On Tue, Mar 31, 2015 at 01:33:38PM -0700, Andrew Morton wrote:
> On Tue, 31 Mar 2015 17:35:34 +0300 "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> wrote:
>
> > On Tue, Mar 31, 2015 at 08:11:02AM -0500, Christoph Lameter wrote:
> > > On Tue, 31 Mar 2015, Kirill A. Shutemov wrote:
> > >
> > > > Let's use PageAnon() and PageKsm() helpers instead. It helps readability
> > > > and makes page_anon_vma() work correctly on tail pages.
> > >
> > > But it adds a branch due to the use of ||.
> >
> > Which caller is hot enough to care?
> >
>
> It's a surprisingly expensive patch.
>
> text data bss dec hex filename
>
> 19984 1153 15192 36329 8de9 mm/ksm.o-before
> 20028 1153 15216 36397 8e2d mm/ksm.o-after
>
> 14728 116 5168 20012 4e2c mm/rmap.o-before
> 14763 116 5192 20071 4e67 mm/rmap.o-after
>
> 25723 1417 9776 36916 9034 mm/swapfile.o-before
> 25769 1417 9800 36986 907a mm/swapfile.o-after
>
> 197 bytes more text+bss, 125 bytes more text.
>
> (Why the heck do changes like this allegedly affect bss size?)
What about this?
>From adc384977898173d65c2567fc5eb421da9b272e0 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Date: Wed, 1 Apr 2015 14:33:56 +0300
Subject: [PATCH] mm: uninline and cleanup page-mapping related helpers
Most-used page->mapping helper -- page_mapping() -- has already
uninlined. Let's uninline also page_rmapping() and page_anon_vma().
It saves us depending on configuration around 400 bytes in text:
text data bss dec hex filename
660318 99254 410000 1169572 11d8a4 mm/built-in.o-before
659854 99254 410000 1169108 11d6d4 mm/built-in.o
As side effect page_anon_vma() now works properly on tail pages.
I also tried to make code a bit more clean.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
include/linux/mm.h | 9 ++-------
include/linux/rmap.h | 8 --------
mm/util.c | 42 ++++++++++++++++++++++++++++++++++++------
3 files changed, 38 insertions(+), 21 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 4a3a38522ab4..0d73890afc2b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -910,15 +910,10 @@ void page_address_init(void);
#define page_address_init() do { } while(0)
#endif
+extern void *page_rmapping(struct page *page);
+extern struct anon_vma *page_anon_vma(struct page *page);
extern struct address_space *page_mapping(struct page *page);
-/* Neutral page->mapping pointer to address_space or anon_vma or other */
-static inline void *page_rmapping(struct page *page)
-{
- page = compound_head(page);
- return (void *)((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);
-}
-
extern struct address_space *__page_file_mapping(struct page *);
static inline
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 9c5ff69fa0cd..bf36b6e644c4 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -106,14 +106,6 @@ static inline void put_anon_vma(struct anon_vma *anon_vma)
__put_anon_vma(anon_vma);
}
-static inline struct anon_vma *page_anon_vma(struct page *page)
-{
- if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
- PAGE_MAPPING_ANON)
- return NULL;
- return page_rmapping(page);
-}
-
static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
{
struct anon_vma *anon_vma = vma->anon_vma;
diff --git a/mm/util.c b/mm/util.c
index 769a7a2870af..426f303f8030 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -355,12 +355,39 @@ void kvfree(const void *addr)
}
EXPORT_SYMBOL(kvfree);
+static inline void * __page_rmapping(struct page *page)
+{
+ unsigned long mapping;
+
+ mapping = (unsigned long)page->mapping;
+ mapping &= ~PAGE_MAPPING_FLAGS;
+
+ return (void *)mapping;
+}
+
+/* Neutral page->mapping pointer to address_space or anon_vma or other */
+void *page_rmapping(struct page *page)
+{
+ page = compound_head(page);
+ return __page_rmapping(page);
+}
+
+struct anon_vma *page_anon_vma(struct page *page)
+{
+ unsigned long mapping;
+
+ page = compound_head(page);
+ mapping = (unsigned long)page->mapping;
+ if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
+ return NULL;
+ return __page_rmapping(page);
+}
+
struct address_space *page_mapping(struct page *page)
{
- struct address_space *mapping;
+ unsigned long mapping;
page = compound_head(page);
- mapping = page->mapping;
/* This happens if someone calls flush_dcache_page on slab page */
if (unlikely(PageSlab(page)))
@@ -370,10 +397,13 @@ struct address_space *page_mapping(struct page *page)
swp_entry_t entry;
entry.val = page_private(page);
- mapping = swap_address_space(entry);
- } else if ((unsigned long)mapping & PAGE_MAPPING_ANON)
- mapping = NULL;
- return mapping;
+ return swap_address_space(entry);
+ }
+
+ mapping = (unsigned long)page->mapping;
+ if (mapping & PAGE_MAPPING_FLAGS)
+ return NULL;
+ return page->mapping;
}
int overcommit_ratio_handler(struct ctl_table *table, int write,
--
Kirill A. Shutemov
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