User Guide

  • 2020
  • 06/18/2020
  • Public Content
Contents

Bad Speculation (Cancelled Pipeline Slots)

Metric Description

Bad Speculation represents a Pipeline Slots fraction wasted due to incorrect speculations. This includes slots used to issue uOps that do not eventually get retired and slots for which the issue-pipeline was blocked due to recovery from an earlier incorrect speculation. For example, wasted work due to mispredicted branches is categorized as a Bad Speculation category. Incorrect data speculation followed by Memory Ordering Nukes is another example.

Possible Issues

A significant proportion of pipeline slots containing useful work are being cancelled. This can be caused by mispredicting branches or by machine clears. Note that this metric value may be highlighted due to Branch Resteers issue.

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