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Subject: Re: kernel BUG in __cache_alloc_node at linux-2.6.git/mm/slab.c:3177!
From: Will Schmidt <will_schmidt@vnet.ibm.com>
To: Christoph Lameter <clameter@sgi.com>
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Date: Fri, 13 Oct 2006 14:53:46 -0500
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Cc: linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org
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On Fri, 2006-13-10 at 12:05 -0700, Christoph Lameter wrote:
> On Fri, 13 Oct 2006, Will Schmidt wrote:
> 
> >     Am seeing a crash on a power5 LPAR when booting the linux-2.6 git
> > tree.  It's fairly early during boot, so I've included the whole log
> > below.   This partition has 8 procs, (shared, including threads), and
> > 512M RAM.  
> 
> This looks like slab bootstrap. You are bootstrapping while having 
> zonelists build with zones that are only going to be populated later? 
> This will lead to incorrect NUMA placement of lots of slab structures on 
> bootup.

I dont think so..   but it's not an area I'm very familiar with.   one
of the other PPC folks might chime in with something here.  

> 
> Check if the patch below may cure the oops. Your memory is likely 
> still placed on the wrong numa nodes since we have to fallback from 
> the intended node.

Nope, no change with this patch.

> 
> Index: linux-2.6/mm/slab.c
> ===================================================================
> --- linux-2.6.orig/mm/slab.c	2006-10-13 11:59:55.000000000 -0700
> +++ linux-2.6/mm/slab.c	2006-10-13 12:03:15.000000000 -0700
> @@ -3154,7 +3154,8 @@ void *fallback_alloc(struct kmem_cache *
> 
>  	for (z = zonelist->zones; *z && !obj; z++)
>  		if (zone_idx(*z) <= ZONE_NORMAL &&
> -				cpuset_zone_allowed(*z, flags))
> +				cpuset_zone_allowed(*z, flags) &&
> +				(*z)->free_pages)
>  			obj = __cache_alloc_node(cache,
>  					flags | __GFP_THISNODE,
>  					zone_to_nid(*z));