Re: [PATCH] sched: Add SCHED_BGND (background) scheduling policy

From: Peter Williams
Date: Wed Jul 05 2006 - 04:02:33 EST


Ingo Molnar wrote:
* Peter Williams <pwil3058@xxxxxxxxxxxxxx> wrote:

===================================================================
--- MM-2.6.17-mm6.orig/kernel/mutex.c 2006-07-04 14:37:43.000000000 +1000
+++ MM-2.6.17-mm6/kernel/mutex.c 2006-07-04 14:38:12.000000000 +1000
@@ -51,6 +51,16 @@ __mutex_init(struct mutex *lock, const c
EXPORT_SYMBOL(__mutex_init);
+static inline void inc_mutex_count(void)
+{
+ current->mutexes_held++;
+}
+
+static inline void dec_mutex_count(void)
+{
+ current->mutexes_held--;
+}
+

NACK! This whole patch is way too intrusive for such a relatively small gain.

also, if something doesnt hold a mutex, it might still be unsafe to background it! For example if it holds a semaphore. Or an rwsem. Or any other kernel resource that has exclusion semantics.

so unless this patch gets _much_ less complex and much less intrusive, we'll have to stay with SCHED_BATCH and nice +19.

This means being less strict but (as you imply) that may be not much better than nice +19. I'll have a look at it.

Of course, a comprehensive (as opposed to RT only) priority inheritance mechanism would make the "safe/unsafe to background" problem go away and make this patch very simple. Any plans in that direction?

Peter
--
Peter Williams pwil3058@xxxxxxxxxxxxxx

"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/