m1cycles.c

// Adapted from
// https://github.com/lemire/Code-used-on-Daniel-Lemire-s-blog/blob/master/2021/03/24/

#include <dlfcn.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>

#define KPERF_LIST                                                             \
  F(int, kpc_force_all_ctrs_set, int)                                          \
  F(int, kpc_set_counting, uint32_t)                                           \
  F(int, kpc_set_thread_counting, uint32_t)                                    \
  F(int, kpc_set_config, uint32_t, void *)                                     \
  F(uint32_t, kpc_get_counter_count, uint32_t)                                 \
  F(uint32_t, kpc_get_config_count, uint32_t)                                  \
  F(int, kpc_get_thread_counters, int, unsigned int, void *)

#define F(ret, name, ...)                                                      \
  typedef ret name##proc(__VA_ARGS__);                                         \
  static name##proc *name;
KPERF_LIST
#undef F

#define CFGWORD_EL0A32EN_MASK (0x10000)
#define CFGWORD_EL0A64EN_MASK (0x20000)
#define CFGWORD_EL1EN_MASK (0x40000)
#define CFGWORD_EL3EN_MASK (0x80000)
#define CFGWORD_ALLMODES_MASK (0xf0000)

#define CPMU_NONE 0
#define CPMU_CORE_CYCLE 0x02
#define CPMU_INST_A64 0x8c
#define CPMU_INST_BRANCH 0x8d
#define CPMU_SYNC_DC_LOAD_MISS 0xbf
#define CPMU_SYNC_DC_STORE_MISS 0xc0
#define CPMU_SYNC_DTLB_MISS 0xc1
#define CPMU_SYNC_ST_HIT_YNGR_LD 0xc4
#define CPMU_SYNC_BR_ANY_MISP 0xcb
#define CPMU_FED_IC_MISS_DEM 0xd3
#define CPMU_FED_ITLB_MISS 0xd4

#define KPC_CLASS_FIXED (0)
#define KPC_CLASS_CONFIGURABLE (1)
#define KPC_CLASS_POWER (2)
#define KPC_CLASS_RAWPMU (3)
#define KPC_CLASS_FIXED_MASK (1u << KPC_CLASS_FIXED)
#define KPC_CLASS_CONFIGURABLE_MASK (1u << KPC_CLASS_CONFIGURABLE)
#define KPC_CLASS_POWER_MASK (1u << KPC_CLASS_POWER)
#define KPC_CLASS_RAWPMU_MASK (1u << KPC_CLASS_RAWPMU)

#define COUNTERS_COUNT 10
#define CONFIG_COUNT 8
#define KPC_MASK (KPC_CLASS_CONFIGURABLE_MASK | KPC_CLASS_FIXED_MASK)
uint64_t g_counters[COUNTERS_COUNT];
uint64_t g_config[COUNTERS_COUNT];

static void configure_rdtsc() {
  if (kpc_set_config(KPC_MASK, g_config)) {
    printf("kpc_set_config failed\n");
    return;
  }

  if (kpc_force_all_ctrs_set(1)) {
    printf("kpc_force_all_ctrs_set failed\n");
    return;
  }

  if (kpc_set_counting(KPC_MASK)) {
    printf("kpc_set_counting failed\n");
    return;
  }

  if (kpc_set_thread_counting(KPC_MASK)) {
    printf("kpc_set_thread_counting failed\n");
    return;
  }
}

void init_cpucycles() {
  void *kperf = dlopen(
      "/System/Library/PrivateFrameworks/kperf.framework/Versions/A/kperf",
      RTLD_LAZY);
  if (!kperf) {
    printf("kperf = %p\n", kperf);
    return;
  }
#define F(ret, name, ...)                                                      \
  name = (name##proc *)(dlsym(kperf, #name));                                  \
  if (!name) {                                                                 \
    printf("%s = %p\n", #name, (void *)name);                                  \
    return;                                                                    \
  }
  KPERF_LIST
#undef F

  if (kpc_get_counter_count(KPC_MASK) != COUNTERS_COUNT) {
    printf("wrong fixed counters count\n");
    return;
  }

  if (kpc_get_config_count(KPC_MASK) != CONFIG_COUNT) {
    printf("wrong fixed config count\n");
    return;
  }
  g_config[0] = CPMU_CORE_CYCLE | CFGWORD_EL0A64EN_MASK;
  g_config[3] = CPMU_INST_BRANCH | CFGWORD_EL0A64EN_MASK;
  g_config[4] = CPMU_SYNC_BR_ANY_MISP | CFGWORD_EL0A64EN_MASK;
  g_config[5] = CPMU_INST_A64 | CFGWORD_EL0A64EN_MASK;

  configure_rdtsc();
}

uint64_t cpucycles(void) {
  static bool warned = false;
  if (kpc_get_thread_counters(0, COUNTERS_COUNT, g_counters)) {
    if (!warned) {
      printf("kpc_get_thread_counters failed, run as sudo?\n");
      warned = true;
    }
    return 1;
  }
  // g_counters[3 + 2] gives you the number of instructions 'decoded'
  // whereas g_counters[1] might give you the number of instructions 'retired'.
  return g_counters[0 + 2];
}