How much power does Visual Look Up use?

Summary

Look in the log, and Visual Look Up (VLU) on an Apple silicon Mac apparently involves a great deal of work, in both CPU cores and the neural engine (ANE). This article reports a first attempt to estimate power and energy use for a single VLU on an image. To estimate this, I measured CPU, GPU and ANE power in sampling periods of 100 ms using powermetrics, and correlated events seen there with those recorded in a log extract over the same period, obtained using LogUI. The test was performed on a Mac mini M4 Pro running macOS 15.6.1, using Preview to perform the VLU on a single image showing a small group of cattle in an upland field. Power measurements were collected from a moment immediately before opening the image, and ceased several seconds after VLU was complete. When used like this, powermetrics imposes remarkably little overhead on the CPU cores, but its sampling periods are neither exact nor identical. This makes it difficult to correlate log entries and their precise timestamps with sampling periods. While powermetrics gives power use in mW, those measurements aren’t calibrated and making assumptions about their accuracy is hazardous. Nevertheless, they remain the best estimates available. Log narrative The first step in log analysis was to identify the starting time of powermetrics sampling periods. Although execution of that command left no trace in its entries, as it has to be run with elevated privileges using sudo, its approval was obvious in entries concluding 30.677182 com.apple.opendirectoryd ODRecordVerifyPassword completed A subsequent entry at 30.688828 seconds was thus chosen as the start time for sampling periods, and all times given below as given in seconds after that time zero. The following relevant events were identified in the log extract at elapsed times given in seconds: 1.3 com.apple.VisionKit Signpost Begin: “VisionKit MAD Parse Request” 1.3 com.apple.mediaanalysis Running task VCPMADServiceImageProcessingTask 1.4 ANE started and an Obj...