Date: Mon, 17 Feb 2014 15:14:06 -0800 (PST)
From: David Rientjes <rientjes@google.com>
To: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Fengguang Wu <fengguang.wu@intel.com>,
        David Cohen <david.a.cohen@linux.intel.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Damien Ramonda <damien.ramonda@intel.com>, Jan Kara <jack@suse.cz>,
        linux-mm <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH V5] mm readahead: Fix readahead fail for no local
 memory and limit readahead pages
In-Reply-To: <20140217192803.GA14586@linux.vnet.ibm.com>
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On Mon, 17 Feb 2014, Nishanth Aravamudan wrote:

> Here is what I'm running into now:
> 
> setup_arch ->
> 	do_init_bootmem ->
> 		cpu_numa_callback ->
> 			numa_setup_cpu ->
> 				map_cpu_to_node -> 
> 					update_numa_cpu_lookup_table
> 
> Which current updates the powerpc specific numa_cpu_lookup_table. I
> would like to update that function to use set_cpu_numa_node() and
> set_cpu_numa_mem(), but local_memory_node() is not yet functional
> because build_all_zonelists is called later in start_kernel. Would it
> make sense for first_zones_zonelist() to return NUMA_NO_NODE if we
> don't have a zone?
> 

Hmm, I don't think we'll want to modify the generic first_zones_zonelist() 
for a special case that is only true during boot.  Instead, would it make 
sense to modify numa_setup_cpu() to use the generic cpu_to_node() instead 
of using a powerpc mapping and then do the set_cpu_numa_mem() after 
paging_init() when the zonelists will have been built and zones without 
present pages are properly excluded?
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