[PATCH] sched: filter affine wakeups

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From: Nick Piggin <nickpiggin@yahoo.com.au>

Track the last waker CPU, and only consider wakeup-balancing if there's a
match between current waker CPU and the previous waker CPU.  This ensures
that there is some correlation between two subsequent wakeup events before
we move the task.  Should help random-wakeup workloads on large SMP
systems, by reducing the migration attempts by a factor of nr_cpus.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5d6b9228bba9..b5ef92a043a6 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -696,9 +696,12 @@ struct task_struct {
 
         int lock_depth;         /* BKL lock depth */
 
-#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
+#if defined(CONFIG_SMP)
+        int last_waker_cpu;     /* CPU that last woke this task up */
+#if defined(__ARCH_WANT_UNLOCKED_CTXSW)
         int oncpu;
 #endif
+#endif
         int prio, static_prio;
         struct list_head run_list;
         prio_array_t *array;