[PATCH rt-tests] cyclictest: finish removal of 1 second first loops

[PATCH rt-tests] cyclictest: finish removal of 1 second first loops

[Paul Gortmaker]

From: Jim Somerville <Jim.Somerville@windriver.com>

Huge latencies are observed (close to 1 second) when certain
options are used in cyclictest.

The problem was 1st introduced at commit da4956cbcaf7945554f
("use interval on first loop instead of 1 second").  It removed
the 1 second first timing loop out of the main path in cyclictest
but left it in two other paths, namely the ones triggered by
these two options:

    -r   --relative    use relative timer instead of absolute
    -s   --system      use sys_nanosleep and sys_setitimer

which in turn causes the huge latencies of close to 1 second to
be reported by cyclictest with certain uses of those two options.

Here we extend the original commit to remove the 1 second
hardcoded timer values from the RELTIME and ITIMER options, by
simply using the actual interval provided instead.

Signed-off-by: Jim Somerville <Jim.Somerville@windriver.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/src/cyclictest/cyclictest.c b/src/cyclictest/cyclictest.c
index abf3e8b..8c93ccb 100644
--- a/src/cyclictest/cyclictest.c
+++ b/src/cyclictest/cyclictest.c
@@ -775,17 +775,15 @@ void *timerthread(void *param)
 		if (par->timermode == TIMER_ABSTIME)
 			tspec.it_value = next;
 		else {
-			tspec.it_value.tv_nsec = 0;
-			tspec.it_value.tv_sec = 1;
+			tspec.it_value = interval;
 		}
 		timer_settime(timer, par->timermode, &tspec, NULL);
 	}
 
 	if (par->mode == MODE_SYS_ITIMER) {
-		itimer.it_value.tv_sec = 1;
-		itimer.it_value.tv_usec = 0;
 		itimer.it_interval.tv_sec = interval.tv_sec;
 		itimer.it_interval.tv_usec = interval.tv_nsec / 1000;
+		itimer.it_value = itimer.it_interval;
 		setitimer (ITIMER_REAL, &itimer, NULL);
 	}
 
-- 
1.8.1.2

Re: [PATCH rt-tests] cyclictest: finish removal of 1 second first loops

[John Kacur]

On Thu, 14 Feb 2013, Paul Gortmaker wrote:

> From: Jim Somerville <Jim.Somerville@windriver.com>
> 
> Huge latencies are observed (close to 1 second) when certain
> options are used in cyclictest.
> 
> The problem was 1st introduced at commit da4956cbcaf7945554f
> ("use interval on first loop instead of 1 second").  It removed
> the 1 second first timing loop out of the main path in cyclictest
> but left it in two other paths, namely the ones triggered by
> these two options:
> 
>     -r   --relative    use relative timer instead of absolute
>     -s   --system      use sys_nanosleep and sys_setitimer
> 
> which in turn causes the huge latencies of close to 1 second to
> be reported by cyclictest with certain uses of those two options.
> 
> Here we extend the original commit to remove the 1 second
> hardcoded timer values from the RELTIME and ITIMER options, by
> simply using the actual interval provided instead.
> 
> Signed-off-by: Jim Somerville <Jim.Somerville@windriver.com>
> Cc: Clark Williams <williams@redhat.com>
> Cc: John Kacur <jkacur@redhat.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
> 
> diff --git a/src/cyclictest/cyclictest.c b/src/cyclictest/cyclictest.c
> index abf3e8b..8c93ccb 100644
> --- a/src/cyclictest/cyclictest.c
> +++ b/src/cyclictest/cyclictest.c
> @@ -775,17 +775,15 @@ void *timerthread(void *param)
>  		if (par->timermode == TIMER_ABSTIME)
>  			tspec.it_value = next;
>  		else {
> -			tspec.it_value.tv_nsec = 0;
> -			tspec.it_value.tv_sec = 1;
> +			tspec.it_value = interval;
>  		}
>  		timer_settime(timer, par->timermode, &tspec, NULL);
>  	}
>  
>  	if (par->mode == MODE_SYS_ITIMER) {
> -		itimer.it_value.tv_sec = 1;
> -		itimer.it_value.tv_usec = 0;
>  		itimer.it_interval.tv_sec = interval.tv_sec;
>  		itimer.it_interval.tv_usec = interval.tv_nsec / 1000;
> +		itimer.it_value = itimer.it_interval;
>  		setitimer (ITIMER_REAL, &itimer, NULL);
>  	}
>  
> -- 

Thanks Jim and Paul, I've added it to my queue for the next build.

John