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Date: Mon, 20 Apr 2015 23:27:11 +0200
From: Hagen Paul Pfeifer <hagen@...u.net>
To: linux-kernel@...r.kernel.org
Cc: Hagen Paul Pfeifer <hagen@...u.net>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH RFC] x86: enforce inlining for atomics
During some code analysis I realized that atomic_add, atomic_sub and
friends are not necessarily inlined AND that each function is defined
multiple times:
atomic_inc: 544 duplicates
atomic_dec: 215 duplicates
atomic_dec_and_test: 107 duplicates
atomic64_inc: 38 duplicates
[...]
Each definition is exact equally, e.g.:
ffffffff813171b8 <atomic_add>:
55 push %rbp
48 89 e5 mov %rsp,%rbp
f0 01 3e lock add %edi,(%rsi)
5d pop %rbp
c3 retq
In turn each definition has one or more callsites (sure):
ffffffff81317c78: e8 3b f5 ff ff callq ffffffff813171b8 <atomic_add>
[...]
ffffffff8131a062: e8 51 d1 ff ff callq ffffffff813171b8 <atomic_add>
[...]
ffffffff8131a190: e8 23 d0 ff ff callq ffffffff813171b8 <atomic_add>
[...]
The other way around would be to remove the static linkage - but I prefer
an enforced inlining here.
Before:
text data bss dec hex filename
81467393 19874720 20168704 121510817 73e1ba1 vmlinux.orig
After:
text data bss dec hex filename
81461323 19874720 20168704 121504747 73e03eb vmlinux.inlined
Yes, the inlining here makes the kernel even smaller! ;)
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Hagen Paul Pfeifer <hagen@...u.net>
---
arch/x86/include/asm/atomic.h | 16 ++++++++--------
arch/x86/include/asm/atomic64_64.h | 8 ++++----
2 files changed, 12 insertions(+), 12 deletions(-)
diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h
index 5e5cd12..75a9ee8 100644
--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -46,7 +46,7 @@ static inline void atomic_set(atomic_t *v, int i)
*
* Atomically adds @i to @v.
*/
-static inline void atomic_add(int i, atomic_t *v)
+static __always_inline void atomic_add(int i, atomic_t *v)
{
asm volatile(LOCK_PREFIX "addl %1,%0"
: "+m" (v->counter)
@@ -60,7 +60,7 @@ static inline void atomic_add(int i, atomic_t *v)
*
* Atomically subtracts @i from @v.
*/
-static inline void atomic_sub(int i, atomic_t *v)
+static __always_inline void atomic_sub(int i, atomic_t *v)
{
asm volatile(LOCK_PREFIX "subl %1,%0"
: "+m" (v->counter)
@@ -76,7 +76,7 @@ static inline void atomic_sub(int i, atomic_t *v)
* true if the result is zero, or false for all
* other cases.
*/
-static inline int atomic_sub_and_test(int i, atomic_t *v)
+static __always_inline int atomic_sub_and_test(int i, atomic_t *v)
{
GEN_BINARY_RMWcc(LOCK_PREFIX "subl", v->counter, "er", i, "%0", "e");
}
@@ -87,7 +87,7 @@ static inline int atomic_sub_and_test(int i, atomic_t *v)
*
* Atomically increments @v by 1.
*/
-static inline void atomic_inc(atomic_t *v)
+static __always_inline void atomic_inc(atomic_t *v)
{
asm volatile(LOCK_PREFIX "incl %0"
: "+m" (v->counter));
@@ -99,7 +99,7 @@ static inline void atomic_inc(atomic_t *v)
*
* Atomically decrements @v by 1.
*/
-static inline void atomic_dec(atomic_t *v)
+static __always_inline void atomic_dec(atomic_t *v)
{
asm volatile(LOCK_PREFIX "decl %0"
: "+m" (v->counter));
@@ -113,7 +113,7 @@ static inline void atomic_dec(atomic_t *v)
* returns true if the result is 0, or false for all other
* cases.
*/
-static inline int atomic_dec_and_test(atomic_t *v)
+static __always_inline int atomic_dec_and_test(atomic_t *v)
{
GEN_UNARY_RMWcc(LOCK_PREFIX "decl", v->counter, "%0", "e");
}
@@ -152,7 +152,7 @@ static inline int atomic_add_negative(int i, atomic_t *v)
*
* Atomically adds @i to @v and returns @i + @v
*/
-static inline int atomic_add_return(int i, atomic_t *v)
+static __always_inline int atomic_add_return(int i, atomic_t *v)
{
return i + xadd(&v->counter, i);
}
@@ -191,7 +191,7 @@ static inline int atomic_xchg(atomic_t *v, int new)
* Atomically adds @a to @v, so long as @v was not already @u.
* Returns the old value of @v.
*/
-static inline int __atomic_add_unless(atomic_t *v, int a, int u)
+static __always_inline int __atomic_add_unless(atomic_t *v, int a, int u)
{
int c, old;
c = atomic_read(v);
diff --git a/arch/x86/include/asm/atomic64_64.h b/arch/x86/include/asm/atomic64_64.h
index f8d273e..b965f9e 100644
--- a/arch/x86/include/asm/atomic64_64.h
+++ b/arch/x86/include/asm/atomic64_64.h
@@ -40,7 +40,7 @@ static inline void atomic64_set(atomic64_t *v, long i)
*
* Atomically adds @i to @v.
*/
-static inline void atomic64_add(long i, atomic64_t *v)
+static __always_inline void atomic64_add(long i, atomic64_t *v)
{
asm volatile(LOCK_PREFIX "addq %1,%0"
: "=m" (v->counter)
@@ -81,7 +81,7 @@ static inline int atomic64_sub_and_test(long i, atomic64_t *v)
*
* Atomically increments @v by 1.
*/
-static inline void atomic64_inc(atomic64_t *v)
+static __always_inline void atomic64_inc(atomic64_t *v)
{
asm volatile(LOCK_PREFIX "incq %0"
: "=m" (v->counter)
@@ -94,7 +94,7 @@ static inline void atomic64_inc(atomic64_t *v)
*
* Atomically decrements @v by 1.
*/
-static inline void atomic64_dec(atomic64_t *v)
+static __always_inline void atomic64_dec(atomic64_t *v)
{
asm volatile(LOCK_PREFIX "decq %0"
: "=m" (v->counter)
@@ -148,7 +148,7 @@ static inline int atomic64_add_negative(long i, atomic64_t *v)
*
* Atomically adds @i to @v and returns @i + @v
*/
-static inline long atomic64_add_return(long i, atomic64_t *v)
+static __always_inline long atomic64_add_return(long i, atomic64_t *v)
{
return i + xadd(&v->counter, i);
}
--
2.1.4
--
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