[PATCH 6/7] linux: Refactor sched_getcpu in terms of getcpu

[Adhemerval Zanella]

On 01/12/2019 11:22, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> diff --git a/sysdeps/unix/sysv/linux/sched_getcpu.c b/sysdeps/unix/sysv/linux/sched_getcpu.c
>> index 65dd9fdda7..3646c8b713 100644
>> --- a/sysdeps/unix/sysv/linux/sched_getcpu.c
>> +++ b/sysdeps/unix/sysv/linux/sched_getcpu.c
>> @@ -17,23 +17,11 @@
>>  
>>  #include <errno.h>
>>  #include <sched.h>
>> -#include <sysdep.h>
>> -
>> -#ifdef HAVE_GETCPU_VSYSCALL
>> -# define HAVE_VSYSCALL
>> -#endif
>> -#include <sysdep-vdso.h>
>>  
>>  int
>>  sched_getcpu (void)
>>  {
>> -#ifdef __NR_getcpu
>>    unsigned int cpu;
>> -  int r = INLINE_VSYSCALL (getcpu, 3, &cpu, NULL, NULL);
>> -
>> +  int r = __getcpu (&cpu, NULL);
>>    return r == -1 ? r : cpu;
>> -#else
>> -  __set_errno (ENOSYS);
>> -  return -1;
>> -#endif
>>  }
> 
> I wonder if the current state is a useful performance optimization.
> 

I thought about that, another option would be to create an internal
header with a static inline implementation where both sched_getcpu
and getcpu will use and thus removing the function call overhead
while continuing to provide only one code that issue the vDSO/syscall.