linux-kernel - [PATCH 3/3] jiffies: Force inlining of {m,u}msecs_to

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Date:	Tue,  4 Aug 2015 16:15:16 +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 3/3] jiffies: Force inlining of {m,u}msecs_to_jiffies()

With this config:
http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os
gcc-4.7.2 generates many copies of these tiny functions:

msecs_to_jiffies (45 copies):
55                      push   %rbp
48 89 e5                mov    %rsp,%rbp
e8 59 ec 03 00          callq  __msecs_to_jiffies
5d                      pop    %rbp
c3                      retq

usecs_to_jiffies (10 copies):
55                      push   %rbp
48 89 e5                mov    %rsp,%rbp
e8 5d 54 5e ff          callq  __usecs_to_jiffies
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/

    text     data      bss       dec     hex filename
86970954 17195912 36659200 140826066 864d5d2 vmlinux.before
86966150 17195912 36659200 140821262 864c30e 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/jiffies.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
index 535fd3b..1ba48a1 100644
--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -351,7 +351,7 @@ static inline unsigned long _msecs_to_jiffies(const unsigned int m)
  * directly here and from __msecs_to_jiffies() in the case where
  * constant folding is not possible.
  */
-static inline unsigned long msecs_to_jiffies(const unsigned int m)
+static __always_inline unsigned long msecs_to_jiffies(const unsigned int m)
 {
 	if (__builtin_constant_p(m)) {
 		if ((int)m < 0)
@@ -405,7 +405,7 @@ static inline unsigned long _usecs_to_jiffies(const unsigned int u)
  * directly here and from __msecs_to_jiffies() in the case where
  * constant folding is not possible.
  */
-static inline unsigned long usecs_to_jiffies(const unsigned int u)
+static __always_inline unsigned long usecs_to_jiffies(const unsigned int u)
 {
 	if (__builtin_constant_p(u)) {
 		if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
-- 
1.8.1.4

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