Re: intel_turbo_max_3 non-modularity

[Darren Hart <dvhart@infradead.org>]

On Fri, Apr 28, 2017 at 11:34:34PM +0200, Peter Zijlstra wrote:
> On Fri, Apr 28, 2017 at 01:49:49PM -0700, Darren Hart wrote:
> > > > Non-modular drivers do not scale. This is a serious issue considering
> > > > the growth rate of the kernel.
> > > 
> > > Again, this is an oversimplification that doesn't reflect reality.
> > > There are many valid reasons why some drivers be built-in only.  The
> > > whole world isn't a distro looking to say "=m" to every config option
> > > simply because they don't have the time or resources to actually triage
> > > them all and see what is relevant for their use case(es).
> > > 
> > 
> > The point is valid though, and something we need to be keeping an eye on,
> > especially with all the non-architectural SoC feature drivers we're seeing code
> > roll in for. I appreciate you raising the concern Jean.
> 
> FWIW:
> 
> There's things like ACPI-Processor-Idle and intel_idle that need to be
> built-in for correctness sake.
> 
> They can mark the TSC unstable, and this should be done before we run
> userspace, which with unstable TSC could see wobbly time before we kill
> the TSC.
> 
> This is a somewhat non-obvious case, and on the face of it those could
> be modular drivers. But building them as modules gets them loaded far
> too late if ever.
> 
> These are subtle things and easily overlooked.

Thanks Peter, I will be sure to do my due diligence in determining why something
may be bool before applying incoming patches to change that. This isn't clearly
documented in intel_idle for example, but it is at least explicitly described in
the git log for the Kconfig.

-- 
Darren Hart
VMware Open Source Technology Center