Re: [PATCH v2 00/13] arch, mm: deprecate DISCONTIGMEM

Mike Rapoport
2020-11-17T06:23:16Z

Hi Adrian,

On Tue, Nov 17, 2020 at 06:24:51AM +0100, John Paul Adrian Glaubitz wrote:
> Hi!
>
> On 11/1/20 6:04 PM, Mike Rapoport wrote:
> > It's been a while since DISCONTIGMEM is generally considered deprecated,
> > but it is still used by four architectures. This set replaces DISCONTIGMEM
> > with a different way to handle holes in the memory map and marks
> > DISCONTIGMEM configuration as BROKEN in Kconfigs of these architectures with
> > the intention to completely remove it in several releases.
> >
> > While for 64-bit alpha and ia64 the switch to SPARSEMEM is quite obvious
> > and was a matter of moving some bits around, for smaller 32-bit arc and
> > m68k SPARSEMEM is not necessarily the best thing to do.
> >
> > On 32-bit machines SPARSEMEM would require large sections to make section
> > index fit in the page flags, but larger sections mean that more memory is
> > wasted for unused memory map.
> >
> > Besides, pfn_to_page() and page_to_pfn() become less efficient, at least on
> > arc.
> >
> > So I've decided to generalize arm's approach for freeing of unused parts of
> > the memory map with FLATMEM and enable it for both arc and m68k. The
> > details are in the description of patches 10 (arc) and 13 (m68k).
>
> Apologies for the late reply. Is this still relevant for testing?
>
> I have already successfully tested v1 of the patch set, shall I test v2?

There were minor differences only for m68k between the versions. I've
verified them on ARAnyM but if you have a real machine a run there would
be nice.

> Adrian
>
> --
> .''`. John Paul Adrian Glaubitz
> : :' : Debian Developer - glaubitz@debian.org
> `. `' Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
> `- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
>
>

--
Sincerely yours,
Mike.