be/src/gutil/sysinfo.h

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#ifndef _SYSINFO_H_
#define _SYSINFO_H_

#include <cstdint>

namespace base {

// Return the number of online CPUs. This is computed and cached the first time this or
// NumCPUs() is called, so does not reflect any CPUs enabled or disabled at a later
// point in time.
//
// Note that, if not all CPUs are online, this may return a value lower than the maximum
// value of sched_getcpu().
extern int NumCPUs();

// Return the maximum CPU index that may be returned by sched_getcpu(). For example, on
// an 8-core machine, this will return '7' even if some of the CPUs have been disabled.
extern int MaxCPUIndex();

void SleepForNanoseconds(int64_t nanoseconds);
void SleepForMilliseconds(int64_t milliseconds);

// processor cycles per second of each processor.  Thread-safe.
extern double CyclesPerSecond(void);

// Parse the maximum CPU index from 'str'. The list is in the format of the CPU lists
// under /sys/devices/system/cpu/, e.g. /sys/devices/system/cpu/present. Returns the
// index of the max CPU or -1 if the string could not be parsed.
// Examples of the format and the expected output include:
// * "0\n" -> 0
// * "0-8\n" -> 8
// * "0-15,32-47\n" -> 47
// * "2,4-127,128-143\n" -> 143
// Ref: https://www.kernel.org/doc/Documentation/cputopology.txt
// Exposed for testing.
extern int ParseMaxCpuIndex(const char* str);

} // namespace base
#endif   /* #ifndef _SYSINFO_H_ */