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

[Christoph Lameter]

On Fri, 28 Sep 2007, Peter Zijlstra wrote:

> memory got massively fragemented, as anti-frag gets easily defeated.
> setting min_free_kbytes to 12M does seem to solve it - it forces 2 max
> order blocks to stay available, so we don't mix types. however 12M on
> 128M is rather a lot.

Yes, strict ordering would be much better. On NUMA it may be possible to 
completely forbid merging. We can fall back to other nodes if necessary. 
12M is not much on a NUMA system.

But this shows that (unsurprisingly) we may have issues on systems with a 
small amounts of memory and we may not want to use higher orders on such 
systems.

The case you got may be good to use as a testcase for the virtual 
fallback. Hmmmm... Maybe it is possible to allocate the stack as a virtual 
compound page. Got some script/code to produce that problem?
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