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91 lines
1.9 KiB
C
91 lines
1.9 KiB
C
#include <stdio.h>
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#include <string.h>
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#include "error.h"
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#include "hwclock.h"
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static double hwtick_val;
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#define two_to_32 4294967296.0
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static double hwclock_offset;
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#if defined(__x86_64__) && defined(__GNUC__)
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#define DEFAULT_MHZ 1200.e6
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static double
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mhz_from_proc(){
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FILE *fp = fopen("/proc/cpuinfo", "r");
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char line[512];
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if( fp == NULL ){
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Warning("Can't open /proc/cpuinfo\n");
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return DEFAULT_MHZ;
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}
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while( fgets(line, sizeof(line), fp) ){
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char *m;
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int nscan;
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double mhz;
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if( (m = strstr(line, "cpu MHz")) ){
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/* sscanf should match any amount of whitespace around the : */
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nscan = sscanf(m, "cpu MHz : %lf\n", &mhz);
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if( nscan == 1 ){
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fclose(fp);
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return mhz*1.0e6;
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}else{
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Warning("sscanf returns %d, on '%s' of /proc/cpuinfo mhz line failed\n", nscan, line);
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fclose(fp);
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return DEFAULT_MHZ; /* let's just guess 200Mhz */
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}
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}
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}
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Warning("Did not find cpu MHz in /proc/cpuinfo\n");
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fclose(fp);
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return DEFAULT_MHZ;
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}
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#endif
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/* This doesn't belong here, but I can't be bothered to figure out where
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it does belong! */
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double
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hwclock(void)
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{
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#if defined(__x86_64__)
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static int init = 1;
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unsigned int counter[2];
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__asm__("rdtsc \n\t"
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"movl %%eax,%0 \n\t"
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"movl %%edx,%1 \n\t"
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: "=m" (((unsigned *)counter)[0]), "=m" (((unsigned *)counter)[1])
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:
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: "eax" , "edx");
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if (init) {
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init = 0;
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hwtick_val = 1.0/mhz_from_proc();
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hwclock_offset = hwtick_val*((double)counter[1]*two_to_32 + (double)counter[0]);
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return 0.0;
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}
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return(hwtick_val*((double)counter[1]*two_to_32 + (double)counter[0])-hwclock_offset);
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#else
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{
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struct timeval tp;
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struct timezone tzp;
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gettimeofday(&tp,&tzp);
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return ( (double) tp.tv_sec + (double) tp.tv_usec * 1.e-6 );
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}
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#endif
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}
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void
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zero_hwclock(void)
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{
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hwclock_offset += hwclock();
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}
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double
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hwtick(void)
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{
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return hwtick_val;
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}
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