On Wed, 2 May 2007, Christoph Lameter wrote:
> On Wed, 2 May 2007, Hugh Dickins wrote:
>
> > I presume the answer is just to extend your quicklist work to
> > powerpc's lowest level of pagetables. The only other architecture
> > which is using kmem_cache for them is arm26, which has
> > "#error SMP is not supported", so won't be giving this problem.
>
> In the meantime we would need something like this to disable SLUB in this
> particular configuration. Note that I have not tested this and the <= for
> the comparision with SPLIT_PTLOCK_CPUS may not work (Never seen such a
> construct in a Kconfig file but it is needed here).
I'm astonished and impressed, both with Kconfig and your use of it:
that does seem to work. Though I don't dare go so far as to give
the patch an ack, and don't like this way out at all. It needs a
proper (quicklist) solution, and by the time that solution comes
along, all the powerpc people will have CONFIG_SLAB=y in their
.config, and "make oldconfig" will just perpetuate that status quo,
instead of the switching over to CONFIG_SLUB=y. I think. Unless
we keep changing the config option names, or go through a phase
with no option.
I'd much rather be testing a quicklist patch:
I'd better give that a try.
Hugh
>
>
>
> PowerPC: Disable SLUB for configurations in which slab page structs are modified
>
> PowerPC uses the slab allocator to manage the lowest level of the page table.
> In high cpu configurations we also use the page struct to split the page
> table lock. Disallow the selection of SLUB for that case.
>
> [Not tested: I am not familiar with powerpc build procedures etc]
>
> Signed-off-by: Christoph Lameter <[email protected]>
>
> Index: linux-2.6.21-rc7-mm2/arch/powerpc/Kconfig
> ===================================================================
> --- linux-2.6.21-rc7-mm2.orig/arch/powerpc/Kconfig 2007-05-02 10:07:34.000000000 -0700
> +++ linux-2.6.21-rc7-mm2/arch/powerpc/Kconfig 2007-05-02 10:13:37.000000000 -0700
> @@ -117,6 +117,19 @@ config GENERIC_BUG
> default y
> depends on BUG
>
> +#
> +# Powerpc uses the slab allocator to manage its ptes and the
> +# page structs of ptes are used for splitting the page table
> +# lock for configurations supporting more than SPLIT_PTLOCK_CPUS.
> +#
> +# In that special configuration the page structs of slabs are modified.
> +# This setting disables the selection of SLUB as a slab allocator.
> +#
> +config ARCH_USES_SLAB_PAGE_STRUCT
> + bool
> + default y
> + depends on SPLIT_PTLOCK_CPUS <= NR_CPUS
> +
> config DEFAULT_UIMAGE
> bool
> help
-
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