hugetlb: derive huge pages nodes allowed from task mempolicy

This patch derives a "nodes_allowed" node mask from the numa mempolicy of
the task modifying the number of persistent huge pages to control the
allocation, freeing and adjusting of surplus huge pages when the pool page
count is modified via the new sysctl or sysfs attribute
"nr_hugepages_mempolicy".  The nodes_allowed mask is derived as follows:

* For "default" [NULL] task mempolicy, a NULL nodemask_t pointer
  is produced.  This will cause the hugetlb subsystem to use
  node_online_map as the "nodes_allowed".  This preserves the
  behavior before this patch.
* For "preferred" mempolicy, including explicit local allocation,
  a nodemask with the single preferred node will be produced.
  "local" policy will NOT track any internode migrations of the
  task adjusting nr_hugepages.
* For "bind" and "interleave" policy, the mempolicy's nodemask
  will be used.
* Other than to inform the construction of the nodes_allowed node
  mask, the actual mempolicy mode is ignored.  That is, all modes
  behave like interleave over the resulting nodes_allowed mask
  with no "fallback".

See the updated documentation [next patch] for more information
about the implications of this patch.

Examples:

Starting with:

	Node 0 HugePages_Total:     0
	Node 1 HugePages_Total:     0
	Node 2 HugePages_Total:     0
	Node 3 HugePages_Total:     0

Default behavior [with or without this patch] balances persistent
hugepage allocation across nodes [with sufficient contiguous memory]:

	sysctl vm.nr_hugepages[_mempolicy]=32

yields:

	Node 0 HugePages_Total:     8
	Node 1 HugePages_Total:     8
	Node 2 HugePages_Total:     8
	Node 3 HugePages_Total:     8

Of course, we only have nr_hugepages_mempolicy with the patch,
but with default mempolicy, nr_hugepages_mempolicy behaves the
same as nr_hugepages.

Applying mempolicy--e.g., with numactl [using '-m' a.k.a.
'--membind' because it allows multiple nodes to be specified
and it's easy to type]--we can allocate huge pages on
individual nodes or sets of nodes.  So, starting from the
condition above, with 8 huge pages per node, add 8 more to
node 2 using:

	numactl -m 2 sysctl vm.nr_hugepages_mempolicy=40

This yields:

	Node 0 HugePages_Total:     8
	Node 1 HugePages_Total:     8
	Node 2 HugePages_Total:    16
	Node 3 HugePages_Total:     8

The incremental 8 huge pages were restricted to node 2 by the
specified mempolicy.

Similarly, we can use mempolicy to free persistent huge pages
from specified nodes:

	numactl -m 0,1 sysctl vm.nr_hugepages_mempolicy=32

yields:

	Node 0 HugePages_Total:     4
	Node 1 HugePages_Total:     4
	Node 2 HugePages_Total:    16
	Node 3 HugePages_Total:     8

The 8 huge pages freed were balanced over nodes 0 and 1.

[rientjes@google.com: accomodate reworked NODEMASK_ALLOC]
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Andi Kleen <andi@firstfloor.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: Adam Litke <agl@us.ibm.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Eric Whitney <eric.whitney@hp.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 84 insertions, 13 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 324d1abae876..1125d818ea06 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1330,29 +1330,71 @@ static struct hstate *kobj_to_hstate(struct kobject *kobj)
         return NULL;
 }
 
-static ssize_t nr_hugepages_show(struct kobject *kobj,
+static ssize_t nr_hugepages_show_common(struct kobject *kobj,
                                         struct kobj_attribute *attr, char *buf)
 {
         struct hstate *h = kobj_to_hstate(kobj);
         return sprintf(buf, "%lu\n", h->nr_huge_pages);
 }
-static ssize_t nr_hugepages_store(struct kobject *kobj,
-                struct kobj_attribute *attr, const char *buf, size_t count)
+static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
+                        struct kobject *kobj, struct kobj_attribute *attr,
+                        const char *buf, size_t len)
 {
         int err;
-        unsigned long input;
+        unsigned long count;
         struct hstate *h = kobj_to_hstate(kobj);
+        NODEMASK_ALLOC(nodemask_t, nodes_allowed);
 
-        err = strict_strtoul(buf, 10, &input);
+        err = strict_strtoul(buf, 10, &count);
         if (err)
                 return 0;
 
