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After the recent discussions about the limitations on real time tasks and=20
normal users...
Wli coined the term "isochronous" (greek for same time) for a real time tas=
k=20
that was limited in it's timeslice but still guaranteed to run. I've decide=
d=20
to abuse this term and use it to name this new policy in this patch. This i=
s=20
neither real time, nor guaranteed.
What this patch does is introduce a new scheduler policy, SCHED_ISO. SI tas=
ks=20
get the maximum interactive bonus so they always get a dynamic priority of =
5=20
better than their static priority, but are penalised by having a smaller=20
timeslice. Most interactive tasks don't use up their full timeslice anyway.
Since most users and applications are not going to be altering scheduler=20
policies, this patch uses the current semantics in patches up to the O4int=
=20
patch I have posted previously (and in 2.5.75-mm1) to dynamically allocate=
=20
tasks as SI. This happens when their sleep avg hits MAX_SLEEP_AVG which is=
=20
extremely unlikely to happen for the wrong task. Unfortunately it also mean=
s=20
it takes at least 10 seconds. There are semantics in place to stop it=20
happening to idle tasks, tasks forking, and new children.
Anyway it's pretty rough around the edges since I slapped it together more =
to=20
prove it works, but appears to work as planned. The O*int patches appear to=
=20
be hitting a ceiling to their ability and this can help them further but I=
=20
need some feedback about it's usefulness, and appropriateness.=20
Without further feedback about the O*int patches I can't do much to develop=
=20
them further.
akpm: obviously this one is not to be included in -mm=20
Enough talk. The patch is attached below and available at:
http://kernel.kolivas.org/2.5
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--Boundary-00=_ycpD/PyPw4utzLz
Content-Type: text/x-diff;
charset="us-ascii";
name="patch-SI-0307111938"
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment;
filename="patch-SI-0307111938"
--- linux-2.5.74-mm3/include/linux/sched.h 2003-07-10 10:23:14.000000000 +1000
+++ linux-2.5.74-test/include/linux/sched.h 2003-07-11 19:35:37.000000000 +1000
@@ -125,6 +125,7 @@ extern unsigned long nr_iowait(void);
#define SCHED_NORMAL 0
#define SCHED_FIFO 1
#define SCHED_RR 2
+#define SCHED_ISO 3
struct sched_param {
int sched_priority;
--- linux-2.5.74-mm3/kernel/exit.c 2003-07-10 10:23:14.000000000 +1000
+++ linux-2.5.74-test/kernel/exit.c 2003-07-11 19:35:37.000000000 +1000
@@ -223,7 +223,7 @@ void reparent_to_init(void)
/* Set the exit signal to SIGCHLD so we signal init on exit */
current->exit_signal = SIGCHLD;
- if ((current->policy == SCHED_NORMAL) && (task_nice(current) < 0))
+ if ((current->policy == SCHED_NORMAL || current->policy == SCHED_ISO) && (task_nice(current) < 0))
set_user_nice(current, 0);
/* cpus_allowed? */
/* rt_priority? */
--- linux-2.5.74-mm3/kernel/sched.c 2003-07-11 19:43:34.000000000 +1000
+++ linux-2.5.74-test/kernel/sched.c 2003-07-11 19:38:09.000000000 +1000
@@ -76,7 +76,6 @@
#define MIN_SLEEP_AVG (HZ)
#define MAX_SLEEP_AVG (10*HZ)
#define STARVATION_LIMIT (10*HZ)
-#define SLEEP_BUFFER (HZ/20)
#define NODE_THRESHOLD 125
#define MAX_BONUS ((MAX_USER_PRIO - MAX_RT_PRIO) * PRIO_BONUS_RATIO / 100)
@@ -118,6 +117,8 @@
#define TASK_INTERACTIVE(p) \
((p)->prio <= (p)->static_prio - DELTA(p))
+#define iso_task(p) ((p)->policy == SCHED_ISO)
+
/*
* BASE_TIMESLICE scales user-nice values [ -20 ... 19 ]
* to time slice values.
