#11 fix to get CPU frequency on Linux

[tom zhou]

Index: src/common.cpp

--- src/common.cpp (revision 458)
+++ src/common.cpp (working copy)
@@ -43,6 +43,7 @@
#include <cstring>
#include <cerrno>
#include <unistd.h>
+ #include <stdio.h>
#ifdef OSX
#include <mach mach_time.h="">
#endif
@@ -155,6 +156,35 @@
mach_timebase_info_data_t info;
mach_timebase_info(&info);
frequency = info.denom * 1000ULL / info.numer;
+ #elif defined(LINUX)
+ // extract cpu frequency from /proc/cpuinfo
+ float mhz = 0;
+ char str[256], p = NULL;
+ int find = 0;
+ FILE * fd = fopen("/proc/cpuinfo", "r");
+
+ if (fd == NULL) {
+ perror("fopen /proc/cpuinfo");
+ } else {
+ while (fgets(str, 256, fd)) {
+ if (strncmp("cpu MHz", str, sizeof("cpu MHz")-1) == 0) {
+ find = 1;
+ break;
+ }
+ }
+ fclose(fd);
+
+ if (find) {
+ p = str;
+ while (p++ != ':');
+
+ sscanf(p, "%f", &mhz);
+ frequency = (uint64_t)mhz;
+ ///printf("linux cpu MHz: %f, %lld\n", mhz, frequency);
+ } else {
+ printf("Warning!!! /proc/cpuinfo cpu MHz unknown\n");
+ }
+ }
#endif

// Fall back to microsecond if the resolution is not high enough.