Re: [PATCH 5/5] cyclictest: Add a timestamp of the last update

[John Kacur <jkacur@gmail.com>]

On Wed, 26 Aug 2026, Sebastian Andrzej Siewior wrote:

> Add a timestamp once the the MAX value is updated. This is useful to
> figure out when a certain value was updated and if an update occurred on
> multiple CPUs at same. The output is seconds accurate, the ns are
> stripped for now.
> 
> I'm limiting this to the the -M switch, which I am using, but there
> should be nothing wrong with using it unconditionally.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  src/cyclictest/cyclictest.c | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/src/cyclictest/cyclictest.c b/src/cyclictest/cyclictest.c
> index 1cad1bf6b929e..1c14d13b7cd80 100644
> --- a/src/cyclictest/cyclictest.c
> +++ b/src/cyclictest/cyclictest.c
> @@ -145,6 +145,7 @@ struct thread_stat {
>  	long redmax;
>  	long cycleofmax;
>  	unsigned long smi_count;
> +	struct timespec max_update_ts;
>  };
>  
>  static pthread_mutex_t trigger_lock;
> @@ -834,8 +835,10 @@ static void *timerthread(void *param)
>  			stat->min = diff;
>  		if (diff > stat->max) {
>  			stat->max = diff;
> -			if (refresh_on_max)
> +			if (refresh_on_max) {
>  				need_refresh_max = true;
> +				clock_gettime(CLOCK_REALTIME, &stat->max_update_ts);
> +			}
>  		}
>  		if (need_refresh_max) {
>  			if (!pthread_mutex_trylock(&refresh_on_max_lock)) {
> @@ -1599,6 +1602,18 @@ static void print_stat(FILE *fp, struct thread_param *par, int index, int verbos
>  				stat->act, stat->cycles ?
>  				(long)(stat->avg/stat->cycles) : 0, stat->max);
>  
> +			if (refresh_on_max) {
> +				char ts_str[64];
> +				struct tm tm;
> +				time_t ts;
> +
> +				ts = stat->max_update_ts.tv_sec;
> +				localtime_r(&ts, &tm);
> +				/* RFC 2822-compliant date format */
> +				strftime(ts_str, sizeof(ts_str), "%a, %d %b %Y %T %z", &tm);

This creates a really long line with redundant information, for example

T: 0 (36716) P: 0 I:1000 C:   1331 Min:      1 Act:    2 Avg:   12 Max:      
71 Fri, 28 Aug 2026 10:18:32 -0400
T: 1 (36717) P: 0 I:1500 C:    887 Min:      1 Act:    2 Avg:   10 Max:      
62 Fri, 28 Aug 2026 10:18:32 -0400
T: 2 (36718) P: 0 I:2000 C:    665 Min:      1 Act:    2 Avg:   28 Max:      
56 Fri, 28 Aug 2026 10:18:32 -0400
T: 3 (36719) P: 0 I:2500 C:    532 Min:      1 Act:   52 Avg:   36 Max:      
57 Fri, 28 Aug 2026 10:18:32 -0400
T: 4 (36720) P: 0 I:3000 C:    443 Min:      1 Act:   51 Avg:   21 Max:      
55 Fri, 28 Aug 2026 10:18:32 -0400
T: 5 (36721) P: 0 I:3500 C:    380 Min:      1 Act:    2 Avg:    1 Max:      
12 Fri, 28 Aug 2026 10:18:32 -0400
T: 6 (36722) P: 0 I:4000 C:    332 Min:      1 Act:   52 Avg:   49 Max:      
62 Fri, 28 Aug 2026 10:18:32 -0400

Why not strftime(ts_str, sizeof(ts_str), "%T", &tm);
This will still go over 80 char, but it's more succinct.


T: 0 (40468) P: 0 I:1000 C:    282 Min:      1 Act:   52 Avg:   17 Max:      
65 10:25:32
T: 1 (40469) P: 0 I:1500 C:    188 Min:      1 Act:   51 Avg:   22 Max:      
56 10:25:31
T: 2 (40470) P: 0 I:2000 C:    141 Min:      1 Act:    2 Avg:    7 Max:      
55 10:25:31
T: 3 (40471) P: 0 I:2500 C:    113 Min:      1 Act:   63 Avg:   19 Max:      
63 10:25:32
T: 4 (40472) P: 0 I:3000 C:     94 Min:      1 Act:   52 Avg:   27 Max:      
54 10:25:31
T: 5 (40473) P: 0 I:3500 C:     80 Min:      1 Act:    5 Avg:   43 Max:      
56 10:25:32
T: 6 (40474) P: 0 I:4000 C:     70 Min:      1 Act:   51 Avg:   27 Max:      
55 10:25:32

The other patches in this series look fine.

John