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

[Pratyush Anand <panand@redhat.com>]

Hi Peter,

On 24/02/2016:05:02:41 PM, Peter Zijlstra wrote:
> On Wed, Feb 24, 2016 at 03:02:39PM +0100, Peter Zijlstra wrote:
> > FWIW, it would be nice to have a similar test for:

+ Michael, (C Test case for following proposed test case is at the end)

> > 
> > 	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...

Thanks, Picked patches from your new series and it worked :-)

# perf stat -x';' -e 'probe_exact:*' examples/exact_counts  
65535;;probe_exact:f_65535x;85984820;100.00
997;;probe_exact:f_997x;85984820;100.00
103;;probe_exact:f_103x;85984820;100.00
3;;probe_exact:f_3x;85984820;100.00
2;;probe_exact:f_2x;85984820;100.00
1;;probe_exact:f_1x;85984820;100.00

~Pratyush

> 
> ---
> 
> #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;
> }