linux-kernel - Re: [PATCH v2 6/6] selftests/resctrl: Reduce failures due to outliers in MBA/MBM tests

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Message-ID: <37888890-bfba-c3d9-558f-4c6e830669f0@intel.com>
Date:   Tue, 26 Sep 2023 14:41:59 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Shuah Khan <shuah@...nel.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        <linux-kselftest@...r.kernel.org>,
        Maciej Wieczór-Retman 
        <maciej.wieczor-retman@...el.com>
CC:     LKML <linux-kernel@...r.kernel.org>,
        Shaopeng Tan <tan.shaopeng@...fujitsu.com>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH v2 6/6] selftests/resctrl: Reduce failures due to outliers
 in MBA/MBM tests

Hi Ilpo,

On 9/15/2023 8:44 AM, Ilpo Järvinen wrote:
> The initial value of 5% chosen for the maximum allowed percentage
> difference between resctrl mbm value and IMC mbm value in commit
> 06bd03a57f8c ("selftests/resctrl: Fix MBA/MBM results reporting
> format") was "randomly chosen value" (as admitted by the changelog).
> 
> When running tests in our lab across a large number platforms, 5%
> difference upper bound for success seems a bit on the low side for the
> MBA and MBM tests. Some platforms produce outliers that are slightly
> above that, typically 6-7%, which leads MBA/MBM test frequently
> failing.
> 
> Replace the "randomly chosen value" with a success bound that is based
> on those measurements across large number of platforms by relaxing the
> MBA/MBM success bound to 8%. The relaxed bound removes the failures due
> the frequent outliers.
> 
> Fixes: 06bd03a57f8c ("selftests/resctrl: Fix MBA/MBM results reporting format")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

Thank you.

Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>

Reinette