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Date: Thu, 13 Feb 2014 13:41:31 -0800
From: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
To: Christoph Lameter <cl@linux.com>
Subject: Re: [PATCH] powerpc: enable CONFIG_HAVE_MEMORYLESS_NODES
Message-ID: <20140213214131.GB12409@linux.vnet.ibm.com>
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Cc: David Rientjes <rientjes@google.com>, 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,
 Wanpeng Li <liwanp@linux.vnet.ibm.com>
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On 28.01.2014 [10:34:57 -0800], 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)?
> 
> 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