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

[Pierre-Marc Fournier]

Thanks, comments below.


On 05/24/2010 10:54 AM, Nils Carlson wrote:
> 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;

Any specific reason for truncating the nanoseconds here?

>
>          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 \

I guess this isn't supposed to be part of the patch?

>          $(top_builddir)/snprintf/libustsnprintf.la \
>          $(top_builddir)/libustcomm/libustcomm.la
>
>
>
>
>
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