Commit d7102e95 authored by akpm@osdl.org's avatar akpm@osdl.org Committed by Linus Torvalds
Browse files

[PATCH] sched: filter affine wakeups 



)

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

include/linux/sched.h

+4 −1
Original line number Diff line number Diff line
@@ -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;

kernel/sched.c

+9 −1
Original line number Diff line number Diff line
@@ -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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