[ltt-dev] PATCH [0/1]: Replace gettimeofday with clock_gettime

[nils.carlson@ludd.ltu.se (Nils Carlson)]

This patch replaces gettimeofday with clock_gettime(CLOCK_MONOTONIC,)

Signed-off-by: Nils Carlson <nils.carlson at ludd.ltu.se>

diff --git a/include/ust/clock.h b/include/ust/clock.h
index d4b6a9d..bc26d26 100644
--- a/include/ust/clock.h
+++ b/include/ust/clock.h
@@ -18,6 +18,7 @@
 #ifndef UST_CLOCK_H
 #define UST_CLOCK_H

+#include <time.h>
 #include <sys/time.h>
 #include <ust/kcompat/kcompat.h>

@@ -25,7 +26,7 @@

 /* There are two types of clocks that can be used.
    - TSC based clock
-   - gettimeofday() clock
+   - gettimeofday() clock - to guarantee monotonicity use clock_gettime

    Microbenchmarks on Linux 2.6.30 on Core2 Duo 3GHz (functions are
inlined):
      Calls (100000000) to tsc(): 4004035641 cycles or 40 cycles/call
@@ -41,13 +42,13 @@

 static __inline__ u64 trace_clock_read64(void)
 {
-       struct timeval tv;
+       struct timespec ts;
        u64 retval;

-       gettimeofday(&tv, NULL);
-       retval = tv.tv_sec;
+       clock_gettime(CLOCK_MONOTONIC, &ts);
+       retval = ts.tv_sec;
        retval *= 1000000;
-       retval += tv.tv_usec;
+       retval += ts.tv_nsec / 1000;

        return retval;
 }
diff --git a/libust/Makefile.am b/libust/Makefile.am
index 2de5857..e357ad1 100644
--- a/libust/Makefile.am
+++ b/libust/Makefile.am
@@ -27,6 +27,7 @@ libust_la_LDFLAGS = -no-undefined -version-info 0:0:0

 libust_la_LIBADD = \
        -lpthread \
+       -lrt \
        $(top_builddir)/snprintf/libustsnprintf.la \
        $(top_builddir)/libustcomm/libustcomm.la