to place
	71	* a newly woken task on the same cpu as the task that woke it --
	72	* improve cache locality. Typically used with SYNC wakeups as
	73	* generated by pipes and the like, see also SYNC_WAKEUPS.
	74	*/
f00b45c1	75	SCHED_FEAT(AFFINE_WAKEUPS, 1)
e26af0e8	76
e69b0f1b PZ	77	/*
	78	* Weaken SYNC hint based on overlap
	79	*/
	80	SCHED_FEAT(SYNC_LESS, 1)
	81
	82	/*
	83	* Add SYNC hint based on overlap
	84	*/
	85	SCHED_FEAT(SYNC_MORE, 0)
	86
e26af0e8 PZ	87	/*
	88	* Prefer to schedule the task we woke last (assuming it failed
	89	* wakeup-preemption), since its likely going to consume data we
	90	* touched, increases cache locality.
	91	*/
0ec9fab3	92	SCHED_FEAT(NEXT_BUDDY, 0)
e26af0e8 PZ	93
	94	/*
	95	* Prefer to schedule the task that ran last (when we did
	96	* wake-preempt) as that likely will touch the same data, increases
	97	* cache locality.
	98	*/
	99	SCHED_FEAT(LAST_BUDDY, 1)
	100
	101	/*
	102	* Consider buddies to be cache hot, decreases the likelyness of a
	103	* cache buddy being migrated away, increases cache locality.
	104	*/
f00b45c1	105	SCHED_FEAT(CACHE_HOT_BUDDY, 1)
e26af0e8	106
8e6598af PZ	107	/*
	108	* Use arch dependent cpu power functions
	109	*/
	110	SCHED_FEAT(ARCH_POWER, 0)
	111
0c4b83da	112	SCHED_FEAT(HRTICK, 0)
f00b45c1	113	SCHED_FEAT(DOUBLE_TICK, 0)
efc2dead	114	SCHED_FEAT(LB_BIAS, 1)
3b640894	115	SCHED_FEAT(LB_SHARES_UPDATE, 1)
f5bfb7d9	116	SCHED_FEAT(ASYM_EFF_LOAD, 1)
e26af0e8 PZ	117
	118	/*
	119	* Spin-wait on mutex acquisition when the mutex owner is running on
	120	* another cpu -- assumes that when the owner is running, it will soon
	121	* release the lock. Decreases scheduling overhead.
	122	*/
0d66bf6d	123	SCHED_FEAT(OWNER_SPIN, 1)