Re: [this_cpu_xx V2 16/19] this_cpu: slub aggressive use of this_cpu operations in the hotpaths

[Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>]

* Pekka Enberg (penberg@cs.helsinki.fi) wrote:
> On Wed, 2009-06-17 at 16:33 -0400, cl@linux-foundation.org wrote:
> > Use this_cpu_* operations in the hotpath to avoid calculations of
> > kmem_cache_cpu pointer addresses.
> > 
> > It is not clear if this is always an advantage.
> > 
> > On x86 there is a tradeof: Multiple uses segment prefixes against an
> > address calculation and more register pressure.
> > 
> > On the other hand the use of prefixes is necessary if we want to use
> > Mathieus scheme for fastpaths that do not require interrupt disable.
> 
> On an unrelated note, it sure would be nice if the SLUB allocator didn't
> have to disable interrupts because then we could just get rid of the gfp
> masking there completely.
> 

The solution I had just gets rid of the irqoff for the fast path. The
slow path still needs to disable interrupts.

Mathieu

> 			Pekka
> 

-- 
Mathieu Desnoyers
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