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Message-ID: <20140218013100.GA31998@linux.vnet.ibm.com>
Date: Mon, 17 Feb 2014 17:31:00 -0800
From: Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>
To: David Rientjes <rientjes@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Fengguang Wu <fengguang.wu@...el.com>,
David Cohen <david.a.cohen@...ux.intel.com>,
Al Viro <viro@...iv.linux.org.uk>,
Damien Ramonda <damien.ramonda@...el.com>,
Jan Kara <jack@...e.cz>, linux-mm <linux-mm@...ck.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH V5] mm readahead: Fix readahead fail for no local
memory and limit readahead pages
On 17.02.2014 [15:14:06 -0800], David Rientjes wrote:
> 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?
Sorry, I was unclear in my e-mail. I meant to modify
local_memory_node(), not first_zones_zonelist(). Well, it only needs the
following, I think?
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e3758a0..5de4337 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3650,6 +3650,8 @@ int local_memory_node(int node)
gfp_zone(GFP_KERNEL),
NULL,
&zone);
+ if (!zone)
+ return NUMA_NO_NODE;
return zone->node;
}
#endif
I think that condition should only happen during boot -- maybe even
deserving of an unlikely, but I don't think the above is considered a
hot-path. If the above isn't palatable, I can look into your suggestion
instead.
Thanks,
Nish
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