diff mbox series

[3/3] hugetlbfs: don't retry when pool page allocations start to fail

Message ID 20190802223930.30971-4-mike.kravetz@oracle.com (mailing list archive)
State New, archived
Headers show
Series address hugetlb page allocation stalls | expand

Commit Message

Mike Kravetz Aug. 2, 2019, 10:39 p.m. UTC 
When allocating hugetlbfs pool pages via /proc/sys/vm/nr_hugepages,
the pages will be interleaved between all nodes of the system.  If
nodes are not equal, it is quite possible for one node to fill up
before the others.  When this happens, the code still attempts to
allocate pages from the full node.  This results in calls to direct
reclaim and compaction which slow things down considerably.

When allocating pool pages, note the state of the previous allocation
for each node.  If previous allocation failed, do not use the
aggressive retry algorithm on successive attempts.  The allocation
will still succeed if there is memory available, but it will not try
as hard to free up memory.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 mm/hugetlb.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 76 insertions(+), 10 deletions(-)

Comments

Vlastimil Babka Aug. 5, 2019, 9:28 a.m. UTC | #1 
On 8/3/19 12:39 AM, Mike Kravetz wrote:
> When allocating hugetlbfs pool pages via /proc/sys/vm/nr_hugepages,
> the pages will be interleaved between all nodes of the system.  If
> nodes are not equal, it is quite possible for one node to fill up
> before the others.  When this happens, the code still attempts to
> allocate pages from the full node.  This results in calls to direct
> reclaim and compaction which slow things down considerably.
> 
> When allocating pool pages, note the state of the previous allocation
> for each node.  If previous allocation failed, do not use the
> aggressive retry algorithm on successive attempts.  The allocation
> will still succeed if there is memory available, but it will not try
> as hard to free up memory.
> 
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>

Looks like only part of the (agreed with) suggestions were implemented?
- set_max_huge_pages() returns -ENOMEM if nodemask can't be allocated,
but hugetlb_hstate_alloc_pages() doesn't.
- there's still __GFP_NORETRY in nodemask allocations
- (cosmetics) Mel pointed out that NODEMASK_FREE() works fine with NULL
pointers

Thanks,
Vlastimil
Mike Kravetz Aug. 5, 2019, 5:12 p.m. UTC | #2 
On 8/5/19 2:28 AM, Vlastimil Babka wrote:
> On 8/3/19 12:39 AM, Mike Kravetz wrote:
>> When allocating hugetlbfs pool pages via /proc/sys/vm/nr_hugepages,
>> the pages will be interleaved between all nodes of the system.  If
>> nodes are not equal, it is quite possible for one node to fill up
>> before the others.  When this happens, the code still attempts to
>> allocate pages from the full node.  This results in calls to direct
>> reclaim and compaction which slow things down considerably.
>>
>> When allocating pool pages, note the state of the previous allocation
>> for each node.  If previous allocation failed, do not use the
>> aggressive retry algorithm on successive attempts.  The allocation
>> will still succeed if there is memory available, but it will not try
>> as hard to free up memory.
>>
>> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> 
> Looks like only part of the (agreed with) suggestions were implemented?

My bad, I pulled in the wrong patch.

> - set_max_huge_pages() returns -ENOMEM if nodemask can't be allocated,
> but hugetlb_hstate_alloc_pages() doesn't.

That is somewhat intentional.  The calling context of the two routines is
significantly different.   hugetlb_hstate_alloc_pages is called at boot time
to handle command line parameters.  And, hugetlb_hstate_alloc_pages does not
return a value as it is of type void.

We 'could' print out a warning here.  But, if we can't allocate a node mask
I am pretty sure we will not be able to boot.  I will add a comment.

