Re: [RFC] mm: show message when updating min_free_kbytes in thp

Michal Hocko
2014-01-10T08:17:47Z

On Fri 10-01-14 00:13:44, Andrew Morton wrote:
> On Fri, 10 Jan 2014 09:05:04 +0100 Michal Hocko <mhocko@suse.cz> wrote:
>
> > > > --- a/mm/huge_memory.c
> > > > +++ b/mm/huge_memory.c
> > > > @@ -100,6 +100,7 @@ static struct khugepaged_scan khugepaged_scan = {
> > > > .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
> > > > };
> > > >
> > > > +extern int user_min_free_kbytes;
> > > >
> > >
> > > We don't add extern declarations to .c files. How many other examples of
> > > this can you find in mm/?
> >
> > I have suggested this because general visibility is not needed.
>
> It's best to use a common declaration which is seen by the definition
> site and all references, so everyone agrees on the variable's type.
> Otherwise we could have "long foo;" in one file and "extern char foo;"
> in another and the compiler won't tell us. I think the linker could
> tell us, but it doesn't, afaik. Perhaps there's an option...
>
> > But if
> > you think that it should then include/linux/mm.h sounds like a proper
> > place.
>
> mm/internal.h might suit.

min_free_kbytes is in mm.h so I thought having them together would be
appropriate.

--
Michal Hocko
SUSE Labs