// ---------------------------------------------------------------------- // CycleClock // A CycleClock tells you the current time in Cycles. The "time" // is actually time since power-on. This is like time() but doesn't // involve a system call and is much more precise. // // NOTE: Not all cpu/platform/kernel combinations guarantee that this // clock increments at a constant rate or is synchronized across all logical // cpus in a system. // // If you need the above guarantees, please consider using a different // API. There are efforts to provide an interface which provides a millisecond // granularity and implemented as a memory read. A memory read is generally // cheaper than the CycleClock for many architectures. // // Also, in some out of order CPU implementations, the CycleClock is not // serializing. So if you're trying to count at cycles granularity, your // data might be inaccurate due to out of order instruction execution. // ---------------------------------------------------------------------- #ifndef BENCHMARK_CYCLECLOCK_H_ #define BENCHMARK_CYCLECLOCK_H_ #include <cstdint> #include "benchmark/macros.h" #include "internal_macros.h" #if defined(BENCHMARK_OS_MACOSX) #include <mach/mach_time.h> #endif // For MSVC, we want to use '_asm rdtsc' when possible (since it works // with even ancient MSVC compilers), and when not possible the // __rdtsc intrinsic, declared in <intrin.h>. Unfortunately, in some // environments, <windows.h> and <intrin.h> have conflicting // declarations of some other intrinsics, breaking compilation. // Therefore, we simply declare __rdtsc ourselves. See also // http://connect.microsoft.com/VisualStudio/feedback/details/262047 #if defined(COMPILER_MSVC) && !defined(_M_IX86) extern "C" uint64_t __rdtsc(); #pragma intrinsic(__rdtsc) #endif #ifndef BENCHMARK_OS_WINDOWS #include <sys/time.h> #endif namespace benchmark { // NOTE: only i386 and x86_64 have been well tested. // PPC, sparc, alpha, and ia64 are based on // http://peter.kuscsik.com/wordpress/?p=14 // with modifications by m3b. See also // https://setisvn.ssl.berkeley.edu/svn/lib/fftw-3.0.1/kernel/cycle.h namespace cycleclock { // This should return the number of cycles since power-on. Thread-safe. inline BENCHMARK_ALWAYS_INLINE int64_t Now() { #if defined(BENCHMARK_OS_MACOSX) // this goes at the top because we need ALL Macs, regardless of // architecture, to return the number of "mach time units" that // have passed since startup. See sysinfo.cc where // InitializeSystemInfo() sets the supposed cpu clock frequency of // macs to the number of mach time units per second, not actual // CPU clock frequency (which can change in the face of CPU // frequency scaling). Also note that when the Mac sleeps, this // counter pauses; it does not continue counting, nor does it // reset to zero. return mach_absolute_time(); #elif defined(__i386__) int64_t ret; __asm__ volatile("rdtsc" : "=A"(ret)); return ret; #elif defined(__x86_64__) || defined(__amd64__) uint64_t low, high; __asm__ volatile("rdtsc" : "=a"(low), "=d"(high)); return (high << 32) | low; #elif defined(__powerpc__) || defined(__ppc__) // This returns a time-base, which is not always precisely a cycle-count. int64_t tbl, tbu0, tbu1; asm("mftbu %0" : "=r"(tbu0)); asm("mftb %0" : "=r"(tbl)); asm("mftbu %0" : "=r"(tbu1)); tbl &= -static_cast<int64>(tbu0 == tbu1); // high 32 bits in tbu1; low 32 bits in tbl (tbu0 is garbage) return (tbu1 << 32) | tbl; #elif defined(__sparc__) int64_t tick; asm(".byte 0x83, 0x41, 0x00, 0x00"); asm("mov %%g1, %0" : "=r"(tick)); return tick; #elif defined(__ia64__) int64_t itc; asm("mov %0 = ar.itc" : "=r"(itc)); return itc; #elif defined(COMPILER_MSVC) && defined(_M_IX86) // Older MSVC compilers (like 7.x) don't seem to support the // __rdtsc intrinsic properly, so I prefer to use _asm instead // when I know it will work. Otherwise, I'll use __rdtsc and hope // the code is being compiled with a non-ancient compiler. _asm rdtsc #elif defined(COMPILER_MSVC) return __rdtsc(); #elif defined(__aarch64__) // System timer of ARMv8 runs at a different frequency than the CPU's. // The frequency is fixed, typically in the range 1-50MHz. It can be // read at CNTFRQ special register. We assume the OS has set up // the virtual timer properly. int64_t virtual_timer_value; asm volatile("mrs %0, cntvct_el0" : "=r"(virtual_timer_value)); return virtual_timer_value; #elif defined(__ARM_ARCH) #if (__ARM_ARCH >= 6) // V6 is the earliest arch that has a standard cyclecount uint32_t pmccntr; uint32_t pmuseren; uint32_t pmcntenset; // Read the user mode perf monitor counter access permissions. asm("mrc p15, 0, %0, c9, c14, 0" : "=r"(pmuseren)); if (pmuseren & 1) { // Allows reading perfmon counters for user mode code. asm("mrc p15, 0, %0, c9, c12, 1" : "=r"(pmcntenset)); if (pmcntenset & 0x80000000ul) { // Is it counting? asm("mrc p15, 0, %0, c9, c13, 0" : "=r"(pmccntr)); // The counter is set up to count every 64th cycle return static_cast<int64_t>(pmccntr) * 64; // Should optimize to << 6 } } #endif struct timeval tv; gettimeofday(&tv, nullptr); return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec; #elif defined(__mips__) // mips apparently only allows rdtsc for superusers, so we fall // back to gettimeofday. It's possible clock_gettime would be better. struct timeval tv; gettimeofday(&tv, nullptr); return static_cast<int64_t>(tv.tv_sec) * 1000000 + tv.tv_usec; #else // The soft failover to a generic implementation is automatic only for ARM. // For other platforms the developer is expected to make an attempt to create // a fast implementation and use generic version if nothing better is available. #error You need to define CycleTimer for your OS and CPU #endif } } // end namespace cycleclock } // end namespace benchmark #endif // BENCHMARK_CYCLECLOCK_H_