linux-kernel - Re: [PATCH] x86: fix system without memory on node0

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Date:	Wed, 13 May 2009 10:43:48 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Jack Steiner <steiner@....com>
CC:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Andi Kleen <andi@...stfloor.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Mike Travis <travis@....com>
Subject: Re: [PATCH] x86: fix system without memory on node0

Jack Steiner wrote:
> On Tue, May 12, 2009 at 06:34:31PM -0700, Yinghai Lu wrote:
>> Jack found that crash with doesn't have memory on node0.
>>
>> it turns out with per_cpu changeset, node_number for BSP will be alway 0,
>> and it is consistent to cpu_to_node() that is to near node already.
>> aka when numa_set_node() for node0 is called early before per_cpu area is
>> setup
>>
>> try to set the node_number for boot cpu, after we get per_cpu area setup.
>>
>> [ Impact: fix crashing on memoryless node 0]
>>
>> Reported-by: Jack Steiner <steiner@....com>
>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>>
>> ---
>>  arch/x86/kernel/setup_percpu.c |    8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> Index: linux-2.6/arch/x86/kernel/setup_percpu.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/kernel/setup_percpu.c
>> +++ linux-2.6/arch/x86/kernel/setup_percpu.c
>> @@ -423,6 +423,14 @@ void __init setup_per_cpu_areas(void)
>>  	early_per_cpu_ptr(x86_cpu_to_node_map) = NULL;
>>  #endif
>>  
>> +#if defined(CONFIG_X86_64) && defined(CONFIG_NUMA)
>> +	/*
>> +	 * make sure boot cpu node_number is right, when boot cpu is on the
>> +	 * node that doesn't have mem installed
>> +	 */
>> +	per_cpu(node_number, boot_cpu_id) = cpu_to_node(boot_cpu_id);
>> +#endif
>> +
>>  	/* Setup node to cpumask map */
>>  	setup_node_to_cpumask_map();
>>  
> 
> With the patch above PLUS the patch below, I verified that all of our strange
> configurations boot to shell prompt & run simple commands. There are certainly
> some corner cases that have not been tested.
> 
> Note that both patches are required. The system panics in early boot if either
> patch is omitted.
> 
> ---
> 
> 
> Ignore offline nodes when building the zone lists. This
> fix is needed to support configurations that hax PXMs with
> cpus but no memory.
> 
> 
> Signed-off-by: Jack Steiner <steiner@....com>
> 
> 
> ---
>  mm/page_alloc.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> Index: linux/mm/page_alloc.c
> ===================================================================
> --- linux.orig/mm/page_alloc.c	2009-05-12 17:06:59.000000000 -0500
> +++ linux/mm/page_alloc.c	2009-05-13 09:54:09.000000000 -0500
> @@ -2370,6 +2370,8 @@ static void build_zonelists(pg_data_t *p
>  		 * If another node is sufficiently far away then it is better
>  		 * to reclaim pages in a zone before going off node.
>  		 */
> +		if (!node_online(node))
> +			continue;
>  		if (distance > RECLAIM_DISTANCE)
>  			zone_reclaim_mode = 1;
>  

that means that node_states[N_HIGH_MEMORY] is still not right.

and it should be done by
/*
 * early_calculate_totalpages()
 * Sum pages in active regions for movable zone.
 * Populate N_HIGH_MEMORY for calculating usable_nodes.
 */
static unsigned long __init early_calculate_totalpages(void)
{
        int i;
        unsigned long totalpages = 0;

        for (i = 0; i < nr_nodemap_entries; i++) {
                unsigned long pages = early_node_map[i].end_pfn -
                                                early_node_map[i].start_pfn;
                totalpages += pages;
                if (pages)
                        node_set_state(early_node_map[i].nid, N_HIGH_MEMORY);
        }
        return totalpages;
}
     

also

void __init free_area_init_nodes(unsigned long *max_zone_pfn)
...



somehow that is broken?

YH
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