Add another layer of fallback policy to make the home node concept
useful from a memory allocation PoV.
This changes the mpol order to:
- vma->vm_ops->get_policy [if applicable]
- vma->vm_policy [if applicable]
- task->mempolicy
- tsk_home_node() preferred [NEW]
- default_policy
Note that the tsk_home_node() policy has Migrate-on-Fault enabled to
facilitate efficient on-demand memory migration.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
mm/mempolicy.c | 29 +++++++++++++++++++++++++++--
1 file changed, 27 insertions(+), 2 deletions(-)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -117,6 +117,22 @@ 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 = tsk_home_node(p);
+ if (node != -1)
+ pol = &preferred_node_policy[node];
+ }
+
+ return pol;
+}
+
static const struct mempolicy_operations {
int (*create)(struct mempolicy *pol, const nodemask_t *nodes);
/*
@@ -1478,7 +1494,7 @@ asmlinkage long compat_sys_mbind(compat_
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) {
@@ -1856,7 +1872,7 @@ alloc_pages_vma(gfp_t gfp, int order, st
*/
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;
if (!pol || in_interrupt() || (gfp & __GFP_THISNODE))
@@ -2302,6 +2318,15 @@ 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,
+ .v = { .preferred_node = nid, },
+ };
+ }
+
/*
* Set interleaving policy for system init. Interleaving is only
* enabled across suitably sized nodes (default is >= 16MB), or
--
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