Rough notes from Kernel Consolidation meeting

[Nicolas Pitre]

On Mon, 20 Sep 2010, Paul E. McKenney wrote:

> On Mon, Sep 20, 2010 at 06:37:05PM +0200, Arnd Bergmann wrote:
> > On Monday 20 September 2010, Paul E. McKenney wrote:
> > > o       Kernel requirements
> > >         (https://wiki.linaro.org/Internal/TSC/MinutesToBeAgreed)
> > > 
> > 
> > I still have two questions about stuff that came up here:
> > 
> > * SD/MMC performance: Is this about device access, file systems or both?
> >   I think the file system level stuff is actually the more important
> >   part but I fear that what was discussed is the other one.
> 
> The discussion didn't get into that level of detail.  :-(
> 
> > * highmem: Not sure what this was about. I guess we don't really want
> >   to enable this by default, but some people will want it anyway.
> >   Is this about run-time patching the code out of the kernel?
> 
> I believe that this is related to LPAE -- the usual 32-bit-only DMA
> devices in a >32-bit physical address space.  But there was also
> discussion about run-time patching for SMP alternatives, though I am
> missing how this relates to highmem.  Enlightenment?

I'm also interested in both of those topics as 1) I participated in the 
design of the SDIO stack (closely related to SD), and 2) I did the 
highmem implementation for ARM.

Wrt SD/MMC performance, if we're talking about device access, then all 
the DMA-using hardware configs I've seen are only limited by the media 
speed which is typically much slower than a hard disk, or even a SSD for 
that matter (and so is the price).

Wrt highmem: I can't see the link with highmem and SMP.  As far as I 
know, highmem on ARM should be SMP safe already (the only SMP related 
issue I've seen has been fixed in commit 831e8047eb).


Nicolas