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[PATCH v2 3/9] mm, page_owner: convert page_owner_inited to static key

From Vlastimil Babka <vbabka@suse.cz>
Newsgroups linux.kernel
Subject [PATCH v2 3/9] mm, page_owner: convert page_owner_inited to static key
Date 2015-11-24 13:40 +0100
Message-ID <qyl35-86O-35@gated-at.bofh.it> (permalink)
References <qyl33-86O-5@gated-at.bofh.it>
Organization linux.* mail to news gateway

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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>
---
 Documentation/vm/page_owner.txt |  9 +++++----
 include/linux/page_owner.h      | 22 ++++++++++------------
 mm/page_owner.c                 |  9 +++++----
 mm/vmstat.c                     |  2 +-
 4 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/Documentation/vm/page_owner.txt b/Documentation/vm/page_owner.txt
index 8f3ce9b..ffff143 100644
--- a/Documentation/vm/page_owner.txt
+++ b/Documentation/vm/page_owner.txt
@@ -28,10 +28,11 @@ with page owner and page owner is disabled in runtime due to no enabling
 boot option, runtime overhead is marginal. If disabled in runtime, it
 doesn't require memory to store owner information, so there is no runtime
 memory overhead. And, page owner inserts just two unlikely branches into
-the page allocator hotpath and if it returns false then allocation is
-done like as the kernel without page owner. These two unlikely branches
-would not affect to allocation performance. Following is the kernel's
-code size change due to this facility.
+the page allocator hotpath and if not enabled, then allocation is done
+like as the kernel without page owner. These two unlikely branches should
+not affect to allocation performance, especially if the static keys jump
+label patching functionality is available. Following is the kernel's code
+size change due to this facility.
 
 - Without page owner
    text    data     bss     dec     hex filename
diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
index cacaabe..8e2eb15 100644
--- a/include/linux/page_owner.h
+++ b/include/linux/page_owner.h
@@ -1,8 +1,10 @@
 #ifndef __LINUX_PAGE_OWNER_H
 #define __LINUX_PAGE_OWNER_H
 
+#include <linux/jump_label.h>
+
 #ifdef CONFIG_PAGE_OWNER
-extern bool page_owner_inited;
+extern struct static_key_false page_owner_inited;
 extern struct page_ext_operations page_owner_ops;
 
 extern void __reset_page_owner(struct page *page, unsigned int order);
@@ -12,27 +14,23 @@ extern gfp_t __get_page_owner_gfp(struct page *page);
 
 static inline void reset_page_owner(struct page *page, unsigned int order)
 {
-	if (likely(!page_owner_inited))
-		return;
-
-	__reset_page_owner(page, order);
+	if (static_branch_unlikely(&page_owner_inited))
+		__reset_page_owner(page, order);
 }
 
 static inline void set_page_owner(struct page *page,
 			unsigned int order, gfp_t gfp_mask)
 {
-	if (likely(!page_owner_inited))
-		return;
-
-	__set_page_owner(page, order, gfp_mask);
+	if (static_branch_unlikely(&page_owner_inited))
+		__set_page_owner(page, order, gfp_mask);
 }
 
 static inline gfp_t get_page_owner_gfp(struct page *page)
 {
-	if (likely(!page_owner_inited))
+	if (static_branch_unlikely(&page_owner_inited))
+		return __get_page_owner_gfp(page);
+	else
 		return 0;
-
-	return __get_page_owner_gfp(page);
 }
 #else
 static inline void reset_page_owner(struct page *page, unsigned int order)
diff --git a/mm/page_owner.c b/mm/page_owner.c
index f35826e..10a6a46 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();
 }
 
@@ -157,7 +158,7 @@ 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;
@@ -305,7 +306,7 @@ 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 53b722b..3f7ec14 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1117,7 +1117,7 @@ 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);
-- 
2.6.3

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Thread

[PATCH v2 0/9] page_owner improvements for debugging Vlastimil Babka <vbabka@suse.cz> - 2015-11-24 13:40 +0100
  [PATCH v2 4/9] mm, page_owner: copy page owner info during migration Vlastimil Babka <vbabka@suse.cz> - 2015-11-24 13:40 +0100
  [PATCH v2 3/9] mm, page_owner: convert page_owner_inited to static key Vlastimil Babka <vbabka@suse.cz> - 2015-11-24 13:40 +0100
    Re: [PATCH v2 3/9] mm, page_owner: convert page_owner_inited to  static key Michal Hocko <mhocko@kernel.org> - 2015-11-25 16:00 +0100
      Re: [PATCH v2 3/9] mm, page_owner: convert page_owner_inited to  static key Vlastimil Babka <vbabka@suse.cz> - 2015-11-25 16:10 +0100
        Re: [PATCH v2 3/9] mm, page_owner: convert page_owner_inited to  static key Peter Zijlstra <peterz@infradead.org> - 2015-11-25 16:30 +0100
          Re: [PATCH v2 3/9] mm, page_owner: convert page_owner_inited to  static key Michal Hocko <mhocko@kernel.org> - 2015-11-25 16:50 +0100
  [PATCH v2 2/9] mm, page_owner: print symbolic migratetype of both page and pageblock Vlastimil Babka <vbabka@suse.cz> - 2015-11-24 13:40 +0100
    Re: [PATCH v2 2/9] mm, page_owner: print symbolic migratetype of  both page and pageblock Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2015-11-25 09:20 +0100
  [PATCH v2 8/9] mm, page_alloc: print symbolic gfp_flags on allocation failure Vlastimil Babka <vbabka@suse.cz> - 2015-11-24 13:50 +0100
    Re: [PATCH v2 8/9] mm, page_alloc: print symbolic gfp_flags on  allocation failure Michal Hocko <mhocko@kernel.org> - 2015-11-25 15:40 +0100
  [PATCH v2 6/9] mm, debug: introduce dump_gfpflag_names() for symbolic printing of gfp_flags Vlastimil Babka <vbabka@suse.cz> - 2015-11-24 13:50 +0100
    Re: [PATCH v2 6/9] mm, debug: introduce dump_gfpflag_names() for  symbolic printing of gfp_flags Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2015-11-25 09:20 +0100
      Re: [PATCH v2 6/9] mm, debug: introduce dump_gfpflag_names() for  symbolic printing of gfp_flags Vlastimil Babka <vbabka@suse.cz> - 2015-11-25 11:30 +0100
        Re: [PATCH v2 6/9] mm, debug: introduce dump_gfpflag_names() for symbolic printing of gfp_flags yalin wang <yalin.wang2010@gmail.com> - 2015-11-27 04:50 +0100
  Re: [PATCH v2 0/9] page_owner improvements for debugging Michal Hocko <mhocko@kernel.org> - 2015-11-25 15:40 +0100

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