Re: [PATCH 3/7] Allow CONFIG_MIGRATION to be set without CONFIG_NUMA

[Mel Gorman <mel@csn.ul.ie>]

On Tue, 29 May 2007, Christoph Lameter wrote:

> On Tue, 29 May 2007, Mel Gorman wrote:
>
> > > > +config SYSCALL_MOVE_PAGES
> > > > +	def_bool y
> > > > +	depends on MIGRATION && NUMA
> > > > +
> > >
> > > Do we really need the CONFIG_SYSCALL_MOVE_PAGES? I think you will directly
> > > access the lower levels. So why have it? CONFIG_SYSCALL_MOVE_PAGES ==
> > > CONFIG_NUMA.
> >
> > Without SYSCALL_MOVE_PAGES, the check in migrate.h becomes
> >
> > #if defined(CONFIG_NUMA) && defined(CONFIG_MIGRATION)
> > /* Check if a vma is migratable */
> > static inline int vma_migratable(struct vm_area_struct *vma)
> > #endif
>
> Why do you need vma_migratable for the CONFIG_MIGRATION case? The use of
> vma_migratable in a !NUMA sitation would not be working right as far as I
> can tell.
>
> #ifdef CONFIG_NUMA
>
> is fine.

Makes sense.

> > That in itself is fine but in mm/migrate.c I didn't want to define
> > sys_move_pages() in the non-NUMA case. Whatever about the header file where
> > SYSCALL_MOVE_PAGES obscures understanding, I think it makes sense to have
> > SYSCALL_MOVE_PAGES for mm/migrate.c . What do you think?
>
> Why do you need sys_move_pages for the non-NUMA case?
>
> The low level function that I intended to be used by defrag is
> migrate_pages and that one is outside of #ifdef CONFIG_NUMA.

Also make sense. It'll be fixed up in the next verion minus the 
SYSCALL_MOVE_PAGES dirt. It'll even simplify the patch.

--
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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