src/bench/perf.cpp

   1 // Copyright (c) 2016 The Bitcoin Core developers
   2 // Distributed under the MIT software license, see the accompanying
   3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4
   5 #include "perf.h"
   6
   7 #if defined(__i386__) || defined(__x86_64__)
   8
   9 /* These architectures support querying the cycle counter
  10  * from user space, no need for any syscall overhead.
  11  */
  12 void perf_init(void) { }
  13 void perf_fini(void) { }
  14
  15 #elif defined(__linux__)
  16
  17 #include <unistd.h>
  18 #include <sys/syscall.h>
  19 #include <linux/perf_event.h>
  20
  21 static int fd = -1;
  22 static struct perf_event_attr attr;
  23
  24 void perf_init(void)
  25 {
  26     attr.type = PERF_TYPE_HARDWARE;
  27     attr.config = PERF_COUNT_HW_CPU_CYCLES;
  28     fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, 0);
  29 }
  30
  31 void perf_fini(void)
  32 {
  33     if (fd != -1) {
  34         close(fd);
  35     }
  36 }
  37
  38 uint64_t perf_cpucycles(void)
  39 {
  40     uint64_t result = 0;
  41     if (fd == -1 || read(fd, &result, sizeof(result)) < (ssize_t)sizeof(result)) {
  42         return 0;
  43     }
  44     return result;
  45 }
  46
  47 #else /* Unhandled platform */
  48
  49 void perf_init(void) { }
  50 void perf_fini(void) { }
  51 uint64_t perf_cpucycles(void) { return 0; }
  52
  53 #endif