From: Ingo Molnar <mingo@elte.hu>
* Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> Increasing priority (negative nice) doesn't have much impact. -20 CPU
> hog only gets about double the CPU of a 0 priority CPU hog and only
> about 120% the CPU time of a nice -10 hog.
this is a property of the base scheduler as well.
We can do a nonlinear timeslice distribution trivially - the attached
patch implements the following timeslice distribution ontop of
2.6.8-rc3-mm1:
[ -20 ... 0 ... 19 ] => [800ms ... 100ms ... 5ms]
the nice-20/nice+19 ratio is now 1:160 - sufficient for all aspects.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/kernel/sched.c | 31 ++++++++++++++-----------------
1 files changed, 14 insertions(+), 17 deletions(-)
diff -puN kernel/sched.c~sched-nonlinear-timeslicespatch kernel/sched.c
--- 25/kernel/sched.c~sched-nonlinear-timeslicespatch 2004-08-06 02:42:28.891434632 -0700
+++ 25-akpm/kernel/sched.c 2004-08-06 02:42:28.898433568 -0700
@@ -70,8 +70,6 @@
#define USER_PRIO(p) ((p)-MAX_RT_PRIO)
#define TASK_USER_PRIO(p) USER_PRIO((p)->static_prio)
#define MAX_USER_PRIO (USER_PRIO(MAX_PRIO))
-#define AVG_TIMESLICE (MIN_TIMESLICE + ((MAX_TIMESLICE - MIN_TIMESLICE) *\
- (MAX_PRIO-1-NICE_TO_PRIO(0))/(MAX_USER_PRIO - 1)))
/*
* Some helpers for converting nanosecond timing to jiffy resolution
@@ -83,11 +81,11 @@
* These are the 'tuning knobs' of the scheduler:
*
* Minimum timeslice is 5 msecs (or 1 jiffy, whichever is larger),
- * default timeslice is 100 msecs, maximum timeslice is 200 msecs.
+ * default timeslice is 100 msecs, maximum timeslice is 800 msecs.
* Timeslices get refilled after they expire.
*/
#define MIN_TIMESLICE max(5 * HZ / 1000, 1)
-#define MAX_TIMESLICE (200 * HZ / 1000)
+#define DEF_TIMESLICE (100 * HZ / 1000)
#define ON_RUNQUEUE_WEIGHT 30
#define CHILD_PENALTY 95
#define PARENT_PENALTY 100
@@ -95,7 +93,7 @@
#define PRIO_BONUS_RATIO 25
#define MAX_BONUS (MAX_USER_PRIO * PRIO_BONUS_RATIO / 100)
#define INTERACTIVE_DELTA 2
-#define MAX_SLEEP_AVG (AVG_TIMESLICE * MAX_BONUS)
+#define MAX_SLEEP_AVG (DEF_TIMESLICE * MAX_BONUS)
#define STARVATION_LIMIT (MAX_SLEEP_AVG)
#define NS_MAX_SLEEP_AVG (JIFFIES_TO_NS(MAX_SLEEP_AVG))
#define CREDIT_LIMIT 100
@@ -164,25 +162,24 @@
((p)->prio < (rq)->curr->prio)
/*
- * BASE_TIMESLICE scales user-nice values [ -20 ... 19 ]
- * to time slice values.
+ * task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ]
+ * to time slice values: [800ms ... 100ms ... 5ms]
*
* The higher a thread's priority, the bigger timeslices
* it gets during one round of execution. But even the lowest
* priority thread gets MIN_TIMESLICE worth of execution time.
- *
- * task_timeslice() is the interface that is used by the scheduler.
*/
-#define BASE_TIMESLICE(p) \
- max(MAX_TIMESLICE * (MAX_PRIO - (p)->static_prio) / (MAX_USER_PRIO), \
- MIN_TIMESLICE)
+#define SCALE_PRIO(x, prio) \
+ max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO/2), MIN_TIMESLICE)
static unsigned int task_timeslice(task_t *p)
{
- return BASE_TIMESLICE(p);
+ if (p->static_prio < NICE_TO_PRIO(0))
+ return SCALE_PRIO(DEF_TIMESLICE*4, p->static_prio);
+ else
+ return SCALE_PRIO(DEF_TIMESLICE, p->static_prio);
}
-
#define task_hot(p, now, sd) ((now) - (p)->timestamp < (sd)->cache_hot_time)
enum idle_type
@@ -793,7 +790,7 @@ static void recalc_task_prio(task_t *p,
if (p->mm && p->activated != -1 &&
sleep_time > INTERACTIVE_SLEEP(p)) {
p->sleep_avg = JIFFIES_TO_NS(MAX_SLEEP_AVG -
- AVG_TIMESLICE);
+ DEF_TIMESLICE);
if (!HIGH_CREDIT(p))
p->interactive_credit++;
} else {
@@ -1435,8 +1432,8 @@ void fastcall sched_exit(task_t * p)
rq = task_rq_lock(p->parent, &flags);
if (p->first_time_slice) {
p->parent->time_slice += p->time_slice;
- if (unlikely(p->parent->time_slice > MAX_TIMESLICE))
- p->parent->time_slice = MAX_TIMESLICE;
+ if (unlikely(p->parent->time_slice > task_timeslice(p)))
+ p->parent->time_slice = task_timeslice(p);
}
if (p->sleep_avg < p->parent->sleep_avg)
p->parent->sleep_avg = p->parent->sleep_avg /
_