[PATCH] O6int for interactivity

Con Kolivas
2003-07-16T14:13:12Z

O*int patches trying to improve the interactivity of the 2.5/6 scheduler for
desktops. It appears possible to do this without moving to nanosecond
resolution.

This one makes a massive difference... Please test this to death.

Changes:
The big change is in the way sleep_avg is incremented. Any amount of sleep
will now raise you by at least one priority with each wakeup. This causes
massive differences to startup time, extremely rapid conversion to interactive
state, and recovery from non-interactive state rapidly as well (prevents X
stalling after thrashing around under high loads for many seconds).

The sleep buffer was dropped to just 10ms. This has the effect of causing mild
round robinning of very interactive tasks if they run for more than 10ms. The
requeuing was changed from (unlikely()) to an ordinary if.. branch as this
will be hit much more now.

MAX_BONUS as a #define was made easier to understand

Idle tasks were made slightly less interactive to prevent cpu hogs from
becoming interactive on their very first wakeup.

Con

This patch-O6int-0307170012 applies on top of 2.6.0-test1-mm1 and can be found
here:
http://kernel.kolivas.org/2.5

and here:

--- linux-2.6.0-test1-mm1/kernel/sched.c 2003-07-16 20:27:32.000000000 +1000
+++ linux-2.6.0-testck1/kernel/sched.c 2003-07-17 00:13:24.000000000 +1000
@@ -76,9 +76,9 @@
#define MIN_SLEEP_AVG (HZ)
#define MAX_SLEEP_AVG (10*HZ)
#define STARVATION_LIMIT (10*HZ)
-#define SLEEP_BUFFER (HZ/20)
+#define SLEEP_BUFFER (HZ/100)
#define NODE_THRESHOLD 125
-#define MAX_BONUS ((MAX_USER_PRIO - MAX_RT_PRIO) * PRIO_BONUS_RATIO / 100)
+#define MAX_BONUS (40 * PRIO_BONUS_RATIO / 100)

/*
* If a task is 'interactive' then we reinsert it in the active
@@ -399,7 +399,7 @@ static inline void activate_task(task_t
*/
if (sleep_time > MIN_SLEEP_AVG){
p->avg_start = jiffies - MIN_SLEEP_AVG;
- p->sleep_avg = MIN_SLEEP_AVG * (MAX_BONUS - INTERACTIVE_DELTA - 1) /
+ p->sleep_avg = MIN_SLEEP_AVG * (MAX_BONUS - INTERACTIVE_DELTA - 2) /
MAX_BONUS;
} else {
/*
@@ -413,14 +413,10 @@ static inline void activate_task(task_t
p->sleep_avg += sleep_time;

/*
- * Give a bonus to tasks that wake early on to prevent
- * the problem of the denominator in the bonus equation
- * from continually getting larger.
+ * Processes that sleep get pushed to a higher priority
+ * each time they sleep
*/
- if ((runtime - MIN_SLEEP_AVG) < MAX_SLEEP_AVG)
- p->sleep_avg += (runtime - p->sleep_avg) *
- (MAX_SLEEP_AVG + MIN_SLEEP_AVG - runtime) *
- (MAX_BONUS - INTERACTIVE_DELTA) / MAX_BONUS / MAX_SLEEP_AVG;
+ p->sleep_avg = (p->sleep_avg * MAX_BONUS / runtime + 1) * runtime / MAX_BONUS;

/*
* Keep a small buffer of SLEEP_BUFFER sleep_avg to
@@ -1311,7 +1307,7 @@ void scheduler_tick(int user_ticks, int
enqueue_task(p, rq->expired);
} else
enqueue_task(p, rq->active);
- } else if (unlikely(p->prio < effective_prio(p))){
+ } else if (p->prio < effective_prio(p)){
/*
* Tasks that have lowered their priority are put to the end
* of the active array with their remaining timeslice