Messages in this thread Patch in this message | | | From | Denys Vlasenko <> | Subject | [PATCH RESEND] bufferhead: Force inlining of buffer head flag operations | Date | Fri, 5 Feb 2016 20:56:17 +0100 |
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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:
<set_buffer_mapped> (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 <buffer_mapped> (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 <set_buffer_new> (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 <dvlasenk@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Graf <tgraf@suug.ch> Cc: Peter Zijlstra <peterz@infradead.org> Cc: David Rientjes <rientjes@google.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: linux-kernel@vger.kernel.org ---
Resending. Verified that the results are still valid on the current Linus tree: savings are ~7k of code.
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 e6797de..50ccd04 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); \ } \ -- 1.8.1.4
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