Commonly Used Metrics for Performance Analysis - Power.org

Metrics for Performance Analysis11 Memory LocationThis chapter lists and describes the events, metrics and groups needed to characterize how the data isdistributed across memory subsystems.Most users understand the term “node” to mean the same as an SMP node. But in the context of memory,“node” refers to the chips that are mounted with their associated memory onto the same board, which may bea subset of a larger SMP system. Thus, there can be more than one of these “nodes” in an SMP system.11.1Descriptions of EventsThere are 3 events, distributed across 2 event groups, needed for these POWER7 memory location metrics.This section provides more details on each event and how it is triggered.PM_DATA_FROM_DMEMData loaded from distant memoryThe processor's Data Cache was reloaded with data from a chip's memory on a different node (distant) dueto a demand load .PM_DATA_FROM_LMEMData loaded from local memoryThe processor's Data Cache was reloaded with data from the local chip's memory due to a demand load.PM_DATA_FROM_RMEMData loaded from remote memoryThe processor's Data Cache was reloaded with data from another chip's memory on the same node due to ademand load.11.2MetricsThe location of data in memory is characterized with the following metrics:MEM_LOCALITYMemory localityFormula: PM_DATA_FROM_LMEM / (PM_DATA_FROM_LMEM + PM_DATA_FROM_RMEM +PM_DATA_FROM_DMEM)LD_LMEM_PER_LD_RMEMNumber of loads from local memory per loads from remote memoryFormula: PM_DATA_FROM_LMEM / PM_DATA_FROM_RMEMLD_LMEM_PER_LD_DMEMNumber of loads from local memory per loads from distant memoryFormula: PM_DATA_FROM_LMEM / PM_DATA_FROM_DMEMLD_LMEM_PER_LD_MEMNumber of loads from local memory per loads from remote anddistant memoryFormula: PM_DATA_FROM_LMEM / (PM_DATA_FROM_DMEM + PM_DATA_FROM_RMEM)LD_RMEM_PER_LD_DMEMNumber of loads from remote memory per loads from distantmemoryFormula: PM_DATA_FROM_RMEM / PM_DATA_FROM_DMEM11.3 Event GroupsThese events are listed in Two event groups are needed to cover memory location events.Table 11-1. The relevant events are listed alphabetically by name and each row includes the name of a PMCgroup where the event can be found and a short description. The PMC group can be used with tools likehpmcount (see Section 4.2.1) to collect several events at once, minimizing the number of runs needed toCopyright ©2011 IBM Corporation Page 35 of 52