Re: [PATCH v4 2/2] sched/topology: Improve load balancing on AMD EPYC

[Guenter Roeck]

On 10/9/19 5:04 AM, Matt Fleming wrote:
> On Mon, 07 Oct, at 08:28:16AM, Guenter Roeck wrote:
> > This patch causes build errors on systems where NUMA does not depend on SMP,
> > for example MIPS and PPC. For example, building mips:ip27_defconfig with SMP
> > disabled results in
> >
> > mips-linux-ld: mm/page_alloc.o: in function `get_page_from_freelist':
> > page_alloc.c:(.text+0x5018): undefined reference to `node_reclaim_distance'
> > mips-linux-ld: page_alloc.c:(.text+0x5020): undefined reference to `node_reclaim_distance'
> > mips-linux-ld: page_alloc.c:(.text+0x5028): undefined reference to `node_reclaim_distance'
> > mips-linux-ld: page_alloc.c:(.text+0x5040): undefined reference to `node_reclaim_distance'
> > Makefile:1074: recipe for target 'vmlinux' failed
> > make: *** [vmlinux] Error 1
> >
> > I have seen a similar problem with one of my PPC test builds.
> >
> > powerpc64-linux-ld: mm/page_alloc.o:(.toc+0x18): undefined reference to `node_reclaim_distance'
>
> Thanks for this Guenter.
>
> So, the way I've fixed this same issue for ia64 was to make NUMA
> depend on SMP. Does that seem like a suitable solution for both PPC
> and MIPS?

You would still have to cover all other architectures where SMP and NUMA are independent
of each other. Fortunately, it looks like this is only sh4.

sh4-linux-ld: mm/page_alloc.o: in function `get_page_from_freelist':
page_alloc.c:(.text+0x3ce0): undefined reference to `node_reclaim_distance'
Makefile:1074: recipe for target 'vmlinux' failed
make: *** [vmlinux] Error 1

arm64 and s390 happen to work because they mandate SMP support, even though NUMA
is nominally independent.

Wondering - why not declare node_reclaim_distance outside SMP dependency ?

Thanks,
Guenter