Re: [PATCH i-g-t v6] lib/igt_core: Prefer CLOCK_MONOTONIC_RAW

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

This could be merged?

On pe, 2015-11-20 at 13:57 +0200, Joonas Lahtinen wrote:
> CLOCK_MONOTONIC_RAW is not affected by NTP, so it should be THE clock
> used for timing execution of tests.
> 
> When fetching either the starting or ending time of a test, show the
> time as -1.000s.
> 
> v6:
> - Whitespace corrections (Chris)
> 
> v5:
> - Do not use C99 style comments (Chris)
> 
> v4:
> - Introduce time_valid macro (Chris)
> - Reduce amount of boilerplate code for calculating elapsed time
> 
> v3:
> - Do not exit directly from handler (Chris)
> - Show elapsed time as -1 if it is not calculable
> 
> v2:
> - Cache the used clock (Chris)
> - Do not change the clock during execution
> - Spit out and error if monotonic time can not be read
> 
> Cc: Thomas Wood <thomas.wood@intel.com>
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> ---
>  lib/igt_core.c | 54 +++++++++++++++++++++++++++++++++++++++++-------
> ------
>  1 file changed, 41 insertions(+), 13 deletions(-)
> 
> diff --git a/lib/igt_core.c b/lib/igt_core.c
> index 04a0ab2..84cf8d2 100644
> --- a/lib/igt_core.c
> +++ b/lib/igt_core.c
> @@ -220,6 +220,7 @@ static char *run_single_subtest = NULL;
>  static bool run_single_subtest_found = false;
>  static const char *in_subtest = NULL;
>  static struct timespec subtest_time;
> +static clockid_t igt_clock = (clockid_t)-1;
>  static bool in_fixture = false;
>  static bool test_with_subtests = false;
>  static bool in_atexit_handler = false;
> @@ -337,14 +338,49 @@ static void kmsg(const char *format, ...)
>  	fclose(file);
>  }
>  
> -static void gettime(struct timespec *ts)
> +#define time_valid(ts) ((ts)->tv_sec || (ts)->tv_nsec)
> +
> +static double
> +time_elapsed(struct timespec *then,
> +	     struct timespec* now)
> +{
> +	double elapsed = -1.;
> +
> +	if (time_valid(then) && time_valid(now)) {
> +		elapsed = now->tv_sec - then->tv_sec;
> +		elapsed += (now->tv_nsec - then->tv_nsec) * 1e-9;
> +	}
> +
> +	return elapsed;
> +}
> +
> +static int gettime(struct timespec *ts)
>  {
>  	memset(ts, 0, sizeof(*ts));
> +	errno = 0;
>  
> +	/* Stay on the same clock for consistency. */
> +	if (igt_clock != (clockid_t)-1) {
> +		if (clock_gettime(igt_clock, ts))
> +			goto error;
> +		return 0;
> +	}
> +
> +#ifdef CLOCK_MONOTONIC_RAW
> +	if (!clock_gettime(igt_clock = CLOCK_MONOTONIC_RAW, ts))
> +		return 0;
> +#endif
>  #ifdef CLOCK_MONOTONIC_COARSE
> -	if (clock_gettime(CLOCK_MONOTONIC_COARSE, ts))
> +	if (!clock_gettime(igt_clock = CLOCK_MONOTONIC_COARSE, ts))
> +		return 0;
>  #endif
> -		clock_gettime(CLOCK_MONOTONIC, ts);
> +	if (!clock_gettime(igt_clock = CLOCK_MONOTONIC, ts))
> +		return 0;
> +error:
> +	igt_warn("Could not read monotonic time: %s\n",
> +		 strerror(errno));
> +
> +	return -errno;
>  }
>  
>  bool __igt_fixture(void)
> @@ -831,15 +867,11 @@ static void exit_subtest(const char *)
> __attribute__((noreturn));
>  static void exit_subtest(const char *result)
>  {
>  	struct timespec now;
> -	double elapsed;
>  
>  	gettime(&now);
> -	elapsed = now.tv_sec - subtest_time.tv_sec;
> -	elapsed += (now.tv_nsec - subtest_time.tv_nsec) * 1e-9;
> -
>  	printf("%sSubtest %s: %s (%.3fs)%s\n",
>  	       (!__igt_plain_output) ? "\x1b[1m" : "",
> -	       in_subtest, result, elapsed,
> +	       in_subtest, result, time_elapsed(&subtest_time,
> &now),
>  	       (!__igt_plain_output) ? "\x1b[0m" : "");
>  	fflush(stdout);
>  
> @@ -1088,12 +1120,9 @@ void igt_exit(void)
>  
>  	if (!test_with_subtests) {
>  		struct timespec now;
> -		double elapsed;
>  		const char *result;
>  
>  		gettime(&now);
> -		elapsed = now.tv_sec - subtest_time.tv_sec;
> -		elapsed += (now.tv_nsec - subtest_time.tv_nsec) * 1e
> -9;
>  
>  		switch (igt_exitcode) {
>  			case IGT_EXIT_SUCCESS:
> @@ -1109,8 +1138,7 @@ void igt_exit(void)
>  				result = "FAIL";
>  		}
>  
> -
> -		printf("%s (%.3fs)\n", result, elapsed);
> +		printf("%s (%.3fs)\n", result,
> time_elapsed(&subtest_time, &now));
>  		exit(igt_exitcode);
>  	}
>  
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation

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