Re: [Ksummit-2013-discuss] [ATTEND] [ARM ATTEND] kernel data bloatand how to avoid it

From: Greg KH
Date: Fri Aug 02 2013 - 04:10:23 EST

On Fri, Aug 02, 2013 at 12:53:53AM -0700, Tony Lindgren wrote:
> * Greg KH <greg@xxxxxxxxx> [130731 05:39]:
> > On Wed, Jul 31, 2013 at 12:38:03AM -0700, Tony Lindgren wrote:
> > > Hi all,
> > >
> > > Probably the biggest kernel data bloat issue is in the ARM land, but
> > > it also seems that it's becoming a Linux generic issue too, so I
> > > guess it could be discussed in either context.
> >
> > Why is it specific to ARM? What is so unique to ARM that causes it to
> > "bloat"?
> I think it has so far showed up on ARM because of no discoverable busses,
> but chances are it will be more of a generic problem.
> > And what exactly do you mean by "bloat"?
> Stuffing data to kernel that should not be in the kernel at all. Or
> if the data is needed by kernel, there should be only one set of the
> data defined rather than multiple copies of the data built into the
> kernel for each SoC or driver variant.
> > > Basically the data bloat issue is there for the arch code and drivers
> > > and may not show up initially until things have headed the wrong way for
> > > too long.
> >
> > What do you mean by this? You seem to be very vague here.
> People are unnecessarily defining registers in kernel for similar devices
> over and over again for each new SoC at the arch level and now more and
> more at the driver level.
> One example of that are device tree based drivers that don't describe
> the actual hardware, but instead have a binding that points to an index
> of defined registers in the driver.

Ok, and exactly how much "larger" does something like this cost as a
real number, and as a percentage of the size of the kernel?


greg k-h
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