linux-kernel - Re: [PATCH v2 17/24] selftests/resctrl: Replace count_bits with count_consecutive

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Message-ID: <7bb3f116-2f4d-b81a-3f49-dae7175e82c1@linux.intel.com>
Date:   Tue, 25 Apr 2023 14:41:48 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Reinette Chatre <reinette.chatre@...el.com>
cc:     linux-kselftest@...r.kernel.org, Fenghua Yu <fenghua.yu@...el.com>,
        Shuah Khan <shuah@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Subject: Re: [PATCH v2 17/24] selftests/resctrl: Replace count_bits with
 count_consecutive_bits()

On Fri, 21 Apr 2023, Reinette Chatre wrote:
> On 4/18/2023 4:44 AM, Ilpo Järvinen wrote:
> > CAT and CMT tests depends on masks being continuous.
> 
> The term used in the spec is "contiguous", using it here
> may help to convey the goal.
> 
> > 
> > Replace count_bits with more appropriate variant that counts
> > consecutive bits.
> 
> Could you please elaborate why this is more appropriate and
> why this is necessary? What is wrong with current solution?
> 
> Please note that cbm_mask in resctrl will always be contiguous.

Hi,

It's good that you asked this question.

This comes from a change (not by me originally) that also excluded the 
shareable bits from the mask the CAT test uses. I assumed (w/o better 
knowledge) that those shareable bits could create a hole into the mask.

It could be wrong assumption and the shareable bits are always at one end 
of the CBM mask.

Do you happen to know how the shareable bits are positioned within the 
mask?


-- 
 i.