linux-kernel - RE: [PATCH v4] scsi: ufs: Fix imprecise load calculation in devfreq window

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Date:   Thu, 11 Jun 2020 17:52:53 +0800
From:   Stanley Chu <stanley.chu@...iatek.com>
To:     Avri Altman <Avri.Altman@....com>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
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        "cc.chou@...iatek.com" <cc.chou@...iatek.com>
Subject: RE: [PATCH v4] scsi: ufs: Fix imprecise load calculation in devfreq
 window

Hi Avri,

Thanks for the review.

On Thu, 2020-06-11 at 08:03 +0000, Avri Altman wrote:
> > 
> > Fixes: a3cd5ec55f6c ("scsi: ufs: add load based scaling of UFS gear")
> > Signed-off-by: Stanley Chu <stanley.chu@...iatek.com>
> Reviewed-by: Avri Altman <avri.altman@....com>
> 
> Just a small nit.
> 
> > -       stat->total_time = jiffies_to_usecs((long)jiffies -
> > -                               (long)scaling->window_start_t);
> > +       stat->total_time = ktime_to_us(curr_t) - scaling->window_start_t;
> ktime_sub ?

scaling->window_start_t is already in "us" thus ktime_sub() is not
suitable here.

Another way is changing scaling->window_start_t as type "ktime_t". This
is worth to do because of a little performance gain.

I will change it in next version.

Thanks,
Stanley Chu