Lee Schermerhorn
2009-09-09T16:31:39Z

[PATCH 2/6] hugetlb: add nodemask arg to huge page alloc, free and surplus adjust fcns

Against: 2.6.31-rc7-mmotm-090827-1651

V3: + moved this patch to after the "rework" of hstate_next_node_to_...
functions as this patch is more specific to using task mempolicy
to control huge page allocation and freeing.

V5: + removed now unneeded 'nextnid' from hstate_next_node_to_{alloc|free}
and updated the stale comments.

V6: + move defaulting of nodes_allowed [to &node_online_map] up to
set_max_huge_pages(). Eliminate from hstate_next_node_*()
functions. [David Rientjes' suggestion].
+ renamed "this_node_allowed()" to "get_valid_node_allowed()"
[for David]

In preparation for constraining huge page allocation and freeing by the
controlling task's numa mempolicy, add a "nodes_allowed" nodemask pointer
to the allocate, free and surplus adjustment functions. For now, pass
NULL to indicate default behavior--i.e., use node_online_map. A
subsqeuent patch will derive a non-default mask from the controlling
task's numa mempolicy.

Note that this method of updating the global hstate nr_hugepages under
the constraint of a nodemask simplifies keeping the global state
consistent--especially the number of persistent and surplus pages
relative to reservations and overcommit limits. There are undoubtedly
other ways to do this, but this works for both interfaces: mempolicy
and per node attributes.

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Reviewed-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: David Rientjes <rientjes@google.com>

mm/hugetlb.c | 120 ++++++++++++++++++++++++++++++++++-------------------------
1 file changed, 71 insertions(+), 49 deletions(-)

Index: linux-2.6.31-rc7-mmotm-090827-1651/mm/hugetlb.c
===================================================================
--- linux-2.6.31-rc7-mmotm-090827-1651.orig/mm/hugetlb.c 2009-09-09 11:57:34.000000000 -0400
+++ linux-2.6.31-rc7-mmotm-090827-1651/mm/hugetlb.c 2009-09-09 11:57:34.000000000 -0400
@@ -622,48 +622,56 @@ static struct page *alloc_fresh_huge_pag
}

/*
- * common helper function for hstate_next_node_to_{alloc|free}.
- * return next node in node_online_map, wrapping at end.
+ * common helper functions for hstate_next_node_to_{alloc|free}.
+ * We may have allocated or freed a huge page based on a different
+ * nodes_allowed previously, so h->next_node_to_{alloc|free} might
+ * be outside of *nodes_allowed. Ensure that we use an allowed
+ * node for alloc or free.
*/
-static int next_node_allowed(int nid)
+static int next_node_allowed(int nid, nodemask_t *nodes_allowed)
{
- nid = next_node(nid, node_online_map);
+ nid = next_node(nid, *nodes_allowed);
if (nid == MAX_NUMNODES)
- nid = first_node(node_online_map);
+ nid = first_node(*nodes_allowed);
VM_BUG_ON(nid >= MAX_NUMNODES);

return nid;
}

+static int get_valid_node_allowed(int nid, nodemask_t *nodes_allowed)
+{
+ if (!node_isset(nid, *nodes_allowed))
+ nid = next_node_allowed(nid, nodes_allowed);
+ return nid;
+}
+
/*
- * Use a helper variable to find the next node and then
- * copy it back to next_nid_to_alloc afterwards:
- * otherwise there's a window in which a racer might
- * pass invalid nid MAX_NUMNODES to alloc_pages_exact_node.
- * But we don't need to use a spin_lock here: it really
- * doesn't matter if occasionally a racer chooses the
- * same nid as we do. Move nid forward in the mask even
- * if we just successfully allocated a hugepage so that
- * the next caller gets hugepages on the next node.
+ * returns the previously saved node ["this node"] from which to
+ * allocate a persistent huge page for the pool and advance the
+ * next node from which to allocate, handling wrap at end of node
+ * mask.
*/
-static int hstate_next_node_to_alloc(struct hstate *h)
+static int hstate_next_node_to_alloc(struct hstate *h,
+ nodemask_t *nodes_allowed)
{
- int nid, next_nid;
+ int nid;
+
+ VM_BUG_ON(!nodes_allowed);
+
+ nid = get_valid_node_allowed(h->next_nid_to_alloc, nodes_allowed);
+ h->next_nid_to_alloc = next_node_allowed(nid, nodes_allowed);

