linux-kernel - Re: [Bugme-new] [Bug 13690] New: nodes_clear cause hugepage unusable on non-NUMA machine

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Message-ID: <4A4E2638.9080101@kernel.org>
Date:	Fri, 03 Jul 2009 08:39:36 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Christoph Lameter <cl@...ux-foundation.org>
CC:	alex.shi@...el.com, Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	"bugzilla-daemon@...zilla.kernel.org" 
	<bugzilla-daemon@...zilla.kernel.org>,
	"bugme-daemon@...zilla.kernel.org" <bugme-daemon@...zilla.kernel.org>,
	Mel Gorman <mel@....ul.ie>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	yanmin.zhang@...el.com, tim.c.chen@...el.com
Subject: Re: [Bugme-new] [Bug 13690] New: nodes_clear cause hugepage unusable
 on non-NUMA machine

Christoph Lameter wrote:
> On Thu, 2 Jul 2009, Yinghai Lu wrote:
> 
>> Index: linux-2.6/arch/x86/mm/init_64.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/mm/init_64.c
>> +++ linux-2.6/arch/x86/mm/init_64.c
>> @@ -598,8 +598,14 @@ void __init paging_init(void)
>>
>>  	sparse_memory_present_with_active_regions(MAX_NUMNODES);
>>  	sparse_init();
>> -	/* clear the default setting with node 0 */
>> +#if MAX_NUMNODES > 1
>> +	/*
>> +	 * clear the default setting with node 0
>> +	 * note: don't clear it, node_set_state will do nothing
>> +	 *	 (aka set it back) when numa support is not compiled in
>> +	 */
>>  	nodes_clear(node_states[N_NORMAL_MEMORY]);
> 
> The problem was that nodes_clear() does not fall back to a noop on !NUMA.
> The node_set/clear_states() operations do become noops.
> 
> Could we make it more consistent by using only operations of the same
> type? F.e. Add a node_clearall_states() in include/linux/nodemask.h that
> falls back to a noop on !NUMA like the node_*_states operation?
> 
> Another options is to restore node_states[N_NORMAL_MEMORY] to its
> initial condition. See the definition of node_states in page_alloc.c.

could use node_clear_state(0, N_NORMAL_MEMORY) instead. because default one only have node 0 set in that mask.

YH
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