diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched.c | 27 |
1 files changed, 18 insertions, 9 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 3332bbb5d5cf..1c8076676eb1 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -736,7 +736,9 @@ static void update_curr_load(struct rq *rq, u64 now) * * The "10% effect" is relative and cumulative: from _any_ nice level, * if you go up 1 level, it's -10% CPU usage, if you go down 1 level - * it's +10% CPU usage. + * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25. + * If a task goes up by ~10% and another task goes down by ~10% then + * the relative distance between them is ~25%.) */ static const int prio_to_weight[40] = { /* -20 */ 88818, 71054, 56843, 45475, 36380, 29104, 23283, 18626, 14901, 11921, @@ -746,15 +748,22 @@ static const int prio_to_weight[40] = { /* 10 */ 110, 87, 70, 56, 45, 36, 29, 23, 18, 15, }; +/* + * Inverse (2^32/x) values of the prio_to_weight[] array, precalculated. + * + * In cases where the weight does not change often, we can use the + * precalculated inverse to speed up arithmetics by turning divisions + * into multiplications: + */ static const u32 prio_to_wmult[40] = { - 48356, 60446, 75558, 94446, 118058, 147573, - 184467, 230589, 288233, 360285, 450347, - 562979, 703746, 879575, 1099582, 1374389, - 1717986, 2147483, 2684354, 3355443, 4194304, - 5244160, 6557201, 8196502, 10250518, 12782640, - 16025997, 19976592, 24970740, 31350126, 39045157, - 49367440, 61356675, 76695844, 95443717, 119304647, - 148102320, 186737708, 238609294, 286331153, +/* -20 */ 48356, 60446, 75558, 94446, 118058, +/* -15 */ 147573, 184467, 230589, 288233, 360285, +/* -10 */ 450347, 562979, 703746, 879575, 1099582, +/* -5 */ 1374389, 1717986, 2147483, 2684354, 3355443, +/* 0 */ 4194304, 5244160, 6557201, 8196502, 10250518, +/* 5 */ 12782640, 16025997, 19976592, 24970740, 31350126, +/* 10 */ 39045157, 49367440, 61356675, 76695844, 95443717, +/* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153, }; static inline void |