Re: [PATCH v3] mm: make expand_downwards symmetrical to expand_upwards

[KOSAKI Motohiro]

> On Wed, Apr 20, 2011 at 4:23 AM, KOSAKI Motohiro
> <kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
> > I'm worry about this patch. A lot of mm code assume !NUMA systems
> > only have node 0. Not only SLUB.
> 
> So is that a valid assumption or not? Christoph seems to think it is
> and James seems to think it's not. Which way should we aim to fix it?
> Would be nice if other people chimed in as we already know what James
> and Christoph think.

I'm sorry. I don't know it really. The fact was gone into historical myst. ;-)

Now, CONFIG_NUMA has mainly five meanings.

1) system may has !0 node id.
2) compile mm/mempolicy.c (ie enable mempolicy APIs)
3) Allocator (kmalloc, vmalloc, alloc_page, et al) awake NUMA topology.
4) enable zone-reclaim feature
5) scheduler makes per-node load balancing scheduler domain

Anyway, we have to fix this issue.  I'm digging which fixing way has least risk.


btw, x86 don't have an issue. Probably it's a reason why this issue was neglected
long time.

arch/x86/Kconfig
-------------------------------------
config ARCH_DISCONTIGMEM_ENABLE
        def_bool y
        depends on NUMA && X86_32



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