When a system runs out of memory it may be desirable to reclaim
unreserved hugepages. This situation arises when a correctly configured
system has a memory failure and takes corrective action of rebooting and
removing the memory from the memory pool results in a system failing to
boot. With this change, the out of memory handler is able to reclaim
any pages that are free and not reserved.
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
---
include/linux/hugetlb.h | 1 +
mm/hugetlb.c | 35 +++++++++++++++++++++++++++++++++++
mm/oom_kill.c | 8 ++++++++
3 files changed, 44 insertions(+)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 8d9fe131a240..20e5729b9e9a 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -470,6 +470,7 @@ static inline pgoff_t basepage_index(struct page *page)
}
extern int dissolve_free_huge_page(struct page *page);
+extern unsigned long decrease_free_hugepages(nodemask_t *nodes);
extern int dissolve_free_huge_pages(unsigned long start_pfn,
unsigned long end_pfn);
static inline bool hugepage_migration_supported(struct hstate *h)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index bc48ee783dd9..00a0e08b96c5 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1454,6 +1454,41 @@ static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed,
}
/*
+ * Decrement free hugepages. Used by oom kill to avoid killing a task if
+ * there is free huge pages that can be used instead.
+ * Returns the number of bytes reclaimed from hugepages
+ */
+#define CONFIG_HUGETLB_PAGE_OOM
+unsigned long decrease_free_hugepages(nodemask_t *nodes)
+{
+#ifdef CONFIG_HUGETLB_PAGE_OOM
+ struct hstate *h;
+ unsigned long ret = 0;
+
+ spin_lock(&hugetlb_lock);
+ for_each_hstate(h) {
+ if (h->free_huge_pages > h->resv_huge_pages) {
+ char buf[32];
+
+ memfmt(buf, huge_page_size(h));
+ ret = free_pool_huge_page(h, nodes ?
+ nodes : &node_online_map, 0);
+ pr_warn("HugeTLB: Reclaiming %lu hugepage(s) of page size %s\n",
+ ret, buf);
+ ret *= huge_page_size(h);
+ goto found;
+ }
+ }
+
+found:
+ spin_unlock(&hugetlb_lock);
+ return ret;
+#else
+ return 0;
+#endif /* CONFIG_HUGETLB_PAGE_OOM */
+}
+
+/*
* Dissolve a given free hugepage into free buddy pages. This function does
* nothing for in-use (including surplus) hugepages. Returns -EBUSY if the
* number of free hugepages would be reduced below the number of reserved
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 9e8b4f030c1c..0a42f6d7d253 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -40,6 +40,7 @@
#include <linux/ratelimit.h>
#include <linux/kthread.h>
#include <linux/init.h>
+#include <linux/hugetlb.h>
#include <asm/tlb.h>
#include "internal.h"
@@ -1044,6 +1045,13 @@ bool out_of_memory(struct oom_control *oc)
return true;
}
+ /* Reclaim a free, unreserved hugepage. */
+ freed = decrease_free_hugepages(oc->nodemask);
+ if (freed != 0) {
+ pr_err("Out of memory: Reclaimed %lu from HugeTLB\n", freed);
+ return true;
+ }
+
select_bad_process(oc);
/* Found nothing?!?! Either we hang forever, or we panic. */
if (!oc->chosen && !is_sysrq_oom(oc) && !is_memcg_oom(oc)) {
--
2.13.0.90.g1eb437020
--
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