From: Jesse Larrew <jlar...@linux.vnet.ibm.com> The SPLPAR option allows the platform to dispatch virtual processors on physical processors that, due to the variable nature of work loads, are temporarily free, thus improving the utilization of computing resources. However, SPLPAR implies inconsistent mapping of virtual to physical processors, thus defeating resource allocation software that attempts to optimize performance on platforms that implement the NUMA option.
To bridge the gap between these two options, the VPHN option maintains a substantially consistent mapping of a given virtual processor to a physical processor or set of processors within a given associativity domain. When allocating computing resources, the kernel can take advantage of this statistically consistent mapping to improve processing performance. VPHN mappings are substantially consistent but not static. For any given dispatch cycle, a best effort is made by the hypervisor to dispatch the virtual processor on a physical processor within a targeted associativity domain (the virtual processor's home node). However, if processing capacity within the home node is not available, some other physical processor is assigned to meet the processing capacity entitlement. From time to time, to optimize the total platform performance, it may be necessary for the platform to change the home node of a given virtual processor. The Virtual Processor Home Node feature addresses this by adding the H_HOME_NODE_ASSOCIATIVITY hcall to retrieve the current associativity domain information directly from the hypervisor for a given virtual processor's home node. It also exposes a set of associativity change counters in the Virtual Processor Area (VPA) of each processor to indicate when associativity changes occur. This patch set sets a timer during boot that will periodically poll the associativity change counters. When a change in associativity is detected, it retrieves the new associativity domain information via the H_HOME_NODE_ASSOCIATIVITY hcall and updates the NUMA node maps and sysfs entries accordingly. The polling mechanism is also tied into the ibm,suspend-me rtas call to stop/restart polling before/after a suspend, hibernate, migrate, or checkpoint restart operation. This patch set applies to v2.6.37-rc4 and includes the following: [PATCH 1/3] powerpc: Add VPHN firmware feature [PATCH 2/3] powerpc: Poll VPA for topology changes and update NUMA maps [PATCH 3/3] powerpc: Disable VPHN polling during a suspend operation Changes since V2: * Rebased on 2.6.37-rc4. * Rearranged work declarations and timer initializations to eliminate unnecessary function declarations. * Eliminated redundant cpumask operations in update_cpu_associativity_changes_mask(). * Eliminated unnecessary return statments from functions with void return types. * Coding-style cleanups. * Replaced del_timer() with del_timer_sync() in stop_topology_update(), and added the "vphn_enabled" flag to prevent the timer function from reinstalling itself. Signed-off-by: Jesse Larrew <jlar...@linux.vnet.ibm.com> --- arch/powerpc/include/asm/firmware.h | 3 +- arch/powerpc/include/asm/hvcall.h | 3 +- arch/powerpc/include/asm/lppaca.h | 5 +- arch/powerpc/include/asm/topology.h | 10 + arch/powerpc/kernel/rtas.c | 3 + arch/powerpc/mm/numa.c | 274 +++++++++++++++++++++++++++- arch/powerpc/platforms/pseries/firmware.c | 1 + 7 files changed, 286 insertions(+), 13 deletions(-) _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
