Re: [PATCH v2 0/7] mm/hotplug: Only use subsection map in VMEMMAP case

Michal Hocko
2020-02-25T10:02:31Z

On Tue 25-02-20 10:10:45, David Hildenbrand wrote:
> >>> include/linux/mmzone.h | 2 +
> >>> mm/sparse.c | 178 +++++++++++++++++++++++++++++------------
> >>> 2 files changed, 127 insertions(+), 53 deletions(-)
> >>
> >> Why do we need to add so much code to remove a functionality from one
> >> memory model?
> >
> > Hmm, Dan also asked this before.
> >
> > The adding mainly happens in patch 2, 3, 4, including the two newly
> > added function defitions, the code comments above them, and those added
> > dummy functions for !VMEMMAP.
>
> AFAIKS, it's mostly a bunch of newly added comments on top of functions.
> E.g., the comment for fill_subsection_map() alone spans 12 LOC in total.
> I do wonder if we have to be that verbose. We are barely that verbose on
> MM code (and usually I don't see much benefit unless it's a function
> with many users from many different places).

I would tend to agree here. Not that I am against kernel doc
documentation but these are internal functions and the comment doesn't
really give any better insight IMHO. I would be much more inclined if
this was the general pattern in the respective file but it just stands
out.
--
Michal Hocko
SUSE Labs