68             perf_event_mmap_page.data_tail = 0;  in init()
82     fn can_write(&self, data_size: usize, data_tail: usize, data_head: usize) -> bool {  in can_write()
83         if (data_head + 1) % self.data_region_size == data_tail {  in can_write()
87         let capacity = if data_head >= data_tail {  in can_write()
88             self.data_region_size - data_head + data_tail  in can_write()
90             data_tail - data_head  in can_write()
96         let data_tail = unsafe { &mut (*(self.ptr as *mut perf_event_mmap_page)).data_tail };  in write_event()  localVariable
103             self.can_write(sample_size, *data_tail as usize, *data_head as usize);  in write_event()
127                 *data_tail as usize,  in write_event()
207         let data_tail = unsafe { &(*(self.ptr as *mut perf_event_mmap_page)).data_tail };  in readable()  localVariable
209         data_tail != data_head  in readable()