Re: [Xenomai-core] measuring tasks execution time

[Jan Kiszka <jan.kiszka@domain.hid>]

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Daniel Simon wrote:
> On Sun, 08 Jul 2007 12:11:56 +0200
> Jan Kiszka <jan.kiszka@domain.hid> wrote:
> 
> Hello,
>> You are welcome to test, fix, improve, or just use it. Looking forward
>> to your feedback!
> 
> here are attached some corrections against your previous patch (itself against
> #2758 files): from my tests I now get likely exectime values from both remote
> and self measurement (i.e. we get the accumulated exectime at the instant we
> call rt_task_inquire ), and the stats given in /proc still seem to behave
> normally...
> 
> the full patch against the original 2758 version is also given in attachement

To check if I got it the first attachment is an add-on patch, the second
one is the base patch as in my repos + the former add-on patch?

Then let's comment on the add-on:

> diff -urN xenomai-2758/include/nucleus/stat.h xenomai-2758-V2/include/nucleus/stat.h
> --- xenomai-2758/include/nucleus/stat.h	2007-07-11 15:16:14.000000000 +0200
> +++ xenomai-2758-V2/include/nucleus/stat.h	2007-07-11 15:09:38.000000000 +0200
> @@ -42,7 +42,7 @@
>  do { \
>  	(sched)->current_account->total += \
>  		date - (sched)->last_account_switch; \
> -	(sched)->last_account_switch = date; \
> +	(sched)->last_account_switch = (sched)->current_account->start = date; \

That looks bogus on first sight, but I might miss your intention.
current_account points to the overall stats of an accounted entity.
Therefore, start must always contain the start time, not the last switch
time. Please explain your idea.

>  	/* All changes must be committed before changing the current_account \
>  	   reference in sched (required for xnintr_sync_stat_references) */ \
>  	xnarch_memory_barrier(); \
> @@ -71,6 +71,9 @@
>  #define xnstat_runtime_get_start(account)	((account)->start)
>  #define xnstat_runtime_get_total(account)	((account)->total)
>  
> +/* Obtain last time something has been switched */
> +#define xnstat_runtime_get_last_switch(sched)	((sched)->last_account_switch)
> +

OK (though a more precise comment would be good :))

>  /* Reset statistics from inside the accounted entity (e.g. after CPU
>     migration). */
>  #define xnstat_runtime_reset_stats(stat) \
> @@ -113,6 +116,7 @@
>  #define xnstat_runtime_finalize(sched, new_account)		do { } while (0)
>  #define xnstat_runtime_get_start(account)			({ 0; })
>  #define xnstat_runtime_get_total(account)			({ 0; })
> +#define xnstat_runtime_get_last_switch(sched)			({ 0; })
>  #define xnstat_runtime_reset_stats(account)			do { } while (0)
>  
>  typedef struct xnstat_counter {
> diff -urN xenomai-2758/include/nucleus/thread.h xenomai-2758-V2/include/nucleus/thread.h
> --- xenomai-2758/include/nucleus/thread.h	2007-07-11 15:16:14.000000000 +0200
> +++ xenomai-2758-V2/include/nucleus/thread.h	2007-07-11 14:28:15.000000000 +0200
> @@ -294,7 +294,7 @@
>  #define xnthread_affinity(thread)          ((thread)->affinity)
>  #define xnthread_affine_p(thread, cpu)     xnarch_cpu_isset(cpu, (thread)->affinity)
>  #define xnthread_get_exectime(thread)      xnstat_runtime_get_total(&(thread)->stat.account)
> -#define xnthread_get_lastswitch(thread)    xnstat_runtime_get_start(&(thread)->stat.account)
> +#define xnthread_get_lastswitch(thread)    xnstat_runtime_get_last_switch((thread)->sched)

Yeah, that was wrong. Did your first patch hunk relate to an initial
attempt to fix this bug?

>  
>  /* Class-level operations for threads. */
>  static inline int xnthread_get_denormalized_prio(xnthread_t *t)
> diff -urN xenomai-2758/ksrc/skins/native/task.c xenomai-2758-V2/ksrc/skins/native/task.c
> --- xenomai-2758/ksrc/skins/native/task.c	2007-07-11 15:16:14.000000000 +0200
> +++ xenomai-2758-V2/ksrc/skins/native/task.c	2007-07-11 15:22:10.000000000 +0200
> @@ -1144,10 +1144,13 @@
>  	info->cprio = xnthread_current_priority(&task->thread_base);
>  	info->status = xnthread_state_flags(&task->thread_base);
>  	info->relpoint = xntimer_get_date(&task->thread_base.ptimer);
> +	if(task == xeno_current_task())
>  	info->exectime = xnarch_tsc_to_ns(
>  		xnthread_get_exectime(&task->thread_base) +
>  		xnstat_runtime_now() -
>  		xnthread_get_lastswitch(&task->thread_base));
> +	else 
> +	  info->exectime = xnarch_tsc_to_ns(xnthread_get_exectime(&task->thread_base));

OK, second bug taken. But you approach was written without SMP in mind
(while I thought too much about SMP). The correct condition is "task is
running, somewhere?":

if (task->thread_base.sched->runthread == &task->thread_base)
	<exectime up to now>
else
	<currently stored exectime>

Of course, one may still optimise the expression.

>  	info->modeswitches = xnstat_counter_get(&task->thread_base.stat.ssw);
>  	info->ctxswitches = xnstat_counter_get(&task->thread_base.stat.csw);
>  	info->pagefaults = xnstat_counter_get(&task->thread_base.stat.pf);
> 
> 

Jan


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