linux-kernel - [PATCH 1/3] linux/bitmap: Force inlining of bitmap weight functions

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Date:	Tue,  4 Aug 2015 16:15:14 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>, Thomas Graf <tgraf@...g.ch>,
	Peter Zijlstra <peterz@...radead.org>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] linux/bitmap: Force inlining of bitmap weight functions

With this config:
http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os

gcc-4.7.2 generates many copies of these tiny functions:

bitmap_weight (55 copies):
55                      push   %rbp
48 89 e5                mov    %rsp,%rbp
e8 3f 3a 8b 00          callq  __bitmap_weight
5d                      pop    %rbp
c3                      retq

hweight_long (23 copies):
55                      push   %rbp
e8 b5 65 8e 00          callq  __sw_hweight64
48 89 e5                mov    %rsp,%rbp
5d                      pop    %rbp
c3                      retq

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122

This patch fixes this via s/inline/__always_inline/

While at it, replaced two "__inline__" with usual "inline"
(the rest of the source file uses the latter).

    text     data      bss       dec     hex filename
86971357 17195880 36659200 140826437 864d745 vmlinux.before
86971120 17195912 36659200 140826232 864d678 vmlinux

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Thomas Graf <tgraf@...g.ch>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org
---
 include/linux/bitmap.h | 2 +-
 include/linux/bitops.h | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index ea17cca..9653fdb 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -295,7 +295,7 @@ static inline int bitmap_full(const unsigned long *src, unsigned int nbits)
 	return find_first_zero_bit(src, nbits) == nbits;
 }
 
-static inline int bitmap_weight(const unsigned long *src, unsigned int nbits)
+static __always_inline int bitmap_weight(const unsigned long *src, unsigned int nbits)
 {
 	if (small_const_nbits(nbits))
 		return hweight_long(*src & BITMAP_LAST_WORD_MASK(nbits));
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 297f5bd..e635533 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -57,7 +57,7 @@ extern unsigned long __sw_hweight64(__u64 w);
 	     (bit) < (size);					\
 	     (bit) = find_next_zero_bit((addr), (size), (bit) + 1))
 
-static __inline__ int get_bitmask_order(unsigned int count)
+static inline int get_bitmask_order(unsigned int count)
 {
 	int order;
 
@@ -65,7 +65,7 @@ static __inline__ int get_bitmask_order(unsigned int count)
 	return order;	/* We could be slightly more clever with -1 here... */
 }
 
-static __inline__ int get_count_order(unsigned int count)
+static inline int get_count_order(unsigned int count)
 {
 	int order;
 
@@ -75,7 +75,7 @@ static __inline__ int get_count_order(unsigned int count)
 	return order;
 }
 
-static inline unsigned long hweight_long(unsigned long w)
+static __always_inline unsigned long hweight_long(unsigned long w)
 {
 	return sizeof(w) == 4 ? hweight32(w) : hweight64(w);
 }
-- 
1.8.1.4

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