readahead: data structure and routines

[linux-2.6-omap-h63xx.git] / kernel / sched.c

diff --git a/kernel/sched.c b/kernel/sched.c
index 3332bbb5d5cf96d3677cbd5c20737c77a45bdf7f..cb31fb4a1379e23b0628795d5e1bfd64c6031bf0 100644 (file)
--- 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
@@ -4903,8 +4912,6 @@ static int migration_thread(void *data)
                struct migration_req *req;
                struct list_head *head;
 
-               try_to_freeze();
-
                spin_lock_irq(&rq->lock);
 
                if (cpu_is_offline(cpu)) {
@@ -5138,7 +5145,6 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
                p = kthread_create(migration_thread, hcpu, "migration/%d", cpu);
                if (IS_ERR(p))
                        return NOTIFY_BAD;
-               p->flags |= PF_NOFREEZE;
                kthread_bind(p, cpu);
                /* Must be high prio: stop_machine expects to yield to it. */
                rq = task_rq_lock(p, &flags);