[PATCH] rt-tests: oslat: convert to nanoseconds correctly

[PATCH] rt-tests: oslat: convert to nanoseconds correctly

[Marcelo Tosatti]

With buckets of size 1us, accounting for measurements in the
[1ns, 999ns] range are done to the 2us bucket (while they 
should be accounted in the 1us bucket):

    001 (us):	0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
    002 (us):	41916187 41937649 41938461 42029055 ...
    003 (us):	969 985 958 972 964 986 970 961 973 ...

Fix this by doing a plain cycles -> nanoseconds convertion:

    001 (us):	43287555 43086678 43087427 43109974 ...
    002 (us):	983 987 985 975 982 960 993 961 992 ...
    003 (us):	9 6 7 13 9 22 3 21 3 3 8 8 10 11 3 55


Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Reported-by: Chuck Newman <chuck.newman@hpe.com>

diff --git a/src/oslat/oslat.c b/src/oslat/oslat.c
index 4bdca64..13e887d 100644
--- a/src/oslat/oslat.c
+++ b/src/oslat/oslat.c
@@ -334,7 +334,7 @@ static void insert_bucket(struct thread *t, stamp_t value)
 	uint64_t extra;
 	double us;
 
-	lat = (value * g.unit_per_us + t->counter_mhz - 1) / t->counter_mhz;
+	lat = (value * g.unit_per_us) / t->counter_mhz;
 	us = (double)lat / g.unit_per_us;
 	if (!g.preheat && g.trace_threshold && us >= g.trace_threshold) {
 		char *line = "%s: Trace threshold (%d us) triggered on cpu %d with %.*f us!\n";

Re: [PATCH] rt-tests: oslat: convert to nanoseconds correctly

[John Kacur]

On Thu, 1 Feb 2024, Marcelo Tosatti wrote:

> 
> With buckets of size 1us, accounting for measurements in the
> [1ns, 999ns] range are done to the 2us bucket (while they 
> should be accounted in the 1us bucket):
> 
>     001 (us):	0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
>     002 (us):	41916187 41937649 41938461 42029055 ...
>     003 (us):	969 985 958 972 964 986 970 961 973 ...
> 
> Fix this by doing a plain cycles -> nanoseconds convertion:
> 
>     001 (us):	43287555 43086678 43087427 43109974 ...
>     002 (us):	983 987 985 975 982 960 993 961 992 ...
>     003 (us):	9 6 7 13 9 22 3 21 3 3 8 8 10 11 3 55
> 
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> Reported-by: Chuck Newman <chuck.newman@hpe.com>
> 
> diff --git a/src/oslat/oslat.c b/src/oslat/oslat.c
> index 4bdca64..13e887d 100644
> --- a/src/oslat/oslat.c
> +++ b/src/oslat/oslat.c
> @@ -334,7 +334,7 @@ static void insert_bucket(struct thread *t, stamp_t value)
>  	uint64_t extra;
>  	double us;
>  
> -	lat = (value * g.unit_per_us + t->counter_mhz - 1) / t->counter_mhz;
> +	lat = (value * g.unit_per_us) / t->counter_mhz;
>  	us = (double)lat / g.unit_per_us;
>  	if (!g.preheat && g.trace_threshold && us >= g.trace_threshold) {
>  		char *line = "%s: Trace threshold (%d us) triggered on cpu %d with %.*f us!\n";
> 
> 
> 
Signed-off-by: John Kacur <jkacur@redhat.com>