linux-kernel - Re: [PATCH 1/5] selftests/resctrl: Clear unused initalization code in MBM tests

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Message-ID: <24cbb6e4-d853-6c7e-cffc-daa7412d1eab@intel.com>
Date:   Thu, 22 Sep 2022 10:44:05 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Shaopeng Tan <tan.shaopeng@...fujitsu.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Shuah Khan <shuah@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH 1/5] selftests/resctrl: Clear unused initalization code in
 MBM tests

Hi Shaopeng,

(typo in Subject: initalization -> initialization)

On 9/13/2022 6:51 PM, Shaopeng Tan wrote:
> There is a comment "Set up shemata with 100% allocation on the first run"
> in function mbm_setup(), but the condition "num_of_runs == 0" will
> never be met and write_schemata() will never be called to set schemata
> to 100%.

Thanks for catching this.

> 
> Since umount/mount resctrl file system is run on each resctrl test,
> at the same time the default schemata will also be set to 100%.

This is the case when a test is run with struct
resctrl_val_param->mum_resctrlfs == 1, but if the test is run with
struct
resctrl_val_param->mum_resctrlfs == 0 then resctrl filesystem will
not be remounted.

I do think that this setup function should support both cases.

> 
> Clear unused initialization code in MBM test, such as CMT test.

Could the initialization code be fixed instead to increment
the number of runs later, similar to cat_setup()?

> 
> Signed-off-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> ---
>  tools/testing/selftests/resctrl/mbm_test.c | 17 ++++++-----------
>  1 file changed, 6 insertions(+), 11 deletions(-)
> 
> diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c
> index 8392e5c55ed0..38a3b3ad1c76 100644
> --- a/tools/testing/selftests/resctrl/mbm_test.c
> +++ b/tools/testing/selftests/resctrl/mbm_test.c
> @@ -89,24 +89,19 @@ static int check_results(int span)
>  static int mbm_setup(int num, ...)
>  {
>  	struct resctrl_val_param *p;
> -	static int num_of_runs;
>  	va_list param;
> -	int ret = 0;
> -
> -	/* Run NUM_OF_RUNS times */
> -	if (num_of_runs++ >= NUM_OF_RUNS)
> -		return -1;
>  
>  	va_start(param, num);
>  	p = va_arg(param, struct resctrl_val_param *);
>  	va_end(param);
>  
> -	/* Set up shemata with 100% allocation on the first run. */
> -	if (num_of_runs == 0)
> -		ret = write_schemata(p->ctrlgrp, "100", p->cpu_no,
> -				     p->resctrl_val);
> +	/* Run NUM_OF_RUNS times */
> +	if (p->num_of_runs >= NUM_OF_RUNS)
> +		return -1;

You seem to be fixing two bugs in this patch, the first is described in the
commit message and the second is to use p->num_of_runs instead of the
local num_of_runs. Although, after a quick look I cannot see if 
struct resctrl_val_param->num_of_runs is used anywhere. Could you
please add description of these changes to the changelog?

> +
> +	p->num_of_runs++;
>  
> -	return ret;
> +	return 0;
>  }
>  
>  void mbm_test_cleanup(void)

Thank you

Reinette