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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2009-09-11 06:31:23 -0400
committerIngo Molnar <mingo@elte.hu>2009-09-15 10:01:03 -0400
commite26af0e8b2c9916f1e8a12ddaf52057bbe8ff600 (patch)
tree0e885c5891b8d43af27d00a5702600ee15d113d3
parent3cb63d527f76e25dbccce4f577f21aecfa2abac7 (diff)
sched: Add come comments to the sched features
Add text... Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/sched_features.h93
1 files changed, 85 insertions, 8 deletions
diff --git a/kernel/sched_features.h b/kernel/sched_features.h
index 6174c1233993..891ea0f72b46 100644
--- a/kernel/sched_features.h
+++ b/kernel/sched_features.h
@@ -1,19 +1,96 @@
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 */
1SCHED_FEAT(NEW_FAIR_SLEEPERS, 0) 6SCHED_FEAT(NEW_FAIR_SLEEPERS, 0)
7
8/*
9 * By not normalizing the sleep time, heavy tasks get an effective
10 * longer period, and lighter task an effective shorter period they
11 * are considered running.
12 */
2SCHED_FEAT(NORMALIZED_SLEEPER, 0) 13SCHED_FEAT(NORMALIZED_SLEEPER, 0)
3SCHED_FEAT(ADAPTIVE_GRAN, 1) 14
4SCHED_FEAT(WAKEUP_PREEMPT, 1) 15/*
16 * Place new tasks ahead so that they do not starve already running
17 * tasks
18 */
5SCHED_FEAT(START_DEBIT, 1) 19SCHED_FEAT(START_DEBIT, 1)
20
21/*
22 * Should wakeups try to preempt running tasks.
23 */
24SCHED_FEAT(WAKEUP_PREEMPT, 1)
25
26/*
27 * Compute wakeup_gran based on task behaviour, clipped to
28 * [0, sched_wakeup_gran_ns]
29 */
30SCHED_FEAT(ADAPTIVE_GRAN, 1)
31
32/*
33 * When converting the wakeup granularity to virtual time, do it such
34 * that heavier tasks preempting a lighter task have an edge.
35 */
36SCHED_FEAT(ASYM_GRAN, 1)
37
38/*
39 * Always wakeup-preempt SYNC wakeups, see SYNC_WAKEUPS.
40 */
41SCHED_FEAT(WAKEUP_SYNC, 0)
42
43/*
44 * Wakeup preempt based on task behaviour. Tasks that do not overlap
45 * don't get preempted.
46 */
47SCHED_FEAT(WAKEUP_OVERLAP, 0)
48
49/*
50 * Use the SYNC wakeup hint, pipes and the likes use this to indicate
51 * the remote end is likely to consume the data we just wrote, and
52 * therefore has cache benefit from being placed on the same cpu, see
53 * also AFFINE_WAKEUPS.
54 */
55SCHED_FEAT(SYNC_WAKEUPS, 1)
56
57/*
58 * Based on load and program behaviour, see if it makes sense to place
59 * a newly woken task on the same cpu as the task that woke it --
60 * improve cache locality. Typically used with SYNC wakeups as
61 * generated by pipes and the like, see also SYNC_WAKEUPS.
62 */
6SCHED_FEAT(AFFINE_WAKEUPS, 1) 63SCHED_FEAT(AFFINE_WAKEUPS, 1)
64
65/*
66 * Prefer to schedule the task we woke last (assuming it failed
67 * wakeup-preemption), since its likely going to consume data we
68 * touched, increases cache locality.
69 */
70SCHED_FEAT(NEXT_BUDDY, 1)
71
72/*
73 * Prefer to schedule the task that ran last (when we did
74 * wake-preempt) as that likely will touch the same data, increases
75 * cache locality.
76 */
77SCHED_FEAT(LAST_BUDDY, 1)
78
79/*
80 * Consider buddies to be cache hot, decreases the likelyness of a
81 * cache buddy being migrated away, increases cache locality.
82 */
7SCHED_FEAT(CACHE_HOT_BUDDY, 1) 83SCHED_FEAT(CACHE_HOT_BUDDY, 1)
8SCHED_FEAT(SYNC_WAKEUPS, 1) 84
9SCHED_FEAT(HRTICK, 0) 85SCHED_FEAT(HRTICK, 0)
10SCHED_FEAT(DOUBLE_TICK, 0) 86SCHED_FEAT(DOUBLE_TICK, 0)
11SCHED_FEAT(ASYM_GRAN, 1)
12SCHED_FEAT(LB_BIAS, 1) 87SCHED_FEAT(LB_BIAS, 1)
13SCHED_FEAT(LB_WAKEUP_UPDATE, 1) 88SCHED_FEAT(LB_WAKEUP_UPDATE, 1)
14SCHED_FEAT(ASYM_EFF_LOAD, 1) 89SCHED_FEAT(ASYM_EFF_LOAD, 1)
15SCHED_FEAT(WAKEUP_SYNC, 0) 90
16SCHED_FEAT(WAKEUP_OVERLAP, 0) 91/*
17SCHED_FEAT(NEXT_BUDDY, 1) 92 * Spin-wait on mutex acquisition when the mutex owner is running on
18SCHED_FEAT(LAST_BUDDY, 1) 93 * another cpu -- assumes that when the owner is running, it will soon
94 * release the lock. Decreases scheduling overhead.
95 */
19SCHED_FEAT(OWNER_SPIN, 1) 96SCHED_FEAT(OWNER_SPIN, 1)