The August power-related fix targets a specific wait inside FEX’s Wine support. It should not be read as a measured battery-life improvement across all emulated applications.
What the WFE change actually covers
FEX 2608, dated August 4, uses WFE while certain Wine paths wait on an atomic during thread suspension. The project describes possible power savings in this edge case, without a general battery benchmark. It also removes the deprecated FEXInterpreter binary; the replacement name is FEX.
The diagram shows the conceptual difference between repeatedly checking a condition and waiting between checks. It is not an instruction trace. In particular, it should not be interpreted as a claim that every guest PAUSE instruction or application lock now becomes this wait.
Separate correctness, responsiveness and energy
For a relevant comparison, identify an application that actually exercises the affected path. Keep the FEX build, Wine version, root filesystem, host kernel and power policy in the report. Repeat the same task and retain completion time, errors and energy consumption together.
Average power alone is ambiguous: a lower wattage can still consume more energy if the job takes substantially longer. Conversely, a short workload can finish faster without improving an unrelated idle scenario. The right question is what happened to the task and its total cost, not whether one graph went down.
What changed again in September
The 2609 notes, dated September 7, introduce an optional JIT disk cache. The developers explicitly report no implemented size limit or stale-entry removal and possible invalidation conflicts after file changes. This remains an experiment, not a universal recommendation to enable caching.
If evaluating it, distinguish a cold run from a repeated run that can reuse translated code. Track cache size and repeat after an application update; a warm-run speedup does not answer whether invalidation works correctly.
For the binary rename, inspect launchers, wrappers and binