Intel® VTune™ Amplifier XE and Intel® VTune™ Amplifier for Systems Help

4K Aliasing

Metric Description

When an earlier (in program order) load issued after a later (in program order) store, a potential WAR (write-after-read) hazard exists. To detect such hazards, the memory order buffer (MOB) compares the low-order 12 bits of the load and store in every potential WAR hazard. If they match, the load is reissued, penalizing performance. However, as only 12 bits are compared, a WAR hazard may be detected falsely on loads and stores whose addresses are separated by a multiple of 4096 (2^12). This metric estimates the performance penalty of handling such falsely aliasing loads and stores.

Possible Issues

A significant proportion of cycles is spent dealing with false 4k aliasing between loads and stores. Use the source/assembly view to identify the aliasing loads and stores, and then adjust your data layout so that the loads and stores no longer alias.

See Also