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Keir Fraser
b501c6cfa8
the "guest to a single NUMA node" constrain algorithm does not work well when we do ballooning. Ballooning and NUMA don't play together anyway, as Dom0 and thus ballooning is not NUMA aware, I am working on this but it will not be ready for the Xen 4.0 release window. The usual ballooning situation will result in an empty candidate list, as no node has enough free memory to host the guest. In this case the code will simply pick the first node: again and again, because all nodes without enough memory will be ultimately penalized with the same maxint value (regardless of the actual load). The attached patch will change this to use a relative penalty in case of not-enough memory, so that low-load low-memory nodes will be used at one point. A half loaded node has shown to be a good value, as an unbalanced system is much worse than non-local memory access for guests. Regardless of that you should restrict the Dom0 on a NUMA system to a reasonable memory size, so that ballooning is not necessary most of the time. In this case the guest's memory will be NUMA local. Signed-off-by: Andre Przywara <andre.przywara@amd.com>
The file test.py here is from the Zope project, and is Copyright (c) 2001, 2002 Zope Corporation and Contributors. This file is released under the Zope Public License, version 2.0, a copy of which is in the file ZPL-2.0.