From ee91ef6173e81819f5ff610c2485802081635657 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Thu, 17 Mar 2016 14:18:21 -0700 Subject: [PATCH] bufferhead: force inlining of buffer head flag operations With both gcc 4.7.2 and 4.9.2, sometimes gcc mysteriously doesn't inline very small functions we expect to be inlined. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122 With this .config: http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os, set_buffer_foo(), clear_buffer_foo() and similar functions get deinlined about 60 times. Examples of disassembly: (14 copies, 43 calls): 55 push %rbp 48 89 e5 mov %rsp,%rbp f0 80 0f 20 lock orb $0x20,(%rdi) 5d pop %rbp c3 retq (3 copies, 34 calls): 48 8b 07 mov (%rdi),%rax 55 push %rbp 48 89 e5 mov %rsp,%rbp 48 c1 e8 05 shr $0x5,%rax 83 e0 01 and $0x1,%eax 5d pop %rbp c3 retq (5 copies, 13 calls): 55 push %rbp 48 89 e5 mov %rsp,%rbp f0 80 0f 40 lock orb $0x40,(%rdi) 5d pop %rbp c3 retq This patch fixes this via s/inline/__always_inline/. This decreases vmlinux by about 3 kbytes. text data bss dec hex filename 88200439 19905208 36421632 144527279 89d4faf vmlinux2 88197239 19905240 36421632 144524111 89d434f vmlinux Signed-off-by: Denys Vlasenko Cc: Ingo Molnar Cc: Thomas Graf Cc: Peter Zijlstra Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/buffer_head.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index 89d9aa9e79bf..c67f052cc5e5 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -82,15 +82,15 @@ struct buffer_head { * and buffer_foo() functions. */ #define BUFFER_FNS(bit, name) \ -static inline void set_buffer_##name(struct buffer_head *bh) \ +static __always_inline void set_buffer_##name(struct buffer_head *bh) \ { \ set_bit(BH_##bit, &(bh)->b_state); \ } \ -static inline void clear_buffer_##name(struct buffer_head *bh) \ +static __always_inline void clear_buffer_##name(struct buffer_head *bh) \ { \ clear_bit(BH_##bit, &(bh)->b_state); \ } \ -static inline int buffer_##name(const struct buffer_head *bh) \ +static __always_inline int buffer_##name(const struct buffer_head *bh) \ { \ return test_bit(BH_##bit, &(bh)->b_state); \ } @@ -99,11 +99,11 @@ static inline int buffer_##name(const struct buffer_head *bh) \ * test_set_buffer_foo() and test_clear_buffer_foo() */ #define TAS_BUFFER_FNS(bit, name) \ -static inline int test_set_buffer_##name(struct buffer_head *bh) \ +static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \ { \ return test_and_set_bit(BH_##bit, &(bh)->b_state); \ } \ -static inline int test_clear_buffer_##name(struct buffer_head *bh) \ +static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \ { \ return test_and_clear_bit(BH_##bit, &(bh)->b_state); \ } \ -- 2.20.1