On Thu, Aug 13, 2009 at 11:56 AM, Ingo Molnar<mingo@elte.hu> wrote:
Here it is. It assumes you have enabled PCE in CR4 on all your CPUs.
I used BRANCH to ensure it would not use a fixed counter given the
hdr->index is wrong for those.
#include <sys/types.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
#include <sys/mman.h>
#include <err.h>
#include <perf_counter.h>
#ifdef __x86_64__
#define DECLARE_ARGS(val, low, high) unsigned low, high
#define EAX_EDX_VAL(val, low, high) ((low) | ((uint64_t )(high) << 32))
#define EAX_EDX_ARGS(val, low, high) "a" (low), "d" (high)
#define EAX_EDX_RET(val, low, high) "=a" (low), "=d" (high)
#else
#define DECLARE_ARGS(val, low, high) unsigned long long val
#define EAX_EDX_VAL(val, low, high) (val)
#define EAX_EDX_ARGS(val, low, high) "A" (val)
#define EAX_EDX_RET(val, low, high) "=A" (val)
#endif
#define barrier() __asm__ __volatile__("": : :"memory")
static inline unsigned long long rdpmc(int counter)
{
unsigned low, high;
asm volatile("rdpmc" : EAX_EDX_RET(val, low, high) : "c" (counter));
return EAX_EDX_VAL(val, low, high);
}
static volatile int quit;
void sig_handler(int n)
{
quit = 1;
}
/*
* our test code (function cannot be made static otherwise it is optimized away)
*/
unsigned long
fib(unsigned long n)
{
if (n == 0)
return 0;
if (n == 1)
return 2;
return fib(n-1)+fib(n-2);
}
int
main(int argc, char **argv)
{
struct perf_counter_mmap_page *hdr;
struct perf_counter_attr hw;
char *name;
uint64_t values[3];
int ret, fd, src;
unsigned int seq;
memset(&hw, 0, sizeof(hw));
/* make sure we do not use a fixed counter event */
name = "PERF_COUNT_HW_BRANCH_INSTRUCTIONS";
hw.type = PERF_TYPE_HARDWARE;
hw.config = PERF_COUNT_HW_BRANCH_INSTRUCTIONS;
hw.read_format =
PERF_FORMAT_TOTAL_TIME_ENABLED|PERF_FORMAT_TOTAL_TIME_RUNNING;
hw.disabled = 0;
fd = perf_counter_open(&hw, 0, -1, -1, 0);
if (fd == -1)
err(1, "cannot open event");
hdr = mmap(NULL, getpagesize(), PROT_READ, MAP_SHARED, fd, 0);
if (hdr == MAP_FAILED)
err(1, "cannot mmap page");
signal(SIGALRM, sig_handler);
ioctl(fd, PERF_COUNTER_IOC_ENABLE, 0);
alarm(10);
for(;quit == 0;) {
uint64_t offset = 0;
unsigned long loop;
/* generate branches */
fib(10);
loop = 0;
do {
loop++;
seq = hdr->lock;
barrier();
if (hdr->index > 0) {
values[0] = rdpmc(hdr->index-1);
offset = hdr->offset;
values[0] += offset;
values[1] = hdr->time_enabled;
values[2] = hdr->time_running;
src = 0;
} else {
ret = read(fd, values, sizeof(values));
src =1;
break;
}
barrier();
} while (hdr->lock != seq);
if (values[2])
values[0]= (uint64_t)((double)values[0] *
values[1]/values[2]);
printf("%20"PRIx64" %s %s offset=0x%"PRIx64" src=%s loop=%lu\n",
values[0],
name,
values[1] != values[2] ? "(scaled)" : "",
offset, src ? "read" : "rdpmc",
loop);
}
ioctl(fd, PERF_COUNTER_IOC_DISABLE, 0);
close(fd);
return 0;
}
--
