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/* Copyright (c) 2015, Linaro Limited
* All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
/*
* Program to read perf counter on ARMv8 from userspace using mmap way
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/syscall.h>
#include <linux/perf_event.h>
#include <linux/types.h>
#include <sys/mman.h>
#include <errno.h>
#include <string.h>
#include <getopt.h>
#include <math.h>
#define barrier() asm volatile("dmb ish" : : : "memory")
#define isb() asm volatile("isb" : : : "memory")
#define ARMV8_PMCNTENSET_EL0_ENABLE (1<<31) /**< Enable Perf count reg */
static int fddev = -1;
static unsigned long page_size;
static int counter_init(unsigned int counter)
{
static struct perf_event_attr attr;
attr.type = PERF_TYPE_HARDWARE;
if (counter < 0 || counter > PERF_COUNT_HW_MAX)
return -1;
attr.config = counter;
fddev = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);
if (fddev == -1) {
fprintf(stderr,
"Error opening perf_event_open for counter %llx\n",
attr.config);
return -1;
}
return 0;
}
static unsigned long rdpmc(unsigned int counter)
{
unsigned long int ret;
if (counter == PERF_COUNT_HW_CPU_CYCLES)
asm volatile("mrs %0, pmccntr_el0" : "=r" (ret));
else {
asm volatile("msr pmselr_el0, %0" : : "r" ((counter-1)));
asm volatile("mrs %0, pmxevcntr_el0" : "=r" (ret));
}
isb();
return ret;
}
static unsigned long mmap_read_self(void *addr)
{
struct perf_event_mmap_page *pc = addr;
unsigned int seq, idx;
unsigned long count;
signed long pmc = 0;
do {
count = 0;
seq = pc->lock;
barrier();
idx = pc->index;
if (idx)
pmc = rdpmc(idx - 1);
barrier();
} while (pc->lock != seq);
count = pmc;
return count;
}
/* loop body to keep things interested. Make sure it gets inlined. */
static inline int
loop(int* __restrict__ a, int* __restrict__ b, int n)
{
unsigned sum = 0;
int i = 0;
for (i = 0; i < n; ++i)
if (a[i] > b[i])
sum += a[i] + 5;
return sum;
}
void print_usage(char *argv)
{
printf("Usage: %s -c perf_hw_counter -n length\n"
"%s - read perf hardware counters from userspace\n\n"
"-c\t perf_hw_counter is enum value of hw counter for platform\n"
"Refer to 'enum perf_hw_id'[file <linux/perf_event.h>] for hw\n"
"counter enum value in range of 0 to PERF_COUNT_HW_MAX\n"
"-n\t Length size array will implement busyloop\n"
"e.g.\n"
"\t%s -c 0 -n 64\n", argv, argv, argv);
}
int main(int ac, char *argv[])
{
int option = 0;
int *a = NULL;
int *b = NULL;
int len = -1, cnt = -1;
int i, pre_loop_res, post_loop_res, sum = 0;
void *addr; /* mmaped address */
unsigned long start_count, stop_count;
while ((option = getopt(ac, argv, "c:n:")) != -1) {
switch (option) {
case 'c':
cnt = atoi(optarg);
break;
case 'n':
len = atoi(optarg);
break;
default:
print_usage(argv[0]);
exit(EXIT_FAILURE);
}
}
if (len == -1 || cnt == -1) {
print_usage(argv[0]);
exit(EXIT_FAILURE);
}
if (counter_init(cnt) < 0) {
printf("Error: Counter Invalid\n");
print_usage(argv[0]);
exit(EXIT_FAILURE);
}
a = malloc(len*sizeof(*a));
b = malloc(len*sizeof(*b));
for (i = 0; i < len; ++i) {
a[i] = i+128;
b[i] = i+64;
}
page_size = sysconf(_SC_PAGESIZE);
/*Allocate memory for the page size */
addr = mmap(NULL, page_size, PROT_READ, MAP_SHARED, fddev, 0);
if (addr == (void *)(-1)) {
printf("Error: mmap() syscall returned with (%s)\n",
strerror(errno));
print_usage(argv[0]);
exit(EXIT_FAILURE);
}
i = 0;
start_count = stop_count = 0;
/* --------------------Critical section-------------- */
start_count = mmap_read_self(addr);
for (i = 0; i < 1000; i++) {
sum = loop(a, b, len);
mmap_read_self(addr);
}
stop_count = mmap_read_self(addr);
/* --------------------End Critical section-------------- */
pre_loop_res = abs(stop_count-start_count)/1000;
printf("\nsum=%d Avg count [ Loop + Read ] = %ld\n", sum,
pre_loop_res);
start_count = stop_count = 0;
/* --------------------Critical section-------------- */
start_count = mmap_read_self(addr);
for (i = 0; i < 1000; i++)
sum = loop(a, b, len);
stop_count = mmap_read_self(addr);
/* --------------------End Critical section-------------- */
post_loop_res = abs(stop_count-start_count)/1000;
printf("sum=%d Avg count [ Loop ] = %ld\n", sum,
post_loop_res);
printf("\n--------------------------------------------------------\n");
printf("\tDelay[cpucycles]=%d\n", abs(post_loop_res - pre_loop_res));
printf("\n--------------------------------------------------------\n");
munmap(addr, page_size);
free(a);
free(b);
close(fddev);
return 0;
}
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