linux-kernel - Re: [PATCH 3/8] scsi: ufshpb: Add region's reads counter

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Date:   Mon, 1 Feb 2021 09:01:07 +0100
From:   "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To:     Avri Altman <Avri.Altman@....com>
Cc:     "daejun7.park@...sung.com" <daejun7.park@...sung.com>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Bart Van Assche <bvanassche@....org>,
        yongmyung lee <ymhungry.lee@...sung.com>,
        ALIM AKHTAR <alim.akhtar@...sung.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        Zang Leigang <zangleigang@...ilicon.com>,
        Avi Shchislowski <Avi.Shchislowski@....com>,
        Bean Huo <beanhuo@...ron.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>
Subject: Re: [PATCH 3/8] scsi: ufshpb: Add region's reads counter

On Mon, Feb 01, 2021 at 07:51:19AM +0000, Avri Altman wrote:
> > 
> > On Mon, Feb 01, 2021 at 07:12:53AM +0000, Avri Altman wrote:
> > > > > +#define WORK_PENDING 0
> > > > > +#define ACTIVATION_THRSHLD 4 /* 4 IOs */
> > > > Rather than fixing it with macro, how about using sysfs and make it
> > > > configurable?
> > > Yes.
> > > I will add a patch making all the logic configurable.
> > > As all those are hpb-related parameters, I think module parameters are
> > more adequate.
> > 
> > No, this is not the 1990's, please never add new module parameters to
> > drivers.  If not for the basic problem of they do not work on a
> > per-device basis, but on a per-driver basis, which is what you almost
> > never want.
> OK.
> 
> > 
> > But why would you want to change this value, why can't the driver "just
> > work" and not need manual intervention?
> It is.
> But those are a knobs each vendor may want to tweak,
> So it'll be optimized with its internal device's implementation.
> 
> Tweaking the parameters, as well as the entire logic, is really an endless task.
> Some logic works better for some scenarios, while falling behind on others.

Shouldn't the hardware know how to handle this dynamically?  If not, how
is a user going to know?

> How about leaving it for now, to be elaborated it in the future?

I do not care, just do not make it a module parameter for the reason
that does not work on a per-device basis.

> Maybe even can be a part of a scheme, to make the logic proprietary?

What do you mean by "proprietary"?

thanks,

greg k-h