Re: The performance and behaviour of the anti-fragmentation relatedpatches

[Christoph Lameter]

On Fri, 2 Mar 2007, Andrew Morton wrote:

> > Linux is *not* happy on 256GB systems.  Even on some 32GB systems
> > the swappiness setting *needs* to be tweaked before Linux will even
> > run in a reasonable way.
> 
> Please send testcases.

It is not happy if you put 256GB into one zone. We are fine with 1k nodes 
with 8GB each and a 16k page size (which reduces the number of 
page_structs to manage by a fourth). So the total memory is 8TB which is 
significantly larger than 256GB.

If we do this node/zone merging and reassign MAX_ORDER blocks to virtual 
node/zones for containers (with their own LRU etc) then this would also 
reduce the number of page_structs on the list and may make things a bit 
easier.

We would then produce the same effect as the partitioning via NUMA nodes 
on our 8TB boxes. However, then you still have a bandwidth issue since 
your 256 likely only has a single bus and all memory traffic for the 
node/zones has to go through this single bottleneck. That bottleneck does 
not exist on NUMA machines.


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