- nid = h->next_nid_to_alloc;
- next_nid = next_node_allowed(nid);
- h->next_nid_to_alloc = next_nid;
return nid;
}

-static int alloc_fresh_huge_page(struct hstate *h)
+static int alloc_fresh_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
{
struct page *page;
int start_nid;
int next_nid;
int ret = 0;

- start_nid = hstate_next_node_to_alloc(h);
+ start_nid = hstate_next_node_to_alloc(h, nodes_allowed);
next_nid = start_nid;

do {
@@ -672,7 +680,7 @@ static int alloc_fresh_huge_page(struct
ret = 1;
break;
}
- next_nid = hstate_next_node_to_alloc(h);
+ next_nid = hstate_next_node_to_alloc(h, nodes_allowed);
} while (next_nid != start_nid);

if (ret)
@@ -684,18 +692,20 @@ static int alloc_fresh_huge_page(struct
}

/*
- * helper for free_pool_huge_page() - return the next node
- * from which to free a huge page. Advance the next node id
- * whether or not we find a free huge page to free so that the
- * next attempt to free addresses the next node.
+ * helper for free_pool_huge_page() - return the previously saved
+ * node ["this node"] from which to free a huge page. Advance the
+ * next node id whether or not we find a free huge page to free so
+ * that the next attempt to free addresses the next node.
*/
-static int hstate_next_node_to_free(struct hstate *h)
+static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
{
- int nid, next_nid;
+ int nid;
+
+ VM_BUG_ON(!nodes_allowed);
+
+ nid = get_valid_node_allowed(h->next_nid_to_free, nodes_allowed);
+ h->next_nid_to_free = next_node_allowed(nid, nodes_allowed);

- nid = h->next_nid_to_free;
- next_nid = next_node_allowed(nid);
- h->next_nid_to_free = next_nid;
return nid;
}

@@ -705,13 +715,14 @@ static int hstate_next_node_to_free(stru
* balanced over allowed nodes.
* Called with hugetlb_lock locked.
*/
-static int free_pool_huge_page(struct hstate *h, bool acct_surplus)
+static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
+ bool acct_surplus)
{
int start_nid;
int next_nid;
int ret = 0;

- start_nid = hstate_next_node_to_free(h);
+ start_nid = hstate_next_node_to_free(h, nodes_allowed);
next_nid = start_nid;

do {
@@ -735,7 +746,7 @@ static int free_pool_huge_page(struct hs
ret = 1;
break;
}
- next_nid = hstate_next_node_to_free(h);
+ next_nid = hstate_next_node_to_free(h, nodes_allowed);
} while (next_nid != start_nid);

return ret;
@@ -937,7 +948,7 @@ static void return_unused_surplus_pages(
* on-line nodes for us and will handle the hstate accounting.
*/
while (nr_pages--) {
- if (!free_pool_huge_page(h, 1))
+ if (!free_pool_huge_page(h, &node_online_map, 1))
break;
}
}
@@ -1047,7 +1058,7 @@ int __weak alloc_bootmem_huge_page(struc
void *addr;

addr = __alloc_bootmem_node_nopanic(
- NODE_DATA(hstate_next_node_to_alloc(h)),
+ NODE_DATA(hstate_next_node_to_alloc(h, NULL)),
huge_page_size(h), huge_page_size(h), 0);

if (addr) {
@@ -1102,7 +1113,7 @@ static void __init hugetlb_hstate_alloc_
if (h->order >= MAX_ORDER) {
if (!alloc_bootmem_huge_page(h))
break;
- } else if (!alloc_fresh_huge_page(h))
+ } else if (!alloc_fresh_huge_page(h, &node_online_map))
break;
}
h->max_huge_pages = i;
@@ -1144,16 +1155,22 @@ static void __init report_hugepages(void
}

