linux-kernel - Re: [PATCH V3 15/15] selftests/resctrl: Replace magic constants used as array size

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Message-ID: <805a7c70-9a0b-a50a-3985-895f9d2c5fd4@linux.intel.com>
Date: Fri, 18 Oct 2024 12:08:45 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Reinette Chatre <reinette.chatre@...el.com>
cc: fenghua.yu@...el.com, shuah@...nel.org, tony.luck@...el.com, 
    peternewman@...gle.com, babu.moger@....com, 
    Maciej Wieczór-Retman <maciej.wieczor-retman@...el.com>, 
    linux-kselftest@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 15/15] selftests/resctrl: Replace magic constants used
 as array size

On Thu, 17 Oct 2024, Reinette Chatre wrote:

> The Memory Bandwidth Allocation (MBA) test iterates through all possible
> MBA allocations, from 10% (ALLOCATION_MIN) to 100% (ALLOCATION_MAX) with
> increments of 10% (ALLOCATION_STEP) at each iteration. During each
> iteration the test measures the actual memory bandwidth NUM_OF_RUNS times
> to determine the impact of MBA on actual memory bandwidth.
> 
> After the MBA test completes all the memory bandwidth measurements are
> parsed into an array. One array for resctrl Memory Bandwidth Monitoring
> (MBM) measurements and one array for the Integrated Memory Controller
> (iMC) measurements. Each array has a hardcoded size of 1024 that is
> large enough to hold the current test data, but this hardcoded value makes
> the implementation difficult to understand. It will not be clear that this
> array needs to be reconsidered if any of the test parameters are changed.
> 
> Replace the magic constant as array size with the test parameters the
> array size depends on.
> 
> Reported-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Closes: https://lore.kernel.org/all/45af2a8c-517d-8f0d-137d-ad0f3f6a3c68@linux.intel.com/
> Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

--
 i.

> ---
> Changes since V2:
> - New patch.
> ---
>  tools/testing/selftests/resctrl/mba_test.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c
> index 4e6645b172e3..536d9089d2f6 100644
> --- a/tools/testing/selftests/resctrl/mba_test.c
> +++ b/tools/testing/selftests/resctrl/mba_test.c
> @@ -127,8 +127,9 @@ static bool show_mba_info(unsigned long *bw_imc, unsigned long *bw_resc)
>  
>  static int check_results(void)
>  {
> +	unsigned long bw_resc[NUM_OF_RUNS * ALLOCATION_MAX / ALLOCATION_STEP];
> +	unsigned long bw_imc[NUM_OF_RUNS * ALLOCATION_MAX / ALLOCATION_STEP];
>  	char *token_array[8], output[] = RESULT_FILE_NAME, temp[512];
> -	unsigned long bw_imc[1024], bw_resc[1024];
>  	int runs;
>  	FILE *fp;
>  
>