Intel® 64 and IA-32 Architectures Optimization Reference Manual

USING PERFORMANCE MONITORING EVENTSB.4 USING PERFORMANCE METRICS WITH HYPER-THREADING TECHNOLOGYOn Intel Xeon processors that support HT Technology, the performance metrics listedin Tables B-1 through B-7 may be qualified to associate the counts with a specificlogical processor, provided the relevant performance monitoring events supportsqualification by logical processor. Within the subset of those performance metrics thatsupport qualification by logical processors, some of them can be programmed withparallel ESCRs and CCCRs to collect separate counts for each logical processor simultaneously.For some metrics, qualification by logical processor is supported but thereis not sufficient number of MSRs for simultaneous counting of the same metric on bothlogical processors. In both cases, it is also possible to program the relevant ESCR fora performance metric that supports qualification by logical processor to producecounts that are, typically, the sum of contributions from both logical processors.A number of performance metrics are based on performance monitoring events thatdo not support qualification by logical processor. Any attempts to program the relevantESCRs to qualify counts by logical processor will not produce different results.The results obtained in this manner should not be summed together.The performance metrics listed in Tables B-1 through B-7 fall into three categories:• Logical processor specific and supporting parallel counting• Logical processor specific but constrained by ESCR limitations• Logical processor independent and not supporting parallel countingTable B-11 lists performance metrics in the first and second category. Table B-12 listsperformance metrics in the third category.There are four specific performance metrics related to the trace cache that areexceptions to the three categories above. They are:• Logical Processor 0 Deliver Mode• Logical Processor 1 Deliver Mode• Logical Processor 0 Build Mode• Logical Processor 0 Build ModeEach of these four metrics cannot be qualified by programming bit 0 to 4 in therespective ESCR. However, it is possible and useful to collect two of these fourmetrics simultaneously.B-39