linux_perf_event: add make_linux_perf_event

Refactor the common code making linux_perf_event out of
`user_instructions_retired` and `user_cpu_cycles_retired`.

Signed-off-by: Benny Halevy <[email protected]>

tests/perf/linux_perf_event.cc

@@ -81,28 +81,25 @@ linux_perf_event::disable() {
  ::ioctl(_fd, PERF_EVENT_IOC_DISABLE, 0);
 }
 
-linux_perf_event
-linux_perf_event::user_instructions_retired() {
+static linux_perf_event
+make_linux_perf_event(unsigned config, pid_t pid = 0, int cpu = -1, int group_fd = -1, unsigned long flags = 0) {
  return linux_perf_event(perf_event_attr{
  .type = PERF_TYPE_HARDWARE,
  .size = sizeof(struct perf_event_attr),
- .config = PERF_COUNT_HW_INSTRUCTIONS,
+ .config = config,
  .disabled = 1,
  .exclude_kernel = 1,
  .exclude_hv = 1,
  .exclude_idle = 1,
- }, 0, -1, -1, 0);
+ }, pid, cpu, group_fd, flags);
+}
+
+linux_perf_event
+linux_perf_event::user_instructions_retired() {
+ return make_linux_perf_event(PERF_COUNT_HW_INSTRUCTIONS);
 }
 
 linux_perf_event
 linux_perf_event::user_cpu_cycles_retired() {
- return linux_perf_event(perf_event_attr{
- .type = PERF_TYPE_HARDWARE,
- .size = sizeof(struct perf_event_attr),
- .config = PERF_COUNT_HW_CPU_CYCLES,
- .disabled = 1,
- .exclude_kernel = 1,
- .exclude_hv = 1,
- .exclude_idle = 1,
- }, 0, -1, -1, 0);
+ return make_linux_perf_event(PERF_COUNT_HW_CPU_CYCLES);
 }