Re: [PATCH] sched: activate SCHED BATCH expired

Con Kolivas
2006-03-17T14:11:18Z

On Saturday 18 March 2006 00:46, Nick Piggin wrote:
> I guess it isn't doing the cmov because it doesn't want to do the
> extra load in the common case, which is fair enough (are you compiling
> for a pentiumpro+, without generic x86 support?

For pentium4 with no generic support.

> what about if you
> turn off optimise for size?)

Dunno, sleep is taking me...

> At least other archtectures might be able to make better use of it,
> and I agree even for i386 the code looks better (and slightly smaller).

Good enough for me. Here's a respin, thanks!

Cheers,
Con
---
To increase the strength of SCHED_BATCH as a scheduling hint we can activate
batch tasks on the expired array since by definition they are latency
insensitive tasks.

Signed-off-by: Con Kolivas <kernel@kolivas.org>

---
include/linux/sched.h | 1 +
kernel/sched.c | 10 +++++++---
2 files changed, 8 insertions(+), 3 deletions(-)

Index: linux-2.6.16-rc6-mm1/include/linux/sched.h
===================================================================
--- linux-2.6.16-rc6-mm1.orig/include/linux/sched.h 2006-03-13 20:12:22.000000000 +1100
+++ linux-2.6.16-rc6-mm1/include/linux/sched.h 2006-03-17 23:08:31.000000000 +1100
@@ -485,6 +485,7 @@ struct signal_struct {
#define MAX_PRIO (MAX_RT_PRIO + 40)

#define rt_task(p) (unlikely((p)->prio < MAX_RT_PRIO))
+#define batch_task(p) (unlikely((p)->policy == SCHED_BATCH))

/*
* Some day this will be a full-fledged user tracking system..
Index: linux-2.6.16-rc6-mm1/kernel/sched.c
===================================================================
--- linux-2.6.16-rc6-mm1.orig/kernel/sched.c 2006-03-13 20:12:15.000000000 +1100
+++ linux-2.6.16-rc6-mm1/kernel/sched.c 2006-03-18 01:05:02.000000000 +1100
@@ -737,9 +737,13 @@ static inline void dec_nr_running(task_t
/*
* __activate_task - move a task to the runqueue.
*/
-static inline void __activate_task(task_t *p, runqueue_t *rq)
+static void __activate_task(task_t *p, runqueue_t *rq)
{
- enqueue_task(p, rq->active);
+ prio_array_t *target = rq->active;
+
+ if (batch_task(p))
+ target = rq->expired;
+ enqueue_task(p, target);
inc_nr_running(p, rq);
}

@@ -758,7 +762,7 @@ static int recalc_task_prio(task_t *p, u
unsigned long long __sleep_time = now - p->timestamp;
unsigned long sleep_time;

- if (unlikely(p->policy == SCHED_BATCH))
+ if (batch_task(p))
sleep_time = 0;
else {
if (__sleep_time > NS_MAX_SLEEP_AVG)