-        h->max_huge_pages = set_max_huge_pages(h, input, &node_online_map);
+        if (!(obey_mempolicy && init_nodemask_of_mempolicy(nodes_allowed))) {
+                NODEMASK_FREE(nodes_allowed);
+                nodes_allowed = &node_online_map;
+        }
+        h->max_huge_pages = set_max_huge_pages(h, count, nodes_allowed);
 
-        return count;
+        if (nodes_allowed != &node_online_map)
+                NODEMASK_FREE(nodes_allowed);
+
+        return len;
+}
+
+static ssize_t nr_hugepages_show(struct kobject *kobj,
+                                       struct kobj_attribute *attr, char *buf)
+{
+        return nr_hugepages_show_common(kobj, attr, buf);
+}
+
+static ssize_t nr_hugepages_store(struct kobject *kobj,
+               struct kobj_attribute *attr, const char *buf, size_t len)
+{
+        return nr_hugepages_store_common(false, kobj, attr, buf, len);
 }
 HSTATE_ATTR(nr_hugepages);
 
+#ifdef CONFIG_NUMA
+
+/*
+ * hstate attribute for optionally mempolicy-based constraint on persistent
+ * huge page alloc/free.
+ */
+static ssize_t nr_hugepages_mempolicy_show(struct kobject *kobj,
+                                       struct kobj_attribute *attr, char *buf)
+{
+        return nr_hugepages_show_common(kobj, attr, buf);
+}
+
+static ssize_t nr_hugepages_mempolicy_store(struct kobject *kobj,
+               struct kobj_attribute *attr, const char *buf, size_t len)
+{
+        return nr_hugepages_store_common(true, kobj, attr, buf, len);
+}
+HSTATE_ATTR(nr_hugepages_mempolicy);
+#endif
+
+
 static ssize_t nr_overcommit_hugepages_show(struct kobject *kobj,
                                         struct kobj_attribute *attr, char *buf)
 {
@@ -1408,6 +1450,9 @@ static struct attribute *hstate_attrs[] = {
         &free_hugepages_attr.attr,
         &resv_hugepages_attr.attr,
         &surplus_hugepages_attr.attr,
+#ifdef CONFIG_NUMA
+        &nr_hugepages_mempolicy_attr.attr,
+#endif
         NULL,
 };
 
@@ -1574,9 +1619,9 @@ static unsigned int cpuset_mems_nr(unsigned int *array)
 }
 
 #ifdef CONFIG_SYSCTL
-int hugetlb_sysctl_handler(struct ctl_table *table, int write,
-                           void __user *buffer,
-                           size_t *length, loff_t *ppos)
+static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
+                         struct ctl_table *table, int write,
+                         void __user *buffer, size_t *length, loff_t *ppos)
 {
         struct hstate *h = &default_hstate;
         unsigned long tmp;
@@ -1588,13 +1633,39 @@ int hugetlb_sysctl_handler(struct ctl_table *table, int write,
         table->maxlen = sizeof(unsigned long);
         proc_doulongvec_minmax(table, write, buffer, length, ppos);
 
-        if (write)
-                h->max_huge_pages = set_max_huge_pages(h, tmp,
-                                                        &node_online_map);
+        if (write) {
+                NODEMASK_ALLOC(nodemask_t, nodes_allowed);
+                if (!(obey_mempolicy &&
+                               init_nodemask_of_mempolicy(nodes_allowed))) {
+                        NODEMASK_FREE(nodes_allowed);
+                        nodes_allowed = &node_states[N_HIGH_MEMORY];
+                }
+                h->max_huge_pages = set_max_huge_pages(h, tmp, nodes_allowed);
+
+                if (nodes_allowed != &node_states[N_HIGH_MEMORY])
+                        NODEMASK_FREE(nodes_allowed);
+        }
 
         return 0;
 }
 
+int hugetlb_sysctl_handler(struct ctl_table *table, int write,
+                          void __user *buffer, size_t *length, loff_t *ppos)
+{
+
+        return hugetlb_sysctl_handler_common(false, table, write,
+                                                        buffer, length, ppos);
+}
+
+#ifdef CONFIG_NUMA
+int hugetlb_mempolicy_sysctl_handler(struct ctl_table *table, int write,
+                          void __user *buffer, size_t *length, loff_t *ppos)
+{
+        return hugetlb_sysctl_handler_common(true, table, write,
+                                                        buffer, length, ppos);
+}
+#endif /* CONFIG_NUMA */
+
 int hugetlb_treat_movable_handler(struct ctl_table *table, int write,
                         void __user *buffer,
                         size_t *length, loff_t *ppos)