Re: [RFC] Make the slab allocator observe NUMA policies

[Andi Kleen <ak@suse.de>]

On Thursday 10 November 2005 23:04, Christoph Lameter wrote:
> Currently the slab allocator simply allocates slabs from the current node
> or from the node indicated in kmalloc_node().
>
> This change came about with the NUMA slab allocator changes in 2.6.14.
> Before 2.6.14 the slab allocator was obeying memory policies in the sense
> that the pages were allocated in the policy context of the currently
> executing process (which could allocate a page according to MPOL_INTERLEAVE
> for one process and then use the free entries in that page for another
> process that did not have this policy set).
>
> The following patch adds NUMA memory policy support. This means that the
> slab entries (and therefore also the pages containing them) will be
> allocated according to memory policy.

You're adding a check and potential cache line miss to a really really hot 
path. I would prefer  it to do the policy check only in the slower path of 
slab that gets memory from the backing page allocator. While not 100% exact 
this should be  good enough for just spreading memory around during 
initialization. And I cannot really think of any other uses of this.

-Andi

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