Speaker
Christopher Hollowell
(Brookhaven National Laboratory)
Description
Non-uniform memory access (NUMA) is a memory architecture for symmetric
multiprocessing (SMP) systems where each processor is directly connected
to separate memory. Indirect access to other CPU's (remote) RAM is still
possible, but such requests are slower as they must also pass through that
memory's controlling CPU. In concert with a NUMA-aware operating
system, the NUMA hardware architecture can help eliminate the memory
performance reductions generally seen in SMP systems when multiple
processors simultaneously attempt to access memory.
The x86 CPU architecture has supported NUMA for a number of years. Modern
operating systems such as Linux support NUMA-aware scheduling, where the OS
attempts to schedule a process to the CPU directly attached to the majority
of its RAM. In Linux, it is possible to further manually tune the NUMA
subsystem using the "numactl" utility. With the release of Red
Hat Enterprise Linux (RHEL) 6.3, the "numad" daemon became available in
this distribution. This daemon monitors a system's NUMA topology and utilization,
and automatically makes adjustments to optimize locality.
As the number of cores in x86 servers continues to grow, efficient
NUMA mappings of processes to CPUs/memory will become increasingly
important. This presentation gives a brief overview of NUMA, and
discusses the effects of manual tunings and numad on the performance
of the HEPSPEC06 benchmark.
Author
Christopher Hollowell
(Brookhaven National Laboratory)
Co-authors
Mr
Alexandr Zaytsev
(Brookhaven National Laboratory (US))
Costin Caramarcu
(Brookhaven National Laboratory (US))
Dr
Tony Wong
(Brookhaven National Laboratory)
William Strecker-Kellogg
(Brookhaven National Lab)
