Modified source engine (2017) developed by valve and leaked in 2020. Not for commercial purporses
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//========= Copyright 1996-2005, Valve Corporation, All rights reserved. ============//
//
// Purpose: determine CPU speed under linux
//
// $NoKeywords: $
//=============================================================================//
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#ifdef LINUX
#include <linux/sysctl.h>
#else
#include <sys/sysctl.h>
#endif
#include <sys/time.h>
#include <unistd.h>
#include <tier0/platform.h>
#include <errno.h>
#define rdtsc(x) \
__asm__ __volatile__ ("rdtsc" : "=A" (x))
class TimeVal
{
public:
TimeVal() {}
TimeVal& operator=(const TimeVal &val) { m_TimeVal = val.m_TimeVal; }
inline double operator-(const TimeVal &left)
{
uint64 left_us = (uint64) left.m_TimeVal.tv_sec * 1000000 + left.m_TimeVal.tv_usec;
uint64 right_us = (uint64) m_TimeVal.tv_sec * 1000000 + m_TimeVal.tv_usec;
uint64 diff_us = left_us - right_us;
return diff_us/1000000;
}
timeval m_TimeVal;
};
// Compute the positive difference between two 64 bit numbers.
static inline uint64 diff(uint64 v1, uint64 v2)
{
uint64 d = v1 - v2;
if (d >= 0) return d; else return -d;
}
#ifdef OSX
uint64 GetCPUFreqFromPROC()
{
int mib[2] = {CTL_HW, HW_CPU_FREQ};
uint64 frequency = 0;
size_t len = sizeof(frequency);
if (sysctl(mib, 2, &frequency, &len, NULL, 0) == -1)
return 0;
return frequency;
}
#else
uint64 GetCPUFreqFromPROC()
{
double mhz = 0;
char line[1024], *s, search_str[] = "cpu MHz";
FILE *fp;
/* open proc/cpuinfo */
if ((fp = fopen("/proc/cpuinfo", "r")) == NULL)
{
return 0;
}
/* ignore all lines until we reach MHz information */
while (fgets(line, 1024, fp) != NULL)
{
if (strstr(line, search_str) != NULL)
{
/* ignore all characters in line up to : */
for (s = line; *s && (*s != ':'); ++s);
/* get MHz number */
if (*s && (sscanf(s+1, "%lf", &mhz) == 1))
break;
}
}
if (fp!=NULL) fclose(fp);
return (uint64)(mhz*1000000);
}
#endif
uint64 CalculateCPUFreq()
{
#ifdef LINUX
char const *pFreq = getenv("CPU_MHZ");
if ( pFreq )
{
uint64 retVal = 1000000;
return retVal * atoi( pFreq );
}
#endif
// Compute the period. Loop until we get 3 consecutive periods that
// are the same to within a small error. The error is chosen
// to be +/- 0.02% on a P-200.
const uint64 error = 40000;
const int max_iterations = 600;
int count;
uint64 period, period1 = error * 2, period2 = 0, period3 = 0;
for (count = 0; count < max_iterations; count++)
{
TimeVal start_time, end_time;
uint64 start_tsc, end_tsc;
gettimeofday (&start_time.m_TimeVal, 0);
rdtsc (start_tsc);
usleep (5000); // sleep for 5 msec
gettimeofday (&end_time.m_TimeVal, 0);
rdtsc (end_tsc);
period3 = (end_tsc - start_tsc) / (end_time - start_time);
if (diff (period1, period2) <= error &&
diff (period2, period3) <= error &&
diff (period1, period3) <= error)
break;
period1 = period2;
period2 = period3;
}
if (count == max_iterations)
{
return GetCPUFreqFromPROC(); // fall back to /proc
}
// Set the period to the average period measured.
period = (period1 + period2 + period3) / 3;
// Some Pentiums have broken TSCs that increment very
// slowly or unevenly.
if (period < 10000000)
{
return GetCPUFreqFromPROC(); // fall back to /proc
}
return period;
}