[kudu] 05/07: KUDU-3029 Define CycleClock::Now for aarch64

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commit f9304fddcdf96f27d4f9c9895efb7487afaca6e5
Author: huangtianhua <hu...@gmail.com>
AuthorDate: Thu Dec 19 06:48:52 2019 +0000

    KUDU-3029 Define CycleClock::Now for aarch64
    
    System timer of ARMv8 runs at a different frequency than the CPU's.
    Add definition of CycleClock::Now to support aarch64.
    
    Change-Id: If389e6faf3899ac33bf9e954fe9c4f6b909227da
    Reviewed-on: http://gerrit.cloudera.org:8080/14929
    Reviewed-by: Adar Dembo <ad...@cloudera.com>
    Tested-by: Kudu Jenkins
---
 src/kudu/gutil/cycleclock-inl.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/kudu/gutil/cycleclock-inl.h b/src/kudu/gutil/cycleclock-inl.h
index 7738592..c913d51 100644
--- a/src/kudu/gutil/cycleclock-inl.h
+++ b/src/kudu/gutil/cycleclock-inl.h
@@ -192,6 +192,18 @@ inline int64 CycleClock::Now() {
 }
 
 // ----------------------------------------------------------------
+#elif defined(__aarch64__)
+#include "kudu/gutil/sysinfo.h"
+inline int64 CycleClock::Now() {
+  // 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;
+}
+// ----------------------------------------------------------------
 #else
 // The soft failover to a generic implementation is automatic only for some
 // platforms.  For other platforms the developer is expected to make an attempt