> - there's still __GFP_NORETRY in nodemask allocations
> - (cosmetics) Mel pointed out that NODEMASK_FREE() works fine with NULL
> pointers
diff mbox series

Patch

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ede7e7f5d1ab..c707207e208f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1405,12 +1405,25 @@  pgoff_t __basepage_index(struct page *page)
 }
 
 static struct page *alloc_buddy_huge_page(struct hstate *h,
-		gfp_t gfp_mask, int nid, nodemask_t *nmask)
+		gfp_t gfp_mask, int nid, nodemask_t *nmask,
+		nodemask_t *node_alloc_noretry)
 {
 	int order = huge_page_order(h);
 	struct page *page;
+	bool alloc_try_hard = true;
 
-	gfp_mask |= __GFP_COMP|__GFP_RETRY_MAYFAIL|__GFP_NOWARN;
+	/*
+	 * By default we always try hard to allocate the page with
+	 * __GFP_RETRY_MAYFAIL flag.  However, if we are allocating pages in
+	 * a loop (to adjust global huge page counts) and previous allocation
+	 * failed, do not continue to try hard on the same node.  Use the
+	 * node_alloc_noretry bitmap to manage this state information.
+	 */
+	if (node_alloc_noretry && node_isset(nid, *node_alloc_noretry))
+		alloc_try_hard = false;
+	gfp_mask |= __GFP_COMP|__GFP_NOWARN;
+	if (alloc_try_hard)
+		gfp_mask |= __GFP_RETRY_MAYFAIL;
 	if (nid == NUMA_NO_NODE)
 		nid = numa_mem_id();
 	page = __alloc_pages_nodemask(gfp_mask, order, nid, nmask);
@@ -1419,6 +1432,22 @@  static struct page *alloc_buddy_huge_page(struct hstate *h,
 	else
 		__count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
 
+	/*
+	 * If we did not specify __GFP_RETRY_MAYFAIL, but still got a page this
+	 * indicates an overall state change.  Clear bit so that we resume
+	 * normal 'try hard' allocations.
+	 */
+	if (node_alloc_noretry && page && !alloc_try_hard)
+		node_clear(nid, *node_alloc_noretry);
+
+	/*
+	 * If we tried hard to get a page but failed, set bit so that
+	 * subsequent attempts will not try as hard until there is an
+	 * overall state change.
+	 */
+	if (node_alloc_noretry && !page && alloc_try_hard)
+		node_set(nid, *node_alloc_noretry);
+
 	return page;
 }
 
@@ -1427,7 +1456,8 @@  static struct page *alloc_buddy_huge_page(struct hstate *h,
  * should use this function to get new hugetlb pages
  */
 static struct page *alloc_fresh_huge_page(struct hstate *h,
-		gfp_t gfp_mask, int nid, nodemask_t *nmask)
+		gfp_t gfp_mask, int nid, nodemask_t *nmask,
+		nodemask_t *node_alloc_noretry)
 {
 	struct page *page;
 
@@ -1435,7 +1465,7 @@  static struct page *alloc_fresh_huge_page(struct hstate *h,
 		page = alloc_gigantic_page(h, gfp_mask, nid, nmask);
 	else
 		page = alloc_buddy_huge_page(h, gfp_mask,
-				nid, nmask);
+				nid, nmask, node_alloc_noretry);
 	if (!page)
 		return NULL;
 
@@ -1450,14 +1480,16 @@  static struct page *alloc_fresh_huge_page(struct hstate *h,
  * Allocates a fresh page to the hugetlb allocator pool in the node interleaved
  * manner.
  */
-static int alloc_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed)
+static int alloc_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
+				nodemask_t *node_alloc_noretry)
 {
 	struct page *page;
 	int nr_nodes, node;
 	gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
 
 	for_each_node_mask_to_alloc(h, nr_nodes, node, nodes_allowed) {
-		page = alloc_fresh_huge_page(h, gfp_mask, node, nodes_allowed);
+		page = alloc_fresh_huge_page(h, gfp_mask, node, nodes_allowed,
+						node_alloc_noretry);
 		if (page)
 			break;
 	}
@@ -1601,7 +1633,7 @@  static struct page *alloc_surplus_huge_page(struct hstate *h, gfp_t gfp_mask,
 		goto out_unlock;
 	spin_unlock(&hugetlb_lock);
 
