Re: [dpdk-dev] [PATCH v5 1/2] test/power: add delay before checking cpuinfo cur freq

[David Hunt <david.hunt@intel.com>]

On 15/4/2021 6:59 AM, Richael Zhuang wrote:
> For some platforms the newly-set frequency may not be effective
> immediately. If we didn't get the right value from cpuinfo_cur_freq
> immediately, add 10ms delay each time before rechecking until
> timeout.
>
>  From our test, for some arm platforms, it requires up to 700ms when
> going from a minimum to a maximum frequency. And it's not the
> driver/software issue.
>
> Fixes: ed7c51a6a680 ("app/test: vm power management")
> Cc: alan.carew@intel.com
> Cc: stable@dpdk.org
>
> Signed-off-by: Richael Zhuang <richael.zhuang@arm.com>
> ---
>   app/test/test_power_cpufreq.c | 27 ++++++++++++++++++++++-----
>   1 file changed, 22 insertions(+), 5 deletions(-)
>
> diff --git a/app/test/test_power_cpufreq.c b/app/test/test_power_cpufreq.c
> index 731c6b4dc..d47b3e0a1 100644
> --- a/app/test/test_power_cpufreq.c
> +++ b/app/test/test_power_cpufreq.c
> @@ -8,6 +8,7 @@
>   #include <limits.h>
>   #include <string.h>
>   #include <inttypes.h>
> +#include <rte_cycles.h>
>   
>   #include "test.h"
>   
> @@ -44,11 +45,13 @@ static int
>   check_cur_freq(unsigned lcore_id, uint32_t idx)
>   {
>   #define TEST_POWER_CONVERT_TO_DECIMAL 10
> +#define MAX_LOOP 100
>   	FILE *f;
>   	char fullpath[PATH_MAX];
>   	char buf[BUFSIZ];
>   	uint32_t cur_freq;
>   	int ret = -1;
> +	int i;
>   
>   	if (snprintf(fullpath, sizeof(fullpath),
>   		TEST_POWER_SYSFILE_CUR_FREQ, lcore_id) < 0) {
> @@ -58,13 +61,27 @@ check_cur_freq(unsigned lcore_id, uint32_t idx)
>   	if (f == NULL) {
>   		return 0;
>   	}
> -	if (fgets(buf, sizeof(buf), f) == NULL) {
> -		goto fail_get_cur_freq;
> +	for (i = 0; i < MAX_LOOP; i++) {
> +		fflush(f);
> +		if (fgets(buf, sizeof(buf), f) == NULL)
> +			goto fail_all;
> +
> +		cur_freq = strtoul(buf, NULL, TEST_POWER_CONVERT_TO_DECIMAL);
> +		ret = (freqs[idx] == cur_freq ? 0 : -1);
> +
> +		if (ret == 0)
> +			break;
> +
> +		if (fseek(f, 0, SEEK_SET) < 0) {
> +			printf("Fail to set file position indicator to 0\n");
> +			goto fail_all;
> +		}
> +
> +		/* wait for the value to be updated */
> +		rte_delay_ms(10);
>   	}
> -	cur_freq = strtoul(buf, NULL, TEST_POWER_CONVERT_TO_DECIMAL);
> -	ret = (freqs[idx] == cur_freq ? 0 : -1);
>   
> -fail_get_cur_freq:
> +fail_all:
>   	fclose(f);
>   
>   	return ret;

Hi Richael

On your system, is the current cpu frequency found in cpuinfo_cur_freq 
or in scaling_cur_freq? On my system, which uses intel_pstate driver, 
there is no file called cpuinfo_cur_freq, but the test works when I 
change TEST_POWER_SYSFILE_CUR_FREQ to scaling_cur_freq.

I know that's unrelated to your patch above, but it migth be worth using 
a file common to all platforms, or else attempting to open one, and if 
that fails, try open the other.

Rgds,
Dave.