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Subject[PATCH 0/4] perf_counter: Group reads and other patches
So Ingo really wanted to not break the current read() ABI, which is possible
with a little bit more code. Hence here a second version.

The test proglet below gives:

# gcc -o test test.c; ./test
EVNT: 0x400851 scale: nan ID: 646 CNT: 1006656 ID: 647 CNT: 1011020 ID: 648 CNT: 1011120 ID: 649 CNT: 1011079
EVNT: 0x40084b scale: 1.000000 ID: 646 CNT: 2002513 ID: 647 CNT: 2009368 ID: 648 CNT: 2009756 ID: 649 CNT: 2010162
EVNT: 0x40084b scale: 1.000000 ID: 646 CNT: 3002611 ID: 647 CNT: 3013444 ID: 648 CNT: 3014276 ID: 649 CNT: 3015129
EVNT: 0x400858 scale: 1.000000 ID: 646 CNT: 4002528 ID: 647 CNT: 4017221 ID: 648 CNT: 4018497 ID: 649 CNT: 4019802
EVNT: 0x40084b scale: 1.000000 ID: 646 CNT: 5002324 ID: 647 CNT: 5020652 ID: 648 CNT: 5022372 ID: 649 CNT: 5024119
EVNT: 0x40084c scale: 1.000000 ID: 646 CNT: 6002555 ID: 647 CNT: 6024466 ID: 648 CNT: 6026635 ID: 649 CNT: 6028829
and an the regular perf stuff also still works:

# perf stat sleep 1

Performance counter stats for 'sleep 1':

4.164737 task-clock-msecs # 0.004 CPUs
1 context-switches # 0.000 M/sec
0 CPU-migrations # 0.000 M/sec
186 page-faults # 0.045 M/sec
4109598 cycles # 986.761 M/sec
2573031 instructions # 0.626 IPC
1268929 cache-references # 304.684 M/sec
13059 cache-misses # 3.136 M/sec


---
#include "perf.h"
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>
#include <signal.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>

void work(void)
{
int i;
for (i = 0; i < 1000000; i++) {
asm("nop");
asm("nop");
asm("nop");
asm("nop");
asm("nop");
asm("nop");
asm("nop");
}
}
unsigned long page_size;
int fd = -1, fd1 = 0;
pid_t me;
void *output;

void handle_sigio(int sig)
{
ioctl(fd, PERF_COUNTER_IOC_REFRESH, 1);
}
static unsigned long mmap_read_head(void)
{
struct perf_counter_mmap_page *pc = output;
long head;
head = pc->data_head;
rmb();

return head;
}
static void *mmap_read_base(void)
{
return output + page_size;
}
struct event {
struct perf_event_header header;
u64 ip;
u64 nr;
u64 time_enabled;
u64 time_running;
struct {
u64 val;
u64 id;
} cnt[0];
};
int main(int argc, char **argv)
{
struct perf_counter_attr attr;
unsigned long offset = 0, head;
int err, i;
page_size = sysconf(_SC_PAGE_SIZE);
me = getpid();

memset(&attr, 0, sizeof(attr));

attr.type = PERF_TYPE_HARDWARE;
attr.config = PERF_COUNT_HW_CPU_CYCLES;
attr.sample_period = 1000000;
attr.sample_type = PERF_SAMPLE_IP |
PERF_SAMPLE_READ;
attr.read_format = PERF_FORMAT_TOTAL_TIME_RUNNING |
PERF_FORMAT_TOTAL_TIME_ENABLED |
PERF_FORMAT_ID |
PERF_FORMAT_GROUP;
attr.disabled = 1;
attr.wakeup_events = 1;
fd = sys_perf_counter_open(&attr, me, -1, fd, 0);
if (fd <= 0) {
perror("FAIL fd: ");
exit(-1);
}
attr.sample_period = 0;
attr.disabled = 0;

for (i = 0; i < 3; i++) {
fd1 = sys_perf_counter_open(&attr, me, -1, fd, 0);
if (fd1 <= 0) {
perror("FAIL fd1: ");
exit(-1);
}
}
signal(SIGIO, handle_sigio);
err = fcntl(fd, F_SETOWN, me);
if (err == -1) {
perror("FAIL fcntl: ");
exit(-1);
}
err = fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_ASYNC);
if (err == -1) {
perror("FAIL fcntl2: ");
exit(-1);
}
output = mmap(NULL, page_size * 3, PROT_READ, MAP_SHARED, fd, 0);
if (output == ((void *)-1)) {
perror("FAIL mmap:");
exit(-1);
}
ioctl(fd, PERF_COUNTER_IOC_REFRESH, 1);

work();

ioctl(fd, PERF_COUNTER_IOC_DISABLE, 0);

head = mmap_read_head();

for (; offset < head; ) {
struct event *evnt = mmap_read_base() + offset;
offset += evnt->header.size;

printf("EVNT: %p scale: %f ", (void *)evnt->ip,
((double)evnt->time_running)/evnt->time_enabled
);
for (i = 0; i < evnt->nr; i++) {
printf("ID: %Lu CNT: %Lu ",
evnt->cnt[i].id, evnt->cnt[i].val);
}
printf("\n");
}
return 0;
}


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