178 lines
3.8 KiB
C++
178 lines
3.8 KiB
C++
//========= Copyright Valve Corporation, All rights reserved. ============//
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//
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// Purpose: determine CPU speed under linux
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//
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// $NoKeywords: $
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//=============================================================================//
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/sysctl.h>
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#include <sys/time.h>
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#include <unistd.h>
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#include <tier0/platform.h>
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#include <errno.h>
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#define rdtsc(x) \
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__asm__ __volatile__ ("rdtsc" : "=A" (x))
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class TimeVal
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{
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public:
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TimeVal() {}
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TimeVal& operator=(const TimeVal &val) { m_TimeVal = val.m_TimeVal; return *this; }
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inline double operator-(const TimeVal &left)
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{
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uint64 left_us = (uint64) left.m_TimeVal.tv_sec * 1000000 + left.m_TimeVal.tv_usec;
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uint64 right_us = (uint64) m_TimeVal.tv_sec * 1000000 + m_TimeVal.tv_usec;
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uint64 diff_us = right_us - left_us;
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return diff_us * ( 1.0 / 1000000.0 );
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}
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timeval m_TimeVal;
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};
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// Compute the positive difference between two 64 bit numbers.
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static inline uint64 diff(uint64 v1, uint64 v2)
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{
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int64 d = v1 - v2;
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if (d >= 0)
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return d;
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else
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return -d;
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}
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#ifdef OSX
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// Mac
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uint64 GetCPUFreqFromPROC()
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{
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int mib[2] = {CTL_HW, HW_CPU_FREQ};
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uint64 frequency = 0;
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size_t len = sizeof(frequency);
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if (sysctl(mib, 2, &frequency, &len, NULL, 0) == -1)
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return 0;
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return frequency;
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}
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#else
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// Linux
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uint64 GetCPUFreqFromPROC()
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{
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double mhz = 0;
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char line[1024], *s, search_str[] = "cpu MHz";
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/* open proc/cpuinfo */
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FILE *fp = fopen( "/proc/cpuinfo", "r" );
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if (fp == NULL)
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{
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return 0;
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}
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/* ignore all lines until we reach MHz information */
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while (fgets(line, 1024, fp) != NULL)
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{
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if (strstr(line, search_str) != NULL)
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{
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/* ignore all characters in line up to : */
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for (s = line; *s && (*s != ':'); ++s)
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;
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/* get MHz number */
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if ( *s && ( sscanf( s + 1, "%lf", &mhz) == 1 ) )
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break;
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}
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}
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fclose(fp);
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return ( uint64 )( mhz * 1000000 );
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}
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#endif
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uint64 CalculateCPUFreq()
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{
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#ifdef LINUX
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char const *pFreq = getenv( "CPU_MHZ" );
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if ( pFreq )
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{
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uint64 retVal = 1000000;
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return retVal * atoi( pFreq );
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}
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#endif
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// Try to open cpuinfo_max_freq. If the kernel was built with cpu scaling support disabled, this will fail.
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FILE *fp = fopen( "/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq", "r" );
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if ( fp )
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{
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char buf[ 256 ];
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uint64 retVal = 0;
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buf[ 0 ] = 0;
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if( fread( buf, 1, ARRAYSIZE( buf ), fp ) )
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{
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retVal = ( uint64 )atoll( buf );
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}
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fclose(fp);
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if( retVal )
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{
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return retVal * 1000;
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}
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}
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// Compute the period. Loop until we get 3 consecutive periods that
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// are the same to within a small error. The error is chosen
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// to be +/- 0.02% on a P-200.
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const uint64 error = 40000;
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const int max_iterations = 600;
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int count;
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uint64 period, period1 = error * 2, period2 = 0, period3 = 0;
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for (count = 0; count < max_iterations; count++)
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{
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TimeVal start_time, end_time;
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uint64 start_tsc, end_tsc;
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gettimeofday( &start_time.m_TimeVal, 0 );
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rdtsc( start_tsc );
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usleep( 5000 ); // sleep for 5 msec
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gettimeofday( &end_time.m_TimeVal, 0 );
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rdtsc( end_tsc );
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// end_time - start_time calls into the overloaded TimeVal operator- way above, and returns a double.
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period3 = ( end_tsc - start_tsc ) / ( end_time - start_time );
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if (diff ( period1, period2 ) <= error &&
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diff ( period2, period3 ) <= error &&
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diff ( period1, period3 ) <= error )
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{
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break;
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}
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period1 = period2;
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period2 = period3;
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}
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if ( count == max_iterations )
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{
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return GetCPUFreqFromPROC(); // fall back to /proc
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}
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// Set the period to the average period measured.
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period = ( period1 + period2 + period3 ) / 3;
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// Some Pentiums have broken TSCs that increment very
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// slowly or unevenly.
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if (period < 10000000)
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{
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return GetCPUFreqFromPROC(); // fall back to /proc
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}
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return period;
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}
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