User Guide


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


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