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authorNick Piggin <nickpiggin@yahoo.com.au>2005-06-25 14:57:30 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-25 16:24:44 -0700
commit77391d71681d05d2f4502f91ad62618522abf624 (patch)
treee8931edb38a4ef3b7eb9e5ec7d25f7128e049994 /kernel
parent476d139c218e44e045e4bc6d4cc02b010b343939 (diff)
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[PATCH] sched: relax pinned balancing
The maximum rebalance interval allowed by the multiprocessor balancing backoff is often not large enough to handle corner cases where there are lots of tasks pinned on a CPU. Suresh reported: I see system livelock's if for example I have 7000 processes pinned onto one cpu (this is on the fastest 8-way system I have access to). After this patch, the machine is reported to go well above this number. Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 579da278e72..6e452eb95ac 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2031,6 +2031,12 @@ static runqueue_t *find_busiest_queue(struct sched_group *group)
}
/*
+ * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
+ * so long as it is large enough.
+ */
+#define MAX_PINNED_INTERVAL 512
+
+/*
* Check this_cpu to ensure it is balanced within domain. Attempt to move
* tasks if there is an imbalance.
*
@@ -2042,7 +2048,7 @@ static int load_balance(int this_cpu, runqueue_t *this_rq,
struct sched_group *group;
runqueue_t *busiest;
unsigned long imbalance;
- int nr_moved, all_pinned;
+ int nr_moved, all_pinned = 0;
int active_balance = 0;
spin_lock(&this_rq->lock);
@@ -2133,7 +2139,8 @@ out_balanced:
sd->nr_balance_failed = 0;
/* tune up the balancing interval */
- if (sd->balance_interval < sd->max_interval)
+ if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
+ (sd->balance_interval < sd->max_interval))
sd->balance_interval *= 2;
return 0;