PATCH/RFC - 00/NN - numa: Use generic per-cpu variables for numa_*_id() In http://marc.info/?l=linux-mm&m=125683610312546&w=4 , I described a performance problem with slab and memoryless nodes that we see on some of our platforms. I proposed modifying slab to use the "effective local memory node"--the node that local mempolicy would select--as the "local" node id for slab allocation purposes. This will allow slab to cache objects from its "local memory node" on the percpu queues, effectively eliminating the problem. Christoph Lameter suggested a more general approach using the generic percpu support: define a new interface--e.g., numa_mem_id()--that returns the "effective local memory node" for the calling context [cpu]. For nodes with memory, this will == the id of the node itself. For memoryless nodes, this will be the first node in the generic [!this_node] zonelist. Christoph also suggested converting the current "numa_node_id()" interface to use the generic percpu infrastructure. x86[_64] supports a custom [arch- specific] per cpu variable implementation of numa_node_id(). Most other archs do a table lookup. This series introduces a generic percpu implementation of numa_node_id() and numa_mem_id() in separate patches based on an incomplete "starter patch" from Christoph. Both of these implementations are conditional on new respective config options. I know that new config options aren't popular, but this allows other archs to adapt to the new implementations incrementally. Additional patches provide x86_64 and ia64 arch specific changes to use the new numa_node_id() implementation, and ia64 support for the numa_mem_id() interface. Finally, I've reimplemented the "slab memoryless node 'regression' fix" patch linked above atop the new numa_mem_id() interface. Ad hoc measurements on x86_64 using: hackbench 400 process 200 2.6.32-rc5+mmotm-091101 no patch this series x86_64 avg of 40: 4.605 4.628 ~0.5% Ia64 showed ~1.2% longer time with the series applied. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
