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It has been said that local_lock() does not add any overhead compared to preempt_disable() in a !LOCKDEP configuration. A micro benchmark showed an unexpected result which can be reduced to the fact that local_lock() was not entirely optimized away. In the !LOCKDEP configuration local_lock_acquire() is an empty static inline function. On x86 the this_cpu_ptr() argument of that function is fully evaluated leading to an additional mov+add instructions which are not needed and not used. Replace the static inline function with a macro. The typecheck() macro ensures that the argument is of proper type while the resulting disassembly shows no traces of this_cpu_ptr(). Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Waiman Long <longman@redhat.com> Link: https://lkml.kernel.org/r/YgKjciR60fZft2l4@linutronix.de |
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