mm, page_owner: convert page_owner_inited to static key

CONFIG_PAGE_OWNER attempts to impose negligible runtime overhead when
enabled during compilation, but not actually enabled during runtime by
boot param page_owner=on.  This overhead can be further reduced using
the static key mechanism, which this patch does.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 6 insertions, 5 deletions

diff --git a/mm/page_owner.c b/mm/page_owner.c
index 7a37a30d941b..feaa28b40c1c 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -5,10 +5,11 @@
 #include <linux/bootmem.h>
 #include <linux/stacktrace.h>
 #include <linux/page_owner.h>
+#include <linux/jump_label.h>
 #include "internal.h"
 
 static bool page_owner_disabled = true;
-bool page_owner_inited __read_mostly;
+DEFINE_STATIC_KEY_FALSE(page_owner_inited);
 
 static void init_early_allocated_pages(void);
 
@@ -37,7 +38,7 @@ static void init_page_owner(void)
         if (page_owner_disabled)
                 return;
 
-        page_owner_inited = true;
+        static_branch_enable(&page_owner_inited);
         init_early_allocated_pages();
 }
 
@@ -147,7 +148,7 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
         struct page *page;
         struct page_ext *page_ext;
 
-        if (!page_owner_inited)
+        if (!static_branch_unlikely(&page_owner_inited))
                 return -EINVAL;
 
         page = NULL;
@@ -295,7 +296,7 @@ static int __init pageowner_init(void)
 {
         struct dentry *dentry;
 
-        if (!page_owner_inited) {
+        if (!static_branch_unlikely(&page_owner_inited)) {
                 pr_info("page_owner is disabled\n");
                 return 0;
         }
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 72c17981cb70..69ce64f7b8d7 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1120,7 +1120,7 @@ static void pagetypeinfo_showmixedcount(struct seq_file *m, pg_data_t *pgdat)
 #ifdef CONFIG_PAGE_OWNER
         int mtype;
 
-        if (!page_owner_inited)
+        if (!static_branch_unlikely(&page_owner_inited))
                 return;
 
         drain_all_pages(NULL);