Re: The performance and behaviour of the anti-fragmentation related patches

Christoph Lameter
2007-03-02T17:23:52Z

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.