The patch titled
sched: rsdl check for niced tasks lowering prio level
has been added to the -mm tree. Its filename is
sched-rsdl-check-for-niced-tasks-lowering-prio-level.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: sched: rsdl check for niced tasks lowering prio level
From: Con Kolivas <kernel@xxxxxxxxxxx>
Ensure niced tasks are not inappropriately limiting sleeping unniced tasks
by explicitly checking what the best static priority that has run this
major rotation was.
Reimplement SCHED_BATCH using this check.
Signed-off-by: Con Kolivas <kernel@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sched.c | 33 ++++++++++++++++++++++++---------
1 file changed, 24 insertions(+), 9 deletions(-)
diff -puN kernel/sched.c~sched-rsdl-check-for-niced-tasks-lowering-prio-level kernel/sched.c
--- a/kernel/sched.c~sched-rsdl-check-for-niced-tasks-lowering-prio-level
+++ a/kernel/sched.c
@@ -201,8 +201,11 @@ struct rq {
struct prio_array *active, *expired, arrays[2];
unsigned long *dyn_bitmap, *exp_bitmap;
- int prio_level;
- /* The current dynamic priority level this runqueue is at */
+ int prio_level, best_static_prio;
+ /*
+ * The current dynamic priority level this runqueue is at, and the
+ * best static priority queued this major rotation.
+ */
unsigned long prio_rotation;
/* How many times we have rotated the priority queue */
@@ -704,16 +707,24 @@ static inline int entitled_slot(int stat
/*
* Find the first unused slot by this task that is also in its prio_matrix
- * level.
+ * level. Ensure that the prio_level is not unnecessarily low by checking
+ * that best_static_prio this major rotation was not a niced task.
+ * SCHED_BATCH tasks do not perform this check so they do not induce
+ * latencies in tasks of any nice level.
*/
static inline int next_entitled_slot(struct task_struct *p, struct rq *rq)
{
- DECLARE_BITMAP(tmp, PRIO_RANGE);
+ if (p->static_prio < rq->best_static_prio && p->policy != SCHED_BATCH)
+ return SCHED_PRIO(find_first_zero_bit(p->bitmap, PRIO_RANGE));
+ else {
+ DECLARE_BITMAP(tmp, PRIO_RANGE);
- bitmap_or(tmp, p->bitmap, prio_matrix[USER_PRIO(p->static_prio)],
- PRIO_RANGE);
- return SCHED_PRIO(find_next_zero_bit(tmp, PRIO_RANGE,
- USER_PRIO(rq->prio_level)));
+ bitmap_or(tmp, p->bitmap,
+ prio_matrix[USER_PRIO(p->static_prio)],
+ PRIO_RANGE);
+ return SCHED_PRIO(find_next_zero_bit(tmp, PRIO_RANGE,
+ USER_PRIO(rq->prio_level)));
+ }
}
static void queue_expired(struct task_struct *p, struct rq *rq)
@@ -3315,6 +3326,7 @@ static inline void major_prio_rotation(s
rq->active = new_array;
rq->exp_bitmap = rq->expired->prio_bitmap;
rq->dyn_bitmap = rq->active->prio_bitmap;
+ rq->best_static_prio = MAX_PRIO;
rq->prio_rotation++;
}
@@ -3640,10 +3652,12 @@ need_resched_nonpreemptible:
}
switch_tasks:
if (next == rq->idle) {
+ rq->best_static_prio = MAX_PRIO;
rq->prio_level = MAX_RT_PRIO;
rq->prio_rotation++;
schedstat_inc(rq, sched_goidle);
- }
+ } else if (next->static_prio < rq->best_static_prio)
+ rq->best_static_prio = next->static_prio;
prefetch(next);
prefetch_stack(next);
clear_tsk_need_resched(prev);
@@ -7093,6 +7107,7 @@ void __init sched_init(void)
lockdep_set_class(&rq->lock, &rq->rq_lock_key);
rq->nr_running = 0;
rq->prio_rotation = 0;
+ rq->best_static_prio = MAX_PRIO;
rq->prio_level = MAX_RT_PRIO;
rq->active = rq->arrays;
rq->expired = rq->arrays + 1;
_
Patches currently in -mm which might be from kernel@xxxxxxxxxxx are
sched-fix-idle-load-balancing-in-softirqd-context-fix.patch
sched-add-above-background-load-function.patch
mm-implement-swap-prefetching.patch
swap-prefetch-avoid-repeating-entry.patch
lists-add-list-splice-tail.patch
sched-remove-sleepavg-from-proc.patch
sched-remove-noninteractive-flag.patch
sched-dont-renice-kernel-threads.patch
sched-implement-rsdl-cpu-scheduler.patch
sched-document-rsdl-cpu-scheduler.patch
sched-rsdl-improvements.patch
sched-rsdl-check-for-niced-tasks-lowering-prio-level.patch
-
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