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Date: Thu, 13 Feb 2014 14:45:49 -0800 (PST)
From: David Rientjes <rientjes@google.com>
To: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Subject: Re: [PATCH] powerpc: enable CONFIG_HAVE_MEMORYLESS_NODES
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 <20140213214131.GB12409@linux.vnet.ibm.com>
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Cc: Pekka Enberg <penberg@kernel.org>, linux-mm@kvack.org,
 Paul Mackerras <paulus@samba.org>, Anton Blanchard <anton@samba.org>,
 Matt Mackall <mpm@selenic.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
 linuxppc-dev@lists.ozlabs.org, Christoph Lameter <cl@linux.com>,
 Wanpeng Li <liwanp@linux.vnet.ibm.com>
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On Thu, 13 Feb 2014, Nishanth Aravamudan wrote:

> > Anton Blanchard found an issue with an LPAR that had no memory in Node
> > 0. Christoph Lameter recommended, as one possible solution, to use
> > numa_mem_id() for locality of the nearest memory node-wise. However,
> > numa_mem_id() [and the other related APIs] are only useful if
> > CONFIG_HAVE_MEMORYLESS_NODES is set. This is only the case for ia64
> > currently, but clearly we can have memoryless nodes on ppc64. Add the
> > Kconfig option and define it to be the same value as CONFIG_NUMA.
> > 
> > On the LPAR in question, which was very inefficiently using slabs, this
> > took the slab consumption at boot from roughly 7GB to roughly 4GB.
> 
> Err, this should have been
> 
> Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
> 
> !
> 
> Sorry about that Ben!
>     
> > ---
> > Ben, the only question I have wrt this change is if it's appropriate to
> > change it for all powerpc configs (that have NUMA on)?
> > 

I'm suspecting that Ben will request that the proper set_numa_mem() calls 
are done for ppc init to make this actually do anything other than return 
numa_mem_id() == numa_node_id().

> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > index 25493a0..bb2d5fe 100644
> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -447,6 +447,9 @@ config NODES_SHIFT
> >  	default "4"
> >  	depends on NEED_MULTIPLE_NODES
> >  
> > +config HAVE_MEMORYLESS_NODES
> > +	def_bool NUMA
> > +
> >  config ARCH_SELECT_MEMORY_MODEL
> >  	def_bool y
> >  	depends on PPC64