ios code is time-consuming statistics

Block code using convenient time consuming, as follows:

#import <mach/mach_time.h>   
  
CGFloat BNRTimeBlock (void (^block)(void)) {  
    mach_timebase_info_data_t info;  
    if (mach_timebase_info(&info) != KERN_SUCCESS) return -1.0;  
  
    uint64_t start = mach_absolute_time ();  
    block ();  
    uint64_t end = mach_absolute_time ();  
    uint64_t elapsed = end - start;  
  
    uint64_t nanos = elapsed * info.numer / info.denom;  
    return (CGFloat)nanos / NSEC_PER_SEC;  
}