Performance Counter

Definitions

1. A special-purpose register built into the CPU that counts low-level hardware events such as clock cycles, instructions retired, cache hits/misses, and branch mispredictions. Tools like perf, VTune, and Instruments read these counters to produce detailed performance profiles.

   In plain English: A built-in counter on the processor chip that tallies specific events like memory lookups or instructions completed, used to diagnose speed problems.

   Example: "The performance counters showed a 30% branch misprediction rate in the sort routine — switching to a branchless comparison cut runtime in half."

Related Terms

• flame graph
• FPGA
• ASIC
• UART
• Interrupt Handler
• Clock Speed
• Register
• Branch Prediction
• Machine Instruction
• Program Counter
• RISC
• Spectre
• WebHID