Intel® 64 and IA-32 Architectures Optimization Reference Manual

USING PERFORMANCE MONITORING EVENTS8. L2 Instruction Cache Line Miss Rate: L2_IFETCH.SELF.I_STATE /INST_RETIRED.ANYL2 Instruction Cache Line Miss Rate higher than zero indicates instruction cache linemisses from the L2 cache may have a noticeable performance impact of programperformance.B.7.2.2Branching and Front-end9. BACLEAR Performance Impact: 7 * BACLEARS / CPU_CLK_UNHALTED.COREA high value for BACLEAR Performance Impact ratio usually indicates that the codehas many branches such that they cannot be consumed by the Branch PredictionUnit.10. Taken Branch Bubble: (BR_TKN_BUBBLE_1+BR_TKN_BUBBLE_2) /CPU_CLK_UNHALTED.COREA high value for Taken Branch Bubble ratio indicates that the code contains manytaken branches coming one after the other and cause bubbles in the front-end. Thismay affect performance only if it is not covered by execution latencies and stalls laterin the pipe.B.7.2.3Stack Pointer Tracker11. ESP Synchronization: ESP.SYNCH / ESP.ADDITIONSThe ESP Synchronization ratio calculates the ratio of ESP explicit use (for example byload or store instruction) and implicit uses (for example by PUSH or POP instruction).The expected ratio value is 0.2 or lower. If the ratio is higher, consider rearrangingyour code to avoid ESP synchronization events.B.7.2.4Macro-fusion12. Macro-Fusion: UOPS_RETIRED.MACRO_FUSION / INST_RETIRED.ANYThe Macro-Fusion ratio calculates how many of the retired instructions were fused toa single micro-op. You may find this ratio is high for a 32-bit binary executable butsignificantly lower for the equivalent 64-bit binary, and the 64-bit binary performsslower than the 32-bit binary. A possible reason is the 32-bit binary benefited frommacro-fusion significantly.B.7.2.5Length Changing Prefix (LCP) Stalls13. LCP Delays Detected: ILD_STALL / CPU_CLK_UNHALTED.COREA high value of the LCP Delays Detected ratio indicates that many Length ChangingPrefix (LCP) delays occur in the measured code.B-52