Reland "Linux perf tool support update + refactoring." (r22146, attempt #5)

src/base/platform/time.cc

Index: src/base/platform/time.cc
diff --git a/src/base/platform/time.cc b/src/base/platform/time.cc
index f3442b51bdf79132bc37949efee573dadb7480b4..f8ff893288008a2d55cb60585803b6514fb5f2dc 100644
--- a/src/base/platform/time.cc
+++ b/src/base/platform/time.cc
@@ -5,6 +5,7 @@
 #include "src/base/platform/time.h"
 
 #if V8_OS_POSIX
+#include <fcntl.h>  // for O_RDONLY
 #include <sys/time.h>
 #endif
 #if V8_OS_MACOSX
@@ -516,6 +517,14 @@ bool TimeTicks::IsHighResolutionClockWorking() {
   return high_res_tick_clock.Pointer()->IsHighResolution();
 }
 
+
+// static
+TimeTicks TimeTicks::KernelTimestampNow() { return TimeTicks(0); }
+
+
+// static
+bool TimeTicks::KernelTimestampAvailable() { return false; }
+
 #else  // V8_OS_WIN
 
 TimeTicks TimeTicks::Now() {
@@ -563,6 +572,82 @@ bool TimeTicks::IsHighResolutionClockWorking() {
   return true;
 }
 
+
+#if V8_OS_LINUX && !V8_LIBRT_NOT_AVAILABLE
+
+class KernelTimestampClock {
+ public:
+  KernelTimestampClock() : clock_fd_(-1), clock_id_(kClockInvalid) {
+    clock_fd_ = open(kTraceClockDevice, O_RDONLY);
+    if (clock_fd_ == -1) {
+      return;
+    }
+    clock_id_ = get_clockid(clock_fd_);
+  }
+
+  virtual ~KernelTimestampClock() {
+    if (clock_fd_ != -1) {
+      close(clock_fd_);
+    }
+  }
+
+  int64_t Now() {
+    if (clock_id_ == kClockInvalid) {
+      return 0;
+    }
+
+    struct timespec ts;
+
+    clock_gettime(clock_id_, &ts);
+    return ((int64_t)ts.tv_sec * kNsecPerSec) + ts.tv_nsec;
+  }
+
+  bool Available() { return clock_id_ != kClockInvalid; }
+
+ private:
+  static const clockid_t kClockInvalid = -1;
+  static const char kTraceClockDevice[];
+  static const uint64_t kNsecPerSec = 1000000000;
+
+  int clock_fd_;
+  clockid_t clock_id_;
+
+  static int get_clockid(int fd) { return ((~(clockid_t)(fd) << 3) | 3); }
+};
+
+
+// Timestamp module name
+const char KernelTimestampClock::kTraceClockDevice[] = "/dev/trace_clock";
+
+#else
+
+class KernelTimestampClock {
+ public:
+  KernelTimestampClock() {}
+
+  int64_t Now() { return 0; }
+  bool Available() { return false; }
+};
+
+#endif  // V8_OS_LINUX && !V8_LIBRT_NOT_AVAILABLE
+
+static LazyStaticInstance<KernelTimestampClock,
+                          DefaultConstructTrait<KernelTimestampClock>,
+                          ThreadSafeInitOnceTrait>::type kernel_tick_clock =
+    LAZY_STATIC_INSTANCE_INITIALIZER;
+
+
+// static
+TimeTicks TimeTicks::KernelTimestampNow() {
+  return TimeTicks(kernel_tick_clock.Pointer()->Now());
+}
+
+
+// static
+bool TimeTicks::KernelTimestampAvailable() {
+  return kernel_tick_clock.Pointer()->Available();
+}
+
 #endif  // V8_OS_WIN
 
 } }  // namespace v8::base