CPU Deoptimization Project Finds Slowest x86 Instruction
A hardware researcher has created a leaderboard to measure the single instruction with the highest latency on x86 processors. The current winner, fxrstor64, took 62 seconds or 198 billion cycles to execute, restoring the state of registers used for SIMD calculations. This project aims to optimize software by identifying the slowest instructions, but its findings also raise concerns about processor efficiency.
Key points
- Christopher Domas, a hardware researcher, created the CPU Deoptimization leaderboard to measure the single instruction with the highest latency on x86 processors.
- The current winner, fxrstor64, took 62 seconds or 198 billion cycles to execute, restoring the state of registers used for SIMD calculations.
- Domas used the mmiotic tool to find a high-latency area in the internal PCIe fabric and forced the CPU to load a 512-byte state from MMIO, processing all 512 bytes as slow as possible.
- The project aims to optimize software by identifying the slowest instructions, but its findings also raise concerns about processor efficiency and the potential for optimization trade-offs.
A hardware researcher has taken an unconventional approach to optimizing software performance on x86 processors. Christopher Domas, a well-known expert in the field, has created the CPU Deoptimization leaderboard to measure the single instruction with the highest latency on these processors.
The leaderboard currently features fxrstor64, an instruction that took an astonishing 62 seconds or 198 billion cycles to execute. This instruction restores the state of registers used for SIMD calculations to a 512-byte memory location. To achieve this record-breaking latency, Domas used a combination of tools and techniques, including the mmiotic tool to find a high-latency area in the internal PCIe fabric and forcing the CPU to load a 512-byte state from MMIO.
The project's goal is to optimize software by identifying the slowest instructions and optimizing them for better performance. However, the findings also raise concerns about processor efficiency and the potential for optimization trade-offs. As processors become increasingly complex, it's essential to understand how they work and how to optimize them for better performance.
The CPU Deoptimization leaderboard is an interesting example of how researchers are pushing the boundaries of what's possible with x86 processors. While the findings may not have immediate practical applications, they contribute to our understanding of processor efficiency and optimization techniques.
Sources
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