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-rw-r--r--kernel/sched.c52
1 files changed, 27 insertions, 25 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 582faed3d36..cb146219d53 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -686,33 +686,35 @@ static inline void __activate_idle_task(task_t *p, runqueue_t *rq)
static int recalc_task_prio(task_t *p, unsigned long long now)
{
/* Caller must always ensure 'now >= p->timestamp' */
- unsigned long long __sleep_time = now - p->timestamp;
- unsigned long sleep_time;
+ unsigned long sleep_time = now - p->timestamp;
if (batch_task(p))
sleep_time = 0;
- else {
- if (__sleep_time > NS_MAX_SLEEP_AVG)
- sleep_time = NS_MAX_SLEEP_AVG;
- else
- sleep_time = (unsigned long)__sleep_time;
- }
if (likely(sleep_time > 0)) {
/*
- * User tasks that sleep a long time are categorised as
- * idle. They will only have their sleep_avg increased to a
- * level that makes them just interactive priority to stay
- * active yet prevent them suddenly becoming cpu hogs and
- * starving other processes.
+ * This ceiling is set to the lowest priority that would allow
+ * a task to be reinserted into the active array on timeslice
+ * completion.
*/
- if (p->mm && sleep_time > INTERACTIVE_SLEEP(p)) {
- unsigned long ceiling;
+ unsigned long ceiling = INTERACTIVE_SLEEP(p);
- ceiling = JIFFIES_TO_NS(MAX_SLEEP_AVG -
- DEF_TIMESLICE);
- if (p->sleep_avg < ceiling)
- p->sleep_avg = ceiling;
+ if (p->mm && sleep_time > ceiling && p->sleep_avg < ceiling) {
+ /*
+ * Prevents user tasks from achieving best priority
+ * with one single large enough sleep.
+ */
+ p->sleep_avg = ceiling;
+ /*
+ * Using INTERACTIVE_SLEEP() as a ceiling places a
+ * nice(0) task 1ms sleep away from promotion, and
+ * gives it 700ms to round-robin with no chance of
+ * being demoted. This is more than generous, so
+ * mark this sleep as non-interactive to prevent the
+ * on-runqueue bonus logic from intervening should
+ * this task not receive cpu immediately.
+ */
+ p->sleep_type = SLEEP_NONINTERACTIVE;
} else {
/*
* Tasks waking from uninterruptible sleep are
@@ -720,12 +722,12 @@ static int recalc_task_prio(task_t *p, unsigned long long now)
* are likely to be waiting on I/O
*/
if (p->sleep_type == SLEEP_NONINTERACTIVE && p->mm) {
- if (p->sleep_avg >= INTERACTIVE_SLEEP(p))
+ if (p->sleep_avg >= ceiling)
sleep_time = 0;
else if (p->sleep_avg + sleep_time >=
- INTERACTIVE_SLEEP(p)) {
- p->sleep_avg = INTERACTIVE_SLEEP(p);
- sleep_time = 0;
+ ceiling) {
+ p->sleep_avg = ceiling;
+ sleep_time = 0;
}
}
@@ -739,9 +741,9 @@ static int recalc_task_prio(task_t *p, unsigned long long now)
*/
p->sleep_avg += sleep_time;
- if (p->sleep_avg > NS_MAX_SLEEP_AVG)
- p->sleep_avg = NS_MAX_SLEEP_AVG;
}
+ if (p->sleep_avg > NS_MAX_SLEEP_AVG)
+ p->sleep_avg = NS_MAX_SLEEP_AVG;
}
return effective_prio(p);