-	page = alloc_fresh_huge_page(h, gfp_mask, nid, nmask);
+	page = alloc_fresh_huge_page(h, gfp_mask, nid, nmask, NULL);
 	if (!page)
 		return NULL;
 
@@ -1637,7 +1669,7 @@  struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask,
 	if (hstate_is_gigantic(h))
 		return NULL;
 
-	page = alloc_fresh_huge_page(h, gfp_mask, nid, nmask);
+	page = alloc_fresh_huge_page(h, gfp_mask, nid, nmask, NULL);
 	if (!page)
 		return NULL;
 
@@ -2207,13 +2239,31 @@  static void __init gather_bootmem_prealloc(void)
 static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 {
 	unsigned long i;
+	nodemask_t *node_alloc_noretry;
+
+	if (!hstate_is_gigantic(h)) {
+		/*
+		 * bit mask controlling how hard we retry per-node
+		 * allocations.
+		 */
+		node_alloc_noretry = kmalloc(sizeof(*node_alloc_noretry),
+						GFP_KERNEL | __GFP_NORETRY);
+	} else {
+		/* allocations done at boot time */
+		node_alloc_noretry = NULL;
+	}
+
+	/* bit mask controlling how hard we retry per-node allocations */
+	if (node_alloc_noretry)
+		nodes_clear(*node_alloc_noretry);
 
 	for (i = 0; i < h->max_huge_pages; ++i) {
 		if (hstate_is_gigantic(h)) {
 			if (!alloc_bootmem_huge_page(h))
 				break;
 		} else if (!alloc_pool_huge_page(h,
-					 &node_states[N_MEMORY]))
+					 &node_states[N_MEMORY],
+					 node_alloc_noretry))
 			break;
 		cond_resched();
 	}
@@ -2225,6 +2275,8 @@  static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 			h->max_huge_pages, buf, i);
 		h->max_huge_pages = i;
 	}
+
+	kfree(node_alloc_noretry);
 }
 
 static void __init hugetlb_init_hstates(void)
@@ -2323,6 +2375,14 @@  static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
 			      nodemask_t *nodes_allowed)
 {
 	unsigned long min_count, ret;
+	NODEMASK_ALLOC(nodemask_t, node_alloc_noretry,
+						GFP_KERNEL | __GFP_NORETRY);
+
+	/* bit mask controlling how hard we retry per-node allocations */
+	if (node_alloc_noretry)
+		nodes_clear(*node_alloc_noretry);
+	else
+		return -ENOMEM;
 
 	spin_lock(&hugetlb_lock);
 
@@ -2356,6 +2416,8 @@  static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
 	if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) {
 		if (count > persistent_huge_pages(h)) {
 			spin_unlock(&hugetlb_lock);
+			if (node_alloc_noretry)
+				NODEMASK_FREE(node_alloc_noretry);
 			return -EINVAL;
 		}
 		/* Fall through to decrease pool */
@@ -2388,7 +2450,8 @@  static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
 		/* yield cpu to avoid soft lockup */
 		cond_resched();
 
-		ret = alloc_pool_huge_page(h, nodes_allowed);
+		ret = alloc_pool_huge_page(h, nodes_allowed,
+						node_alloc_noretry);
 		spin_lock(&hugetlb_lock);
 		if (!ret)
 			goto out;
@@ -2429,6 +2492,9 @@  static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
 	h->max_huge_pages = persistent_huge_pages(h);
 	spin_unlock(&hugetlb_lock);
 
+	if (node_alloc_noretry)
+		NODEMASK_FREE(node_alloc_noretry);
+
 	return 0;
 }