@@ -134,7 +135,10 @@
static inline unsigned int task_timeslice(task_t *p)
{
- return BASE_TIMESLICE(p);
+ if (iso_task(p))
+ return (BASE_TIMESLICE(p) / 5 ? : 1);
+ else
+ return BASE_TIMESLICE(p);
}
/*
@@ -319,6 +323,10 @@ static inline void normalise_sleep(task_
p->sleep_avg = p->sleep_avg * MIN_SLEEP_AVG / old_avg_time;
p->avg_start = jiffies - MIN_SLEEP_AVG;
+
+ if (iso_task(p))
+ p->policy = SCHED_NORMAL;
+
}
/*
@@ -343,26 +351,32 @@ static int effective_prio(task_t *p)
if (rt_task(p))
return p->prio;
- sleep_period = jiffies - p->avg_start;
+ if (!iso_task(p)){
+ sleep_period = jiffies - p->avg_start;
- if (unlikely(!sleep_period))
- return p->static_prio;
+ if (unlikely(!sleep_period))
+ return p->static_prio;
- if (sleep_period > MAX_SLEEP_AVG)
- sleep_period = MAX_SLEEP_AVG;
+ if (sleep_period > MAX_SLEEP_AVG)
+ sleep_period = MAX_SLEEP_AVG;
- if (p->sleep_avg > sleep_period)
- sleep_period = p->sleep_avg;
+ if (p->sleep_avg > sleep_period)
+ sleep_period = p->sleep_avg;
- /*
- * The bonus is determined according to the accumulated
- * sleep avg over the duration the task has been running
- * until it reaches MAX_SLEEP_AVG. -ck
- */
- bonus = MAX_USER_PRIO*PRIO_BONUS_RATIO*p->sleep_avg/sleep_period/100 -
- MAX_USER_PRIO*PRIO_BONUS_RATIO/100/2;
+ /*
+ * The bonus is determined according to the accumulated
+ * sleep avg over the duration the task has been running
+ * until it reaches MAX_SLEEP_AVG. -ck
+ */
+ bonus = MAX_USER_PRIO*PRIO_BONUS_RATIO*p->sleep_avg/sleep_period/100 -
+ MAX_USER_PRIO*PRIO_BONUS_RATIO/100/2;
+
+ } else
+ bonus = MAX_USER_PRIO*PRIO_BONUS_RATIO/100 -
+ MAX_USER_PRIO*PRIO_BONUS_RATIO/100/2;
prio = p->static_prio - bonus;
+
if (prio < MAX_RT_PRIO)
prio = MAX_RT_PRIO;
if (prio > MAX_PRIO-1)
@@ -401,6 +415,8 @@ static inline void activate_task(task_t
p->avg_start = jiffies - MIN_SLEEP_AVG;
p->sleep_avg = MIN_SLEEP_AVG * (MAX_BONUS - INTERACTIVE_DELTA - 1) /
MAX_BONUS;
+ if (iso_task(p))
+ p->policy = SCHED_NORMAL;
} else {
/*
* This code gives a bonus to interactive tasks.
@@ -422,13 +438,11 @@ static inline void activate_task(task_t
(MAX_SLEEP_AVG + MIN_SLEEP_AVG - runtime) *
(MAX_BONUS - INTERACTIVE_DELTA) / MAX_BONUS / MAX_SLEEP_AVG;
- /*
- * Keep a small buffer of SLEEP_BUFFER sleep_avg to
- * prevent fully interactive tasks from becoming
- * lower priority with small bursts of cpu usage.
- */
- if (p->sleep_avg > (MAX_SLEEP_AVG + SLEEP_BUFFER))
- p->sleep_avg = MAX_SLEEP_AVG + SLEEP_BUFFER;
+ if (p->sleep_avg > MAX_SLEEP_AVG){
+ if (p->policy == SCHED_NORMAL)
+ p->policy = SCHED_ISO;
+ p->sleep_avg = MAX_SLEEP_AVG;
+ }
}
if (unlikely(p->avg_start > jiffies)){
@@ -1813,7 +1827,7 @@ static int setscheduler(pid_t pid, int p
else {
retval = -EINVAL;
if (policy != SCHED_FIFO && policy != SCHED_RR &&
- policy != SCHED_NORMAL)
+ policy != SCHED_NORMAL && policy != SCHED_ISO)
goto out_unlock;
}
@@ -1824,7 +1838,7 @@ static int setscheduler(pid_t pid, int p
retval = -EINVAL;
if (lp.sched_priority < 0 || lp.sched_priority > MAX_USER_RT_PRIO-1)
goto out_unlock;
- if ((policy == SCHED_NORMAL) != (lp.sched_priority == 0))
+ if ((policy == SCHED_NORMAL || policy == SCHED_ISO) != (lp.sched_priority == 0))
goto out_unlock;
retval = -EPERM;
@@ -1846,7 +1860,7 @@ static int setscheduler(pid_t pid, int p
p->policy = policy;
p->rt_priority = lp.sched_priority;
oldprio = p->prio;
- if (policy != SCHED_NORMAL)
+ if (policy == SCHED_FIFO || policy == SCHED_RR)
p->prio = MAX_USER_RT_PRIO-1 - p->rt_priority;
else
p->prio = p->static_prio;
@@ -2147,6 +2161,9 @@ asmlinkage long sys_sched_get_priority_m
case SCHED_NORMAL:
ret = 0;
break;
+ case SCHED_ISO:
+ ret = 0;
+ break;
}
return ret;
}
@@ -2169,6 +2186,8 @@ asmlinkage long sys_sched_get_priority_m
break;
case SCHED_NORMAL:
ret = 0;
+ case SCHED_ISO:
+ ret = 0;
}
return ret;
}
--Boundary-00=_ycpD/PyPw4utzLz--
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