Re: [15/17] SLUB: Support virtual fallback via SLAB_VFALLBACK

[Christoph Lameter]

On Sat, 29 Sep 2007, Andrew Morton wrote:

> > atomic allocations. And with SLUB using higher order pages, atomic !0
> > order allocations will be very very common.
> 
> Oh OK.
> 
> I thought we'd already fixed slub so that it didn't do that.  Maybe that
> fix is in -mm but I don't think so.
> 
> Trying to do atomic order-1 allocations on behalf of arbitray slab caches
> just won't fly - this is a significant degradation in kernel reliability,
> as you've very easily demonstrated.

Ummm... SLAB also does order 1 allocations. We have always done them.

See mm/slab.c

/*
 * Do not go above this order unless 0 objects fit into the slab.
 */
#define BREAK_GFP_ORDER_HI      1
#define BREAK_GFP_ORDER_LO      0
static int slab_break_gfp_order = BREAK_GFP_ORDER_LO;

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