Intel® VTune™ Profiler User Guide

User Guide

Contents

Memory Bandwidth

Metric Description

This metric represents a fraction of cycles during which an application could be stalled due to approaching bandwidth limits of the main memory (DRAM). This metric does not aggregate requests from other threads/cores/sockets (see Uncore counters for that). Consider improving data locality in NUMA multi-socket systems.

Possible Issues

A significant fraction of cycles were stalled due to to approaching bandwidth limits of the main memory (DRAM).

Tips

Improve data accesses to reduce cacheline transfers from/to memory using these possible techniques:
  • Consume all bytes of each cacheline before it is evicted (for example, reorder structure elements and split non-hot ones).
  • Merge compute-limited and bandwidth-limited loops.
  • Use NUMA optimizations on a multi-socket system.
Software prefetches do not help a bandwidth-limited application.

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