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Commit 5606e387 authored by Mel Gorman's avatar Mel Gorman
Browse files

mm: numa: Migrate on reference policy 



This is the simplest possible policy that still does something of note.
When a pte_numa is faulted, it is moved immediately. Any replacement
policy must at least do better than this and in all likelihood this
policy regresses normal workloads.

Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
Acked-by: default avatarRik van Riel <riel@redhat.com>
parent 03c5a6e1

include/uapi/linux/mempolicy.h

+1 −0
Original line number Diff line number Diff line
@@ -67,6 +67,7 @@ enum mpol_rebind_step { 
#define MPOL_F_LOCAL   (1 << 1)	/* preferred local allocation */

#define MPOL_F_REBINDING (1 << 2)	/* identify policies in rebinding */

#define MPOL_F_MOF	(1 << 3) /* this policy wants migrate on fault */

#define MPOL_F_MORON	(1 << 4) /* Migrate On pte_numa Reference On Node */





#endif /* _UAPI_LINUX_MEMPOLICY_H */

mm/mempolicy.c

+36 −2
Original line number Diff line number Diff line
@@ -118,6 +118,26 @@ static struct mempolicy default_policy = { 
	.flags = MPOL_F_LOCAL,

};



static struct mempolicy preferred_node_policy[MAX_NUMNODES];



static struct mempolicy *get_task_policy(struct task_struct *p)

{

	struct mempolicy *pol = p->mempolicy;

	int node;



	if (!pol) {

		node = numa_node_id();

		if (node != -1)

			pol = &preferred_node_policy[node];



		/* preferred_node_policy is not initialised early in boot */

		if (!pol->mode)

			pol = NULL;

	}



	return pol;

}



static const struct mempolicy_operations {

	int (*create)(struct mempolicy *pol, const nodemask_t *nodes);

	/*
@@ -1598,7 +1618,7 @@ asmlinkage long compat_sys_mbind(compat_ulong_t start, compat_ulong_t len, 
struct mempolicy *get_vma_policy(struct task_struct *task,

		struct vm_area_struct *vma, unsigned long addr)

{

	struct mempolicy *pol = task->mempolicy;

	struct mempolicy *pol = get_task_policy(task);



	if (vma) {

		if (vma->vm_ops && vma->vm_ops->get_policy) {
@@ -2021,7 +2041,7 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma, 
 */

struct page *alloc_pages_current(gfp_t gfp, unsigned order)

{

	struct mempolicy *pol = current->mempolicy;

	struct mempolicy *pol = get_task_policy(current);

	struct page *page;

	unsigned int cpuset_mems_cookie;
@@ -2295,6 +2315,11 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long 
	default:

		BUG();

	}



	/* Migrate the page towards the node whose CPU is referencing it */

	if (pol->flags & MPOL_F_MORON)

		polnid = numa_node_id();



	if (curnid != polnid)

		ret = polnid;

out:
@@ -2483,6 +2508,15 @@ void __init numa_policy_init(void) 
				     sizeof(struct sp_node),

				     0, SLAB_PANIC, NULL);



	for_each_node(nid) {

		preferred_node_policy[nid] = (struct mempolicy) {

			.refcnt = ATOMIC_INIT(1),

			.mode = MPOL_PREFERRED,

			.flags = MPOL_F_MOF | MPOL_F_MORON,

			.v = { .preferred_node = nid, },

		};

	}



	/*

	 * Set interleaving policy for system init. Interleaving is only

	 * enabled across suitably sized nodes (default is >= 16MB), or