#ifdef CONFIG_HIGHMEM
-static void try_to_free_low(struct hstate *h, unsigned long count)
+static void try_to_free_low(struct hstate *h, unsigned long count,
+ nodemask_t *nodes_allowed)
{
int i;

if (h->order >= MAX_ORDER)
return;

+ if (!nodes_allowed)
+ nodes_allowed = &node_online_map;
+
for (i = 0; i < MAX_NUMNODES; ++i) {
struct page *page, *next;
struct list_head *freel = &h->hugepage_freelists[i];
+ if (!node_isset(i, *nodes_allowed))
+ continue;
list_for_each_entry_safe(page, next, freel, lru) {
if (count >= h->nr_huge_pages)
return;
@@ -1167,7 +1184,8 @@ static void try_to_free_low(struct hstat
}
}
#else
-static inline void try_to_free_low(struct hstate *h, unsigned long count)
+static inline void try_to_free_low(struct hstate *h, unsigned long count,
+ nodemask_t *nodes_allowed)
{
}
#endif
@@ -1177,7 +1195,8 @@ static inline void try_to_free_low(struc
* balanced by operating on them in a round-robin fashion.
* Returns 1 if an adjustment was made.
*/
-static int adjust_pool_surplus(struct hstate *h, int delta)
+static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
+ int delta)
{
int start_nid, next_nid;
int ret = 0;
@@ -1185,9 +1204,9 @@ static int adjust_pool_surplus(struct hs
VM_BUG_ON(delta != -1 && delta != 1);

if (delta < 0)
- start_nid = hstate_next_node_to_alloc(h);
+ start_nid = hstate_next_node_to_alloc(h, nodes_allowed);
else
- start_nid = hstate_next_node_to_free(h);
+ start_nid = hstate_next_node_to_free(h, nodes_allowed);
next_nid = start_nid;

do {
@@ -1197,7 +1216,8 @@ static int adjust_pool_surplus(struct hs
* To shrink on this node, there must be a surplus page
*/
if (!h->surplus_huge_pages_node[nid]) {
- next_nid = hstate_next_node_to_alloc(h);
+ next_nid = hstate_next_node_to_alloc(h,
+ nodes_allowed);
continue;
}
}
@@ -1207,7 +1227,8 @@ static int adjust_pool_surplus(struct hs
*/
if (h->surplus_huge_pages_node[nid] >=
h->nr_huge_pages_node[nid]) {
- next_nid = hstate_next_node_to_free(h);
+ next_nid = hstate_next_node_to_free(h,
+ nodes_allowed);
continue;
}
}
@@ -1225,6 +1246,7 @@ static int adjust_pool_surplus(struct hs
static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count)
{
unsigned long min_count, ret;
+ nodemask_t *nodes_allowed = &node_online_map;

if (h->order >= MAX_ORDER)
return h->max_huge_pages;
@@ -1242,7 +1264,7 @@ static unsigned long set_max_huge_pages(
*/
spin_lock(&hugetlb_lock);
while (h->surplus_huge_pages && count > persistent_huge_pages(h)) {
- if (!adjust_pool_surplus(h, -1))
+ if (!adjust_pool_surplus(h, nodes_allowed, -1))
break;
}

@@ -1253,7 +1275,7 @@ static unsigned long set_max_huge_pages(
* and reducing the surplus.
*/
spin_unlock(&hugetlb_lock);
- ret = alloc_fresh_huge_page(h);
+ ret = alloc_fresh_huge_page(h, nodes_allowed);
spin_lock(&hugetlb_lock);
if (!ret)
goto out;
@@ -1277,13 +1299,13 @@ static unsigned long set_max_huge_pages(
*/
min_count = h->resv_huge_pages + h->nr_huge_pages - h->free_huge_pages;
min_count = max(count, min_count);
- try_to_free_low(h, min_count);
+ try_to_free_low(h, min_count, nodes_allowed);
while (min_count < persistent_huge_pages(h)) {
- if (!free_pool_huge_page(h, 0))
+ if (!free_pool_huge_page(h, nodes_allowed, 0))
break;
}
while (count < persistent_huge_pages(h)) {
- if (!adjust_pool_surplus(h, 1))
+ if (!adjust_pool_surplus(h, nodes_allowed, 1))
break;
}
out:

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