linux-kernel - Re: [PATCH v4 10/19] selftests/resctrl: Express span internally in bytes

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Message-ID: <0c94daef-3642-9e8e-0e8a-3f8eaa2953e3@intel.com>
Date:   Fri, 14 Jul 2023 08:43:58 +0200
From:   "Wieczor-Retman, Maciej" <maciej.wieczor-retman@...el.com>
To:     Reinette Chatre <reinette.chatre@...el.com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        <linux-kselftest@...r.kernel.org>, Shuah Khan <shuah@...nel.org>,
        "Shaopeng Tan" <tan.shaopeng@...fujitsu.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 10/19] selftests/resctrl: Express span internally in
 bytes

Hi Reinette!

On 14.07.2023 01:00, Reinette Chatre wrote:
> Hi Ilpo,
> 
> On 7/13/2023 6:19 AM, Ilpo Järvinen wrote:
>> MBA and MBM tests to use megabytes to represent span. CMT test uses
>> bytes. The difference requires run_benchmark() to size the buffer
>> differently based on the test name, which in turn requires passing the
>> test name into run_benchmark().
>>
>> Convert MBA and MBM tests to use internally bytes like CMT test to
>> remove the internal inconsistency between the tests. Remove the test
>> dependent buffer sizing from run_benchmark().
> 
> If I understand correctly the intention is to always use bytes internally
> and only convert to megabytes when displayed to user space. The above
> implies that this takes care of the conversion but there still seems
> to be places that that do not follow my understanding. For example,
> resctrl_val.c:measure_vals() converts to megabytes before proceeding.

Doesn't the use case inside resctrl_val.c:measure_vals() satisfy
the idea of only displaying data to the user space? From my
understanding it reads the number of bytes and only converts to
MB when printing the value. Or did I miss some detail there?

> 
> While MBA, MBM, and CMT tests use resctrl_val() for testing it seems
> as though the function still exits with the MBA/MBM data recorded in
> megabytes with the CMT data recorded in bytes. That seems to be why
> show_mba_info() needs no conversion when displaying the data.
> 
> Reinette

Kind regards
Maciej Wieczór-Retman

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