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

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Date:   Wed, 28 Sep 2022 08:48:09 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     "tan.shaopeng@...itsu.com" <tan.shaopeng@...itsu.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Shuah Khan <shuah@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH 1/5] selftests/resctrl: Clear unused initalization code in
 MBM tests

Hi Shaopeng,

On 9/27/2022 2:01 AM, tan.shaopeng@...itsu.com wrote:
>> 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.
> 
> In mbm test(mbm_test.c), resctrl_val_param.mum_resctrlfs is set to 1 and never be changed,
> and umount/mount resctrl file system is always executed.
> So it is not necessary to run "if (num_of_runs == 0)".

This is true for the current usage. You could also add a warning here
("running test with stale config") if a future test sets mum_resctrlfs - but
with all the current output of the selftests a warning may be lost in the noise.

I think it would just be simpler to support both cases. Having the tests be more
robust is good.

Reinette