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From:   Long Li <longli@microsoft.com>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC:     "longli@linuxonhyperv.com" <longli@linuxonhyperv.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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        Stephen Hemminger <sthemmin@microsoft.com>,
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        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Hans de Goede <hdegoede@redhat.com>,
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Subject: RE: [Patch v2 2/3] Drivers: hv: add Azure Blob driver
Thread-Topic: [Patch v2 2/3] Drivers: hv: add Azure Blob driver
Thread-Index: AQHXalTR5lVKFlOZkEmq8/y9Kgt/basqijaAgAMsL9CAAC4xgIAAgSdQ
Date:   Thu, 1 Jul 2021 17:24:29 +0000
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> Subject: Re: [Patch v2 2/3] Drivers: hv: add Azure Blob driver
>=20
> On Thu, Jul 01, 2021 at 06:58:35AM +0000, Long Li wrote:
> > > Subject: Re: [Patch v2 2/3] Drivers: hv: add Azure Blob driver
> > > > +
> > > > +static struct az_blob_device az_blob_dev;
> > > > +
> > > > +static int az_blob_ringbuffer_size =3D (128 * 1024);
> > > > +module_param(az_blob_ringbuffer_size, int, 0444);
> > > > +MODULE_PARM_DESC(az_blob_ringbuffer_size, "Ring buffer size
> > > > +(bytes)");
> > >
> > > This is NOT the 1990's, please do not create new module parameters.
> > > Just make this work properly for everyone.
> >
> > The default value is chosen so that it works best for most workloads wh=
ile
> not taking too much system resources. It should work out of box for nearl=
y all
> customers.
>=20
> Please wrap your email lines :(
>=20
> Anyway, great, it will work for everyone, no need for this to be changed.
> Then just drop it.
>=20
> > But what we see is that from time to time, some customers still want to
> change those values to work best for their workloads. It's hard to predic=
t their
> workload. They have to recompile the kernel if there is no module paramet=
er
> to do it. So the intent of this module parameter is that if the default v=
alue
> works for you, don't mess up with it.
>=20
> Can you not just determine at runtime that these workloads are overflowin=
g
> the buffer and increase the size of it?  That would be best otherwise you=
 are
> forced to try to deal with a module parameter that is for code, not for d=
evices
> (which is why we do not like module parameters for drivers.)
>=20
> Please remove this for now and if you _REALLY_ need it in the future, mak=
e it
> auto-tunable.  Or if that is somehow impossible, then make it a per-devic=
e
> option, through something like sysfs so that it will work correctly per-d=
evice.
>=20
> thanks,
>=20
> greg k-h

I got your point, will be removing this.=20

Thanks,
Long