cputimeget opt

src/butil/time.cpp

@@ -153,6 +153,18 @@ int64_t read_invariant_cpu_frequency() {
 }
 
 int64_t invariant_cpu_freq = -1;
+
+static void __attribute__((constructor)) init_invariant_cpu_freq() {
+    int64_t baseFreq = -1;
+#if defined(__aarch64__)
+    __asm__ __volatile__("mrs %0, CNTFRQ_EL0" : "=r"(baseFreq));
+#else
+    baseFreq = detail::read_invariant_cpu_frequency();
+#enfif
+
+    detail::invariant_cpu_freq = baseFreq;
+}
+
 }  // namespace detail
 
 }  // namespace butil

src/butil/time.h

@@ -279,7 +279,7 @@ extern int64_t invariant_cpu_freq;
 // note: Inlining shortens time cost per-call for 15ns in a loop of many
 //       calls to this function.
 inline int64_t cpuwide_time_ns() {
-#if !defined(BAIDU_INTERNAL)
+#if !defined(BAIDU_INTERNAL) && !defined(__aarch64__)
     // nearly impossible to get the correct invariant cpu frequency on
     // different CPU and machines. CPU-ID rarely works and frequencies
     // in "model name" and "cpu Mhz" are both unreliable.
@@ -301,11 +301,6 @@ inline int64_t cpuwide_time_ns() {
     } else if (!cpu_freq) {
         // Lack of necessary features, return system-wide monotonic time instead.
         return monotonic_time_ns();
-    } else {
-        // Use a thread-unsafe method(OK to us) to initialize the freq
-        // to save a "if" test comparing to using a local static variable
-        detail::invariant_cpu_freq = detail::read_invariant_cpu_frequency();
-        return cpuwide_time_ns();
     }
 #endif // defined(BAIDU_INTERNAL)
 }