Re: 2.6.22 -mm merge plans: slub

[Christoph Lameter]

On Wed, 2 May 2007, Andrew Morton wrote:

> > This is a sensitive piece of the kernel as you say and we better allow the 
> > running of two allocator for some time to make sure that it behaves in all 
> > load situations. The design is fundamentally different so its performance 
> > characteristics may diverge significantly and perhaps there will be corner 
> > cases for each where they do the best job.
> 
> eek.  We'd need to fix those corner cases then.  Our endgame
> here really must be rm mm/slab.c.

First we need to discover them and I doubt that mm covers much more than 
development loads. I hope we can get to a point where we have SLUB be 
the primarily allocator soon but I would expect various performance issues 
to show up.

On the other hand: I am pretty sure that SLUB can replace SLOB completely 
given SLOBs limitations and SLUBs more efficient use of space. SLOB needs 
8 bytes of overhead. SLUB needs none. We may just have to #ifdef out the 
debugging support to make the code be of similar size to SLOB too. SLOB is 
a general problem because its features are not compatible to SLAB. F.e. it 
does not support DESTROY_BY_RCU and does not do reclaim the right way etc 
etc. SLUB may turn out to be the ideal embedded slab allocator.
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