Re: [PATCH v2] MIPS: Alchemy: fix dbdma ring destruction memory debugcheck.

[Ralf Baechle <ralf@linux-mips.org>]

On Thu, Jan 28, 2010 at 09:23:56AM +0100, Manuel Lauss wrote:

> >> This fix is only necessary with the SLAB allocator and CONFIG_DEBUG_SLAB
> >> enabled;  non-debug SLAB, SLUB do return nicely aligned addresses,
> >> debug-enabled SLUB currently panics early in the boot process.
> >
> > Queued for 2.6.34 - should this also go into 2.6.33?
> 
> 2.6.33 and .32 at least.  That code has been in there since the dawn of 2.6;
> the fact that nobody has tripped over this so far means that noone build kernels
> with slab debugging (I tripped over this while looking for something else) or
> the slab allocator behaviour changed recently.

The behaviour of the slab has been like this as long as I can remember.
Cherrypicking into the -stable branches as I'm writing this.

> > Have you considered increasing the value ARCH_KMALLOC_MINALIGN which
> > defaults to 8?  Or your own slab cache of suitable alignment?  The latter
> > is more something for frequent allocations.
> 
> I have to admit I know nothing about Linux' memory management.  Are slab
> caches not affected by the what I presume are "guard bytes" inserted into
> the memory areas when slab debug is on?

When creating a slab cache an alignment for objects allocated from this
cache can be specified.

  Ralf