arm - How to get perf_event results for 2nd Nexus7 with Krait CPU -

all.

i try pmus information such instructions, cycle, cache miss , etc. on 2nd nexus7 krait cpu.

the perf tool not working correctly.

therefore, using follow sample source code in perf_event tutorials.

#include <stdlib.h> #include <stdio.h> #include <unistd.h> #include <string.h> #include <sys/ioctl.h> #include <linux/perf_event.h> #include <asm/unistd.h>  static long perf_event_open(struct perf_event_attr *hw_event, pid_t pid,         int cpu, int group_fd, unsigned long flags) {     int ret;      ret = syscall(__nr_perf_event_open, hw_event, pid, cpu,            group_fd, flags);     return ret; }  int main(int argc, char **argv) {     struct perf_event_attr pe;     long long count;     int fd;      memset(&pe, 0, sizeof(struct perf_event_attr));     pe.type = perf_type_hardware;     pe.size = sizeof(struct perf_event_attr);     pe.config = perf_count_hw_cpu_cycles;     pe.disabled = 1;     pe.exclude_kernel = 1;     pe.exclude_hv = 1;      fd = perf_event_open(&pe, 0, -1, -1, 0);     if (fd == -1) {        fprintf(stderr, "error opening leader %llx\n", pe.config);        exit(exit_failure);     }      ioctl(fd, perf_event_ioc_reset, 0);     ioctl(fd, perf_event_ioc_enable, 0);      printf("measuring cycles printf\n");      ioctl(fd, perf_event_ioc_disable, 0);     read(fd, &count, sizeof(long long));      printf("used %lld cycles", count);      close(fd); } 

i tried run code on x86 linux machine. result show "used 123123 cycles."

however, couldn't pmus event on 2nd nexus7. returns "used 0 cycles."

the pmu driver enabled follows.

<6>[ 0.152832] hw perfevents: enabled armv7 krait pmu driver, 5 counters available

also, can find perf_event_msm_krait.c in flo kernel 3.4 used nexus7. (i found patch supporting krait cpu; http://www.serverphorums.com/read.php?12,850329 . includes perf_event_cpu.c file couldn't find in kernel source. way correct in order support pmu nexus7 krait?)

thank in advance.