thp: add debugfs handle to split all huge pages
Writing 1 into 'split_huge_pages' will try to find and split all huge
pages in the system. This is useful for debuging.
[akpm@linux-foundation.org: fix printk text, per Vlastimil]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index ab544b1..a0b910a 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -23,6 +23,7 @@
#include <linux/freezer.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
+#include <linux/debugfs.h>
#include <linux/migrate.h>
#include <linux/hashtable.h>
#include <linux/userfaultfd_k.h>
@@ -3350,3 +3351,61 @@
.scan_objects = deferred_split_scan,
.seeks = DEFAULT_SEEKS,
};
+
+#ifdef CONFIG_DEBUG_FS
+static int split_huge_pages_set(void *data, u64 val)
+{
+ struct zone *zone;
+ struct page *page;
+ unsigned long pfn, max_zone_pfn;
+ unsigned long total = 0, split = 0;
+
+ if (val != 1)
+ return -EINVAL;
+
+ for_each_populated_zone(zone) {
+ max_zone_pfn = zone_end_pfn(zone);
+ for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
+ if (!pfn_valid(pfn))
+ continue;
+
+ page = pfn_to_page(pfn);
+ if (!get_page_unless_zero(page))
+ continue;
+
+ if (zone != page_zone(page))
+ goto next;
+
+ if (!PageHead(page) || !PageAnon(page) ||
+ PageHuge(page))
+ goto next;
+
+ total++;
+ lock_page(page);
+ if (!split_huge_page(page))
+ split++;
+ unlock_page(page);
+next:
+ put_page(page);
+ }
+ }
+
+ pr_info("%lu of %lu THP split", split, total);
+
+ return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
+ "%llu\n");
+
+static int __init split_huge_pages_debugfs(void)
+{
+ void *ret;
+
+ ret = debugfs_create_file("split_huge_pages", 0644, NULL, NULL,
+ &split_huge_pages_fops);
+ if (!ret)
+ pr_warn("Failed to create split_huge_pages in debugfs");
+ return 0;
+}
+late_initcall(split_huge_pages_debugfs);
+#endif