linux-kernel - Re: [PATCH 1/3] Slab infrastructure for array operations

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Date:	Wed, 11 Feb 2015 12:47:41 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	David Rientjes <rientjes@...gle.com>
cc:	akpm@...uxfoundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, penberg@...nel.org, iamjoonsoo@....com,
	Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH 1/3] Slab infrastructure for array operations

On Tue, 10 Feb 2015, David Rientjes wrote:

> > +int kmem_cache_alloc_array(struct kmem_cache *s,
> > +		gfp_t flags, size_t nr, void **p)
> > +{
> > +	int i = 0;
> > +
> > +#ifdef _HAVE_SLAB_ALLOCATOR_ARRAY_OPERATIONS
> > +	/*

...

> > +		i += slab_array_alloc_from_local(s, nr - i, p + i);
> > +
> > +#endif
>
> This patch is referencing functions that don't exist and can do so since
> it's not compiled, but I think this belongs in the next patch.  I also
> think that this particular implementation may be slub-specific so I would
> have expected just a call to an allocator-defined
> __kmem_cache_alloc_array() here with i = __kmem_cache_alloc_array().

The implementation is generic and can be used in the same way for SLAB.
SLOB does not have these types of object though.

> return 0 instead of using _HAVE_SLAB_ALLOCATOR_ARRAY_OPERATIONS at all.

Ok that is a good idea. I'll just drop that macro and have all allocators
provide dummy functions.

> > +#ifndef _HAVE_SLAB_ALLOCATOR_ARRAY_OPERATIONS
> > +void kmem_cache_free_array(struct kmem_cache *s, size_t nr, void **p)
> > +{
> > +	__kmem_cache_free_array(s, nr, p);
> > +}
> > +EXPORT_SYMBOL(kmem_cache_free_array);
> > +#endif
> > +
>
> Hmm, not sure why the allocator would be required to do the
> EXPORT_SYMBOL() if it defines kmem_cache_free_array() itself.  This

Keeping the EXPORT with the definition is the custom as far as I could
tell.
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