User Guide

Contents

LLC Hit

Metric Description

The LLC (last-level cache) is the last, and longest-latency, level in the memory hierarchy before main memory (DRAM). While LLC hits are serviced much more quickly than hits in DRAM, they can still incur a significant performance penalty. This metric also includes coherence penalties for shared data.

Possible Issues

A significant proportion of cycles is being spent on data fetches that miss in the L2 but hit in the LLC. This metric includes coherence penalties for shared data.

Tips

1. If contested accesses or data sharing are indicated as likely issues, address them first. Otherwise, consider the performance tuning applicable to an LLC-missing workload: reduce the data working set size, improve data access locality, consider blocking or partitioning your working set so that it fits into the low-level cache, or better exploit hardware prefetchers.
2. Consider using software prefetchers, but note that they can interfere with normal loads, potentially increasing latency, as well as increase pressure on the memory system.

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804