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

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Date:   Tue, 27 Sep 2022 09:01:23 +0000
From:   "tan.shaopeng@...itsu.com" <tan.shaopeng@...itsu.com>
To:     'Reinette Chatre' <reinette.chatre@...el.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 Reinette,

> (typo in Subject: initalization -> initialization)

Thanks.

> 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)".

> >
> > Clear unused initialization code in MBM test, such as CMT test.
> 
> Could the initialization code be fixed instead to increment the number of runs
> later, similar to cat_setup()?

In cat test(cat_test.c), resctrl_val_param.mum_resctrlfs is set to 0,
and cat test need to reset schemata by write_schemata().
MBM and CMT are monitoring test, and their resctrl_val_param.mum_resctrlfs is set to 1,
I think it is better to make mbm_setup() similar to cmt_setup() .

> >
> > Signed-off-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> > ---
> >  tools/testing/selftests/resctrl/mbm_test.c | 17 ++++++-----------
> >  1 file changed, 6 insertions(+), 11 deletions(-)
> >
> > diff --git a/tools/testing/selftests/resctrl/mbm_test.c
> > b/tools/testing/selftests/resctrl/mbm_test.c
> > index 8392e5c55ed0..38a3b3ad1c76 100644
> > --- a/tools/testing/selftests/resctrl/mbm_test.c
> > +++ b/tools/testing/selftests/resctrl/mbm_test.c
> > @@ -89,24 +89,19 @@ static int check_results(int span)  static int
> > mbm_setup(int num, ...)  {
> >  	struct resctrl_val_param *p;
> > -	static int num_of_runs;
> >  	va_list param;
> > -	int ret = 0;
> > -
> > -	/* Run NUM_OF_RUNS times */
> > -	if (num_of_runs++ >= NUM_OF_RUNS)
> > -		return -1;
> >
> >  	va_start(param, num);
> >  	p = va_arg(param, struct resctrl_val_param *);
> >  	va_end(param);
> >
> > -	/* Set up shemata with 100% allocation on the first run. */
> > -	if (num_of_runs == 0)
> > -		ret = write_schemata(p->ctrlgrp, "100", p->cpu_no,
> > -				     p->resctrl_val);
> > +	/* Run NUM_OF_RUNS times */
> > +	if (p->num_of_runs >= NUM_OF_RUNS)
> > +		return -1;
> 
> You seem to be fixing two bugs in this patch, the first is described in the
> commit message and the second is to use p->num_of_runs instead of the
> local num_of_runs. Although, after a quick look I cannot see if struct
> resctrl_val_param->num_of_runs is used anywhere. Could you please add
> description of these changes to the changelog?

Your observation is right.
I will add description of num_of_runs to the changelog in the next version.

Best Regards,
Shaopeng

> > +
> > +	p->num_of_runs++;
> >
> > -	return ret;
> > +	return 0;
> >  }
> >
> >  void mbm_test_cleanup(void)
> 
> Thank you
> 
> Reinette