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Remove tunable estimate for cycles per second

This commit is contained in:
Dominic Hamon 2014-01-08 09:11:07 -08:00
parent 9d230ffb47
commit dc5b533adb
1 changed files with 10 additions and 13 deletions
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23
src/sysinfo.cc
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@ -20,21 +20,18 @@
namespace benchmark {
namespace {
const int64_t estimate_time_ms = 1000;
pthread_once_t cpuinfo_init = PTHREAD_ONCE_INIT;
double cpuinfo_cycles_per_second = 1.0;
int cpuinfo_num_cpus = 1; // Conservative guess
static pthread_mutex_t cputimens_mutex;
pthread_mutex_t cputimens_mutex;
// Helper function estimates cycles/sec by observing cycles elapsed during
// sleep(). Using small sleep time decreases accuracy significantly.
int64_t EstimateCyclesPerSecond(const int estimate_time_ms) {
CHECK(estimate_time_ms > 0);
double multiplier = 1000.0 / (double)estimate_time_ms; // scale by this much
int64_t EstimateCyclesPerSecond() {
const int64_t start_ticks = cycleclock::Now();
SleepForMilliseconds(estimate_time_ms);
const int64_t guess = int64_t(multiplier * (cycleclock::Now() - start_ticks));
return guess;
return cycleclock::Now() - start_ticks;
}
// Helper function for reading an int from a file. Returns true if successful
@ -99,9 +96,9 @@ void InitializeSystemInfo() {
if (fd == -1) {
perror(pname);
if (!saw_mhz) {
cpuinfo_cycles_per_second = EstimateCyclesPerSecond(1000);
cpuinfo_cycles_per_second = EstimateCyclesPerSecond();
}
return; // TODO: use generic tester instead?
return;
}
double bogo_clock = 1.0;
@ -166,7 +163,7 @@ void InitializeSystemInfo() {
cpuinfo_cycles_per_second = bogo_clock;
} else {
// If we don't even have bogomips, we'll use the slow estimation.
cpuinfo_cycles_per_second = EstimateCyclesPerSecond(1000);
cpuinfo_cycles_per_second = EstimateCyclesPerSecond();
}
}
if (num_cpus == 0) {
@ -202,7 +199,7 @@ void InitializeSystemInfo() {
if ( sysctlbyname(sysctl_path, &hz, &sz, NULL, 0) != 0 ) {
fprintf(stderr, "Unable to determine clock rate from sysctl: %s: %s\n",
sysctl_path, strerror(errno));
cpuinfo_cycles_per_second = EstimateCyclesPerSecond(1000);
cpuinfo_cycles_per_second = EstimateCyclesPerSecond();
} else {
cpuinfo_cycles_per_second = hz;
}
@ -222,7 +219,7 @@ void InitializeSystemInfo() {
"~MHz", NULL, &data, &data_size)))
cpuinfo_cycles_per_second = (int64)data * (int64)(1000 * 1000); // was mhz
else
cpuinfo_cycles_per_second = EstimateCyclesPerSecond(500); // TODO <500?
cpuinfo_cycles_per_second = EstimateCyclesPerSecond();
// TODO: also figure out cpuinfo_num_cpus
#elif defined OS_MACOSX
@ -251,7 +248,7 @@ void InitializeSystemInfo() {
#else
// Generic cycles per second counter
cpuinfo_cycles_per_second = EstimateCyclesPerSecond(1000);
cpuinfo_cycles_per_second = EstimateCyclesPerSecond();
#endif
}
} // end namespace