Re: [RFC][PATCH 4/7] perf: Fix scaling vs enable_on_exec

[Peter Zijlstra]

On Wed, Feb 24, 2016 at 03:02:39PM +0100, Peter Zijlstra wrote:
> FWIW, it would be nice to have a similar test for:
> 
>       attr = {
>               .disabled = true;
>       }
> 
>       sys_perf_event_open(&attr, .pid = self);
> 
>       if (attr.disabled)
>               ioctl(ENABLE);
> 
>       /* generate N events */
> 
>       ioctl(DISABLE);
> 
>       read();
> 
>       /* print event cnt and scale factors */
> 
> and one that has .disabled = false.


root@ivb-ep:~/perf# ./main 
1000000903 218851613 218851613
root@ivb-ep:~/perf# ./main 1
1000000235 218981231 218981231


Appears to work...

---

#define _GNU_SOURCE
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

#include "perf.h"

static struct perf_event_attr perf_attr = {
        .type = PERF_TYPE_HARDWARE,
        .config = PERF_COUNT_HW_INSTRUCTIONS,
        .read_format = PERF_FORMAT_TOTAL_TIME_ENABLED |
                       PERF_FORMAT_TOTAL_TIME_RUNNING,
        .exclude_kernel = 1,
        .pinned = 1,
};

void die(const char *err, ...)
{
        va_list params;

        va_start(params, err);
        vfprintf(stderr, err, params);
        va_end(params);

        exit(-1);
}

int main (int argc, char **argv)
{
        u64 val[3];
        int i, fd;

        perf_attr.disabled = argc > 1;

        fd = sys_perf_event_open(&perf_attr, 0, -1, -1, 0);
        if (fd < 0)
                die("failed to create perf_event");

        if (perf_attr.disabled)
                ioctl(fd, PERF_EVENT_IOC_ENABLE, 0);

        for (i = 0; i < 100000000; i++) {
                asm volatile ("nop\n\r"
                              "nop\n\r"
                              "nop\n\r"
                              "nop\n\r"
                              "nop\n\r"
                              "nop\n\r"
                              "nop\n\r");
        }

        ioctl(fd, PERF_EVENT_IOC_DISABLE, 0);

        read(fd, &val, sizeof(val));

        printf("%Lu %Lu %Lu\n", val[0], val[1], val[2]);

        return 0;
}