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| author | Nick Piggin <nickpiggin@yahoo.com.au> | 2005-06-25 14:57:30 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-06-25 16:24:44 -0700 |
| commit | 77391d71681d05d2f4502f91ad62618522abf624 (patch) | |
| tree | e8931edb38a4ef3b7eb9e5ec7d25f7128e049994 /kernel/sched.c | |
| parent | 476d139c218e44e045e4bc6d4cc02b010b343939 (diff) | |
| download | lwn-77391d71681d05d2f4502f91ad62618522abf624.tar.gz lwn-77391d71681d05d2f4502f91ad62618522abf624.zip | |
[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/sched.c')
| -rw-r--r-- | kernel/sched.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index 579da278e72f..6e452eb95ac3 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; |