linux-kernel - Re: [PATCH v4 08/17] selftests/resctrl: Ensure sibling CPU is not same as original CPU

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Date:   Mon, 25 Jan 2021 19:35:08 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Fenghua Yu <fenghua.yu@...el.com>, Shuah Khan <shuah@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        David Binderman <dcb314@...mail.com>,
        Babu Moger <babu.moger@....com>,
        James Morse <james.morse@....com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Shuah Khan <skhan@...uxfoundation.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 08/17] selftests/resctrl: Ensure sibling CPU is not
 same as original CPU

On 11/30/20 1:20 PM, Fenghua Yu wrote:
> From: Reinette Chatre <reinette.chatre@...el.com>
> 
> The resctrl tests can accept a CPU on which the tests are run and use
> default of CPU #1 if it is not provided. In the CAT test a "sibling CPU"
> is determined that is from the same package where another thread will be
> run.
> 
> The current algorithm with which a "sibling CPU" is determined does not
> take the provided/default CPU into account and when that CPU is the
> first CPU in a package then the "sibling CPU" will be selected to be the
> same CPU since it starts by picking the first CPU from core_siblings_list.
> 
> Fix the "sibling CPU" selection by taking the provided/default CPU into
> account and ensuring a sibling that is a different CPU is selected.
> 
> Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> ---
>   tools/testing/selftests/resctrl/resctrlfs.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
> index d2cae4927b62..3f43bcf0b8d5 100644
> --- a/tools/testing/selftests/resctrl/resctrlfs.c
> +++ b/tools/testing/selftests/resctrl/resctrlfs.c
> @@ -268,7 +268,7 @@ int get_core_sibling(int cpu_no)
>   	while (token) {
>   		sibling_cpu_no = atoi(token);
>   		/* Skipping core 0 as we don't want to run test on core 0 */
> -		if (sibling_cpu_no != 0)
> +		if (sibling_cpu_no != 0 && sibling_cpu_no != cpu_no)
>   			break;
>   		token = strtok(NULL, "-,");
>   	}
> 

Shouldn't this be fixed first before the cleanup and restructure
changes?

Please make this patch 3.

thanks,
-- Shuah