Messages in this thread Patch in this message | | | From | Denys Vlasenko <> | Subject | [PATCH] force inlining of spinlock ops | Date | Mon, 13 Jul 2015 20:31:03 +0200 |
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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
In particular, with this config: http://busybox.net/~vda/kernel_config there are more than a thousand copies of tiny spinlock-related functions:
$ nm --size-sort vmlinux | grep -iF ' t ' | uniq -c | grep -v '^ *1 ' | sort -rn | grep ' spin' 473 000000000000000b t spin_unlock_irqrestore 292 000000000000000b t spin_unlock 215 000000000000000b t spin_lock 134 000000000000000b t spin_unlock_irq 130 000000000000000b t spin_unlock_bh 120 000000000000000b t spin_lock_irq 106 000000000000000b t spin_lock_bh
Disassembly:
ffffffff81004720 <spin_lock>: ffffffff81004720: 55 push %rbp ffffffff81004721: 48 89 e5 mov %rsp,%rbp ffffffff81004724: e8 f8 4e e2 02 callq <_raw_spin_lock> ffffffff81004729: 5d pop %rbp ffffffff8100472a: c3 retq
This patch fixes this via s/inline/__always_inline/ in spinlock.h. This decreases vmlinux by about 40k:
text data bss dec hex filename 82375570 22255544 20627456 125258570 7774b4a vmlinux.before 82335059 22255416 20627456 125217931 776ac8b vmlinux
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Graf <tgraf@suug.ch> Cc: Bart Van Assche <bvanassche@acm.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: David Rientjes <rientjes@google.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: linux-kernel@vger.kernel.org --- include/linux/spinlock.h | 30 +++++++++++++++--------------- 1 file changed, 15 insertions(+), 15 deletions(-)
diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index 3e18379..073925d 100644 --- a/include/linux/spinlock.h +++ b/include/linux/spinlock.h @@ -296,7 +296,7 @@ static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock) * Map the spin_lock functions to the raw variants for PREEMPT_RT=n */ -static inline raw_spinlock_t *spinlock_check(spinlock_t *lock) +static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock) { return &lock->rlock; } @@ -307,17 +307,17 @@ do { \ raw_spin_lock_init(&(_lock)->rlock); \ } while (0) -static inline void spin_lock(spinlock_t *lock) +static __always_inline void spin_lock(spinlock_t *lock) { raw_spin_lock(&lock->rlock); } -static inline void spin_lock_bh(spinlock_t *lock) +static __always_inline void spin_lock_bh(spinlock_t *lock) { raw_spin_lock_bh(&lock->rlock); } -static inline int spin_trylock(spinlock_t *lock) +static __always_inline int spin_trylock(spinlock_t *lock) { return raw_spin_trylock(&lock->rlock); } @@ -337,7 +337,7 @@ do { \ raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock); \ } while (0) -static inline void spin_lock_irq(spinlock_t *lock) +static __always_inline void spin_lock_irq(spinlock_t *lock) { raw_spin_lock_irq(&lock->rlock); } @@ -352,32 +352,32 @@ do { \ raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \ } while (0) -static inline void spin_unlock(spinlock_t *lock) +static __always_inline void spin_unlock(spinlock_t *lock) { raw_spin_unlock(&lock->rlock); } -static inline void spin_unlock_bh(spinlock_t *lock) +static __always_inline void spin_unlock_bh(spinlock_t *lock) { raw_spin_unlock_bh(&lock->rlock); } -static inline void spin_unlock_irq(spinlock_t *lock) +static __always_inline void spin_unlock_irq(spinlock_t *lock) { raw_spin_unlock_irq(&lock->rlock); } -static inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags) +static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags) { raw_spin_unlock_irqrestore(&lock->rlock, flags); } -static inline int spin_trylock_bh(spinlock_t *lock) +static __always_inline int spin_trylock_bh(spinlock_t *lock) { return raw_spin_trylock_bh(&lock->rlock); } -static inline int spin_trylock_irq(spinlock_t *lock) +static __always_inline int spin_trylock_irq(spinlock_t *lock) { return raw_spin_trylock_irq(&lock->rlock); } @@ -387,22 +387,22 @@ static inline int spin_trylock_irq(spinlock_t *lock) raw_spin_trylock_irqsave(spinlock_check(lock), flags); \ }) -static inline void spin_unlock_wait(spinlock_t *lock) +static __always_inline void spin_unlock_wait(spinlock_t *lock) { raw_spin_unlock_wait(&lock->rlock); } -static inline int spin_is_locked(spinlock_t *lock) +static __always_inline int spin_is_locked(spinlock_t *lock) { return raw_spin_is_locked(&lock->rlock); } -static inline int spin_is_contended(spinlock_t *lock) +static __always_inline int spin_is_contended(spinlock_t *lock) { return raw_spin_is_contended(&lock->rlock); } -static inline int spin_can_lock(spinlock_t *lock) +static __always_inline int spin_can_lock(spinlock_t *lock) { return raw_spin_can_lock(&lock->rlock); } -- 1.8.1.4
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