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    Subject[PATCH RFC] x86: enforce inlining for atomics
    Date
    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@linutronix.de>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.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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