On Fri, 8 Aug 2014, Geert Uytterhoeven wrote:
> On Fri, Aug 8, 2014 at 4:44 PM, Christoph Lameter <cl@xxxxxxxxx> wrote:
> > On Fri, 8 Aug 2014, Joonsoo Kim wrote:
> >
> >> This reverts commit a640616822b2 ("slab: remove BAD_ALIEN_MAGIC").
> >
> > Lets hold off on this one. I am bit confused as to why a non NUMA system
> > would have multiple NUMA nodes.
>
> DISCONTIGMEM
>
> mm/Kconfig:
>
> #
> # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
> # to represent different areas of memory. This variable allows
> # those dependencies to exist individually.
> #
> config NEED_MULTIPLE_NODES
> def_bool y
> depends on DISCONTIGMEM || NUMA
Uhhh... And how does one access memory when the node is != 0 given that
zone_to_nid always returns 0 in the !CONFIG_NUMA case? AFAICT there are
numerous of these node == 0 assumptions in the kernel for !NUMA.
include/linux/mmzone.h:
#ifdef CONFIG_NUMA
#define pfn_to_nid(pfn) \
({ \
unsigned long __pfn_to_nid_pfn = (pfn); \
page_to_nid(pfn_to_page(__pfn_to_nid_pfn)); \
})
#else
#define pfn_to_nid(pfn) (0)
#endif
How can this work at all????
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