0/7 xen: Add basic NUMA support

The patchset will add basic NUMA support to Xen (hypervisor only). We borrowed from Linux support for NUMA SRAT table parsing, discontiguous memory tracking (mem chunks), and cpu support (node_to_cpumask etc).

The hypervisor parses the SRAT tables and constructs mappings for each node such as node to cpu mappings and memory range to node mappings.

Using this information, we also modified the page allocator to provide a simple NUMA-aware API. The modified allocator will attempt to find pages local to the cpu where possible, but will fall back on using memory that is of the requested size rather than fragmenting larger contiguous chunks to find local pages. We expect to tune this algorithm in the future after further study.

We also modified Xen's increase_reservation memory op to balance memory distribution across the vcpus in use by a domain. Relying on previous patches which have already been committed to xen-unstable, a guest can be constructed such that its entire memory is contained within a specific NUMA node.

We've added a keyhandler for exposing some of the NUMA-related information and statistics that pertain to the hypervisor.

We export NUMA system information via the physinfo hypercall. This information provides cpu/memory topology and configuration information gleaned from the SRAT tables to userspace applications. Currently, xend doesn't leverage any of the information automatically but we intend to do so in the future.

We've integrated in NUMA information into xentrace so we can track various points such as page allocator hits and misses as well as other information. In the process of implementing the trace, we also fixed some incorrect assumptions about the symmetry of NUMA systems w.r.t the sockets_per_node value. Details are available a later email with the patch.

These patches have been tested on several IBM NUMA and non-NUMA systems:

NUMA-aware systems:

IBM Dual Opteron:  2 Node,  2 CPU,  4GB 
IBM x445        :  4 Node, 32 CPU, 32GB 
IBM x460        :  1 Node,  8 CPU, 16GB
IBM x460        :  2 Node, 32 CPU, 32GB

Non NUMA-aware systems (i.e, no SRAT tables):

IBM Dual Xeon   :  1 Node,  2 CPU,  2GB 
IBM P4          :  1 Node,  1 CPU,  1GB

We look forward to your review of the patches for acceptance.

Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253   T/L: 678-9253
[email protected]