Commit 2d4056fa authored by Srikar Dronamraju's avatar Srikar Dronamraju Committed by Ingo Molnar
Browse files

sched/numa: Remove numa_has_capacity() 



task_numa_find_cpu() helps to find the CPU to swap/move the task to.
It's guarded by numa_has_capacity(). However node not having capacity
shouldn't deter a task swapping if it helps NUMA placement.

Further load_too_imbalanced(), which evaluates possibilities of move/swap,
provides similar checks as numa_has_capacity.

Hence remove numa_has_capacity() to enhance possibilities of task
swapping even if load is imbalanced.

Running SPECjbb2005 on a 4 node machine and comparing bops/JVM
JVMS  LAST_PATCH  WITH_PATCH  %CHANGE
16    25657.9     25804.1     0.569
1     74435       73413       -1.37

Signed-off-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarRik van Riel <riel@surriel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1529514181-9842-13-git-send-email-srikar@linux.vnet.ibm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 0ad4e3df

kernel/sched/fair.c

+3 −33
Original line number Diff line number Diff line
@@ -1456,7 +1456,6 @@ struct numa_stats { 
	unsigned long compute_capacity;



	unsigned int nr_running;

	int has_free_capacity;

};



/*
@@ -1483,8 +1482,7 @@ static void update_numa_stats(struct numa_stats *ns, int nid) 
	 * the @ns structure is NULL'ed and task_numa_compare() will

	 * not find this node attractive.

	 *

	 * We'll either bail at !has_free_capacity, or we'll detect a huge

	 * imbalance and bail there.

	 * We'll detect a huge imbalance and bail there.

	 */

	if (!cpus)

		return;
@@ -1495,7 +1493,6 @@ static void update_numa_stats(struct numa_stats *ns, int nid) 


	capacity = min_t(unsigned, capacity,

		DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));

	ns->has_free_capacity = (ns->nr_running < capacity);

}



struct task_numa_env {
@@ -1698,31 +1695,6 @@ static void task_numa_find_cpu(struct task_numa_env *env, 
	}

}



/* Only move tasks to a NUMA node less busy than the current node. */

static bool numa_has_capacity(struct task_numa_env *env)

{

	struct numa_stats *src = &env->src_stats;

	struct numa_stats *dst = &env->dst_stats;



	if (src->has_free_capacity && !dst->has_free_capacity)

		return false;



	/*

	 * Only consider a task move if the source has a higher load

	 * than the destination, corrected for CPU capacity on each node.

	 *

	 *      src->load                dst->load

	 * --------------------- vs ---------------------

	 * src->compute_capacity    dst->compute_capacity

	 */

	if (src->load * dst->compute_capacity * env->imbalance_pct >



	    dst->load * src->compute_capacity * 100)

		return true;



	return false;

}



static int task_numa_migrate(struct task_struct *p)

{

	struct task_numa_env env = {
@@ -1777,7 +1749,6 @@ static int task_numa_migrate(struct task_struct *p) 
	update_numa_stats(&env.dst_stats, env.dst_nid);



	/* Try to find a spot on the preferred nid. */

	if (numa_has_capacity(&env))

	task_numa_find_cpu(&env, taskimp, groupimp);



	/*
@@ -1808,7 +1779,6 @@ static int task_numa_migrate(struct task_struct *p) 
			env.dist = dist;

			env.dst_nid = nid;

			update_numa_stats(&env.dst_stats, env.dst_nid);

			if (numa_has_capacity(&env))

			task_numa_find_cpu(&env, taskimp, groupimp);

		}

	}

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