Re: [RFC/RFT PATCH 1/3] memblock: update initialization of reserved pages

[David Hildenbrand]

On 16.04.21 13:44, Mike Rapoport wrote:
> On Thu, Apr 15, 2021 at 11:30:12AM +0200, David Hildenbrand wrote:
> > > Not sure we really need a new pagetype here, PG_Reserved seems to be quite
> > > enough to say "don't touch this".  I generally agree that we could make
> > > PG_Reserved a PageType and then have several sub-types for reserved memory.
> > > This definitely will add clarity but I'm not sure that this justifies
> > > amount of churn and effort required to audit uses of PageResrved().
> > > > Then, we could mostly avoid having to query memblock at runtime to figure
> > > > out that this is special memory. This would obviously be an extension to
> > > > this series. Just a thought.
> > >
> > > Stop pushing memblock out of kernel! ;-)
> >
> > Can't stop. Won't stop. :D
> >
> > It's lovely for booting up a kernel until we have other data-structures in
> > place ;)
>
> A bit more seriously, we don't have any data structure that reliably
> represents physical memory layout and arch-independent fashion.
> memblock is probably the best starting point for eventually having one.

We have the (slowish) kernel resource tree after boot and the (faster) 
memmap. I really don't see why we really need another slowish variant.

We might be better off to just extend and speed up the kernel resource tree.

Memblock as is is not a reasonable datastructure to keep around after 
boot: for example, how we handle boottime allocations and reserve 
regions both as reserved.

--
Thanks,

David / dhildenb