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// Copyright (c) 2016 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include "perf.h"
#if defined(__i386__) || defined(__x86_64__)
/* These architectures support querying the cycle counter
* from user space, no need for any syscall overhead.
*/
void perf_init(void) { }
void perf_fini(void) { }
#elif defined(__linux__)
#include <unistd.h>
#include <sys/syscall.h>
#include <linux/perf_event.h>
static int fd = -1;
static struct perf_event_attr attr;
void perf_init(void)
{
attr.type = PERF_TYPE_HARDWARE;
attr.config = PERF_COUNT_HW_CPU_CYCLES;
fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);
}
void perf_fini(void)
{
if (fd != -1) {
close(fd);
}
}
uint64_t perf_cpucycles(void)
{
uint64_t result = 0;
if (fd == -1 || read(fd, &result, sizeof(result)) < (ssize_t)sizeof(result)) {
return 0;
}
return result;
}
#else /* Unhandled platform */
void perf_init(void) { }
void perf_fini(void) { }
uint64_t perf_cpucycles(void) { return 0; }
#endif