Re: [LTP] [PATCH v3] device-drivers/ltp_acpi_cpufreq: use simple counter instead of cur_freq

[Cyril Hrubis <chrubis@suse.cz>]

Hi!
> -void *thread_fn(void *val)
> +static int load_cpu(int max_freq_khz)
>  {
> -	struct timeval tv_start;
> -	struct timeval tv_end;
> -	int i, res = 0;
> -	intptr_t timeout = (intptr_t) val;
> -
> -	gettimeofday(&tv_start, NULL);
> -	tst_resm(TINFO, "load CPU0 for %ld sec...", timeout);
> +	int sum = 0, i = 0, total_time_ms;
> +	struct timespec tv_start, tv_end;
>  
> -	do {
> -		for (i = 1; i < 10000; ++i)
> -			res += i * i;
> -		gettimeofday(&tv_end, NULL);
> -		sched_yield();
> -	} while ((tv_end.tv_sec - tv_start.tv_sec) < timeout);
> -
> -	tst_resm(TINFO, "CPU0 load done: insignificant value '%d'", res);
> +	const int max_sum = max_freq_khz / 1000;
> +	const int units = 1000000; /* Mhz */
>  
> -	return NULL;
> -}
> +	clock_gettime(CLOCK_MONOTONIC_RAW, &tv_start);
>  
> -static int load_cpu(intptr_t timeout)
> -{
> -	pthread_t thread_id;
> +	do {
> +		for (i = 0; i < units; ++i)
> +			asm ("" : : : "memory");
> +	} while (++sum < max_sum);
>  
> -	if (pthread_create(&thread_id, 0, thread_fn,
> -		(void *) timeout) != 0) {
> -		tst_brkm(TBROK | TERRNO, cleanup,
> -			"pthread_create failed at %s:%d",
> -			__FILE__, __LINE__);
> -	}
> +	clock_gettime(CLOCK_MONOTONIC_RAW, &tv_end);
>  
> -	sleep(2 * timeout / 3);
> +	total_time_ms = (tv_end.tv_sec - tv_start.tv_sec) * 1000 +
> +		(tv_end.tv_nsec - tv_start.tv_nsec) / 1000000;
>  
> -	int cur_freq;
> -	SAFE_FILE_SCANF(cleanup, curspeed, "%d", &cur_freq);
> -	tst_resm(TINFO, "got cpu freq under load: %d", cur_freq);
> +	if (!total_time_ms)
> +		tst_brkm(TBROK, cleanup, "can't calc freq, time period is 0");
>  
> -	pthread_join(thread_id, NULL);
> +	tst_resm(TINFO, "elapsed time is %d ms", total_time_ms);
>  
> -	return cur_freq;
> +	return sum * 1000 / total_time_ms;

Is this conversion really necessary? I guess that we can also return
the elapsed time here and test that the time is shorted by a few
percents with boost enabled in the test_run() function.

Otherwise it looks good.

-- 
Cyril Hrubis
chrubis@suse.cz

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