Hi Randy, On Wed, Apr 24, 2019 at 06:08:46PM -0700, Randy Dunlap wrote: > On 4/24/19 3:28 AM, Mike Rapoport wrote: > > Describe what {FLAT,DISCONTIG,SPARSE}MEM are and how they manage to > > maintain pfn <-> struct page correspondence. > > > > Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> > > --- > > Documentation/vm/index.rst | 1 + > > Documentation/vm/memory-model.rst | 171 ++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 172 insertions(+) > > create mode 100644 Documentation/vm/memory-model.rst > > > > Hi Mike, > I have a few minor edits below... I kinda expected those ;-) > > diff --git a/Documentation/vm/memory-model.rst b/Documentation/vm/memory-model.rst > > new file mode 100644 > > index 0000000..914c52a > > --- /dev/null > > +++ b/Documentation/vm/memory-model.rst ... > > + > > +With FLATMEM, the conversion between a PFN and the `struct page` is > > +straightforward: `PFN - ARCH_PFN_OFFSET` is an index to the > > +`mem_map` array. > > + > > +The `ARCH_PFN_OFFSET` defines the first page frame number for > > +systems that their physical memory does not start at 0. > > s/that/when/ ? Seems awkward as is. Yeah, it is awkward. How about The `ARCH_PFN_OFFSET` defines the first page frame number for systems with physical memory starting at address different from 0. > > + > > +DISCONTIGMEM > > +============ > > + > > thanks. > -- > ~Randy > -- Sincerely yours, Mike.