Commit d7102e95 authored by akpm@osdl.org's avatar akpm@osdl.org Committed by Linus Torvalds
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[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: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 198e2f18
......@@ -696,8 +696,11 @@ 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;
......
......@@ -1290,6 +1290,9 @@ static int try_to_wake_up(task_t *p, unsigned int state, int sync)
}
}
if (p->last_waker_cpu != this_cpu)
goto out_set_cpu;
if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
goto out_set_cpu;
......@@ -1360,6 +1363,8 @@ out_set_cpu:
cpu = task_cpu(p);
}
p->last_waker_cpu = this_cpu;
out_activate:
#endif /* CONFIG_SMP */
if (old_state == TASK_UNINTERRUPTIBLE) {
......@@ -1441,9 +1446,12 @@ void fastcall sched_fork(task_t *p, int clone_flags)
#ifdef CONFIG_SCHEDSTATS
memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
#if defined(CONFIG_SMP)
p->last_waker_cpu = cpu;
#if defined(__ARCH_WANT_UNLOCKED_CTXSW)
p->oncpu = 0;
#endif
#endif
#ifdef CONFIG_PREEMPT
/* Want to start with kernel preemption disabled. */
task_thread_info(p)->preempt_count = 1;
......
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