Re: 2.6.22 -mm merge plans: slub

[Hugh Dickins]

On Thu, 3 May 2007, Andrew Morton wrote:
> On Wed, 2 May 2007 10:25:47 -0700 (PDT) Christoph Lameter <clameter@xxxxxxx> wrote:
> 
> > +config ARCH_USES_SLAB_PAGE_STRUCT
> > +	bool
> > +	default y
> > +	depends on SPLIT_PTLOCK_CPUS <= NR_CPUS
> > +
> 
> That all seems to work as intended.
> 
> However with NR_CPUS=8 SPLIT_PTLOCK_CPUS=4, enabling SLUB=y crashes the
> machine early in boot.  

I thought that if that worked as intended, you wouldn't even
get the chance to choose SLUB=y?  That was how it was working
for me (but I realize I didn't try more than make oldconfig).

> 
> Too early for netconsole, no serial console.  Wedges up uselessly with
> CONFIG_XMON=n, does mysterious repeated uncontrollable exceptions with
> CONFIG_XMON=y.  This is all fairly typical for a powerpc/G5 crash :(
> 
> However I was able to glimpse some stuff as it flew past.  Crash started in
> flush_old_exec and ended in pgtable_free_tlb -> kmem_cache_free.  I don't know
> how to do better than that I'm afraid, unless I'm to hunt down a PCIE serial
> card, perhaps.

That sounds like what happens when SLUB's pagestruct use meets
SPLIT_PTLOCK's pagestruct use.  Does your .config really show
CONFIG_SLUB=y together with CONFIG_ARCH_USES_SLAB_PAGE_STRUCT=y?

Hugh
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