Hi,
I wanted to adjust sampling period using PERF_EVENT_IOC_PERIOD ioctl.
I modified the notify_group to change the period at runtime as follows.
diff --git a/perf_examples/notify_group.c b/perf_examples/notify_group.c
index 76869b0..d8ff5e1 100644
--- a/perf_examples/notify_group.c
+++ b/perf_examples/notify_group.c
@@ -54,6 +54,7 @@ sigio_handler(int n, struct siginfo *info, struct
sigcontext *sc)
struct perf_event_mmap_page *hdr;
struct perf_event_header ehdr;
uint64_t ip;
+ uint64_t new_period;
int id, ret;
id = perf_fd2event(fds, num_fds, info->si_fd);
@@ -87,6 +88,11 @@ skip:
/*
* rearm the counter for one more shot
*/
+ new_period = SMPL_PERIOD * 2 ;
+ ret = ioctl(info->si_fd, PERF_EVENT_IOC_PERIOD, new_period);
+ if (ret == -1)
+ err(1, "cannot set");
+
ret = ioctl(info->si_fd, PERF_EVENT_IOC_REFRESH, 1);
if (ret == -1)
err(1, "cannot refresh");
It, however, failed to do so as belows.
$ ./notify_group
i=0 disabled=0
i=1 disabled=1
i=2 disabled=1
Notification 1: 0x8048f63 fd=3 PERF_COUNT_HW_CPU_CYCLES
notify_group: cannot set: Invalid argument
Any idea?
BTW, I found an error in perf_event.h of libpfm4 which prevents compiling
the code.
The following diff is the fix.
diff --git a/include/perfmon/perf_event.h b/include/perfmon/perf_event.h
index cfddef0..7f2889e 100644
--- a/include/perfmon/perf_event.h
+++ b/include/perfmon/perf_event.h
@@ -13,7 +13,7 @@
*/
#ifndef _LINUX_PERF_EVENT_H
#define _LINUX_PERF_EVENT_H
-
+#include <linux/types.h>
#include <sys/types.h>
#include <inttypes.h>
#ifndef PR_TASK_PERF_EVENTS_DISABLE
@@ -236,7 +236,7 @@ typedef struct perf_event_attr {
#define PERF_EVENT_IOC_DISABLE _IO ('$', 1)
#define PERF_EVENT_IOC_REFRESH _IO ('$', 2)
#define PERF_EVENT_IOC_RESET _IO ('$', 3)
-#define PERF_EVENT_IOC_PERIOD _IOW('$', 4, u64)
+#define PERF_EVENT_IOC_PERIOD _IOW('$', 4, __u64)
#define PERF_EVENT_IOC_SET_OUTPUT _IO ('$', 5)
#define PERF_EVENT_IOC_SET_FILTER _IOW('$', 6, char *)
- Heechul
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