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

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Date:   Thu, 13 Jul 2023 16:00:38 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     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 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.

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