Modified source engine (2017) developed by valve and leaked in 2020. Not for commercial purporses
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//========= Copyright 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
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#include <sys/sysctl.h>
#endif
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#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; return *this; }
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 = right_us - left_us;
return diff_us * ( 1.0 / 1000000.0 );
}
timeval m_TimeVal;
};
// Compute the positive difference between two 64 bit numbers.
static inline uint64 diff(uint64 v1, uint64 v2)
{
int64 d = v1 - v2;
if (d >= 0)
return d;
else
return -d;
}
#ifdef OSX
// Mac
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
// Linux
uint64 GetCPUFreqFromPROC()
{
double mhz = 0;
char line[1024], *s, search_str[] = "cpu MHz";
/* open proc/cpuinfo */
FILE *fp = fopen( "/proc/cpuinfo", "r" );
if (fp == 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;
}
}
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
// Try to open cpuinfo_max_freq. If the kernel was built with cpu scaling support disabled, this will fail.
FILE *fp = fopen( "/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq", "r" );
if ( fp )
{
char buf[ 256 ];
uint64 retVal = 0;
buf[ 0 ] = 0;
if( fread( buf, 1, ARRAYSIZE( buf ), fp ) )
{
retVal = ( uint64 )atoll( buf );
}
fclose(fp);
if( retVal )
{
return retVal * 1000;
}
}
// 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 );
// end_time - start_time calls into the overloaded TimeVal operator- way above, and returns a double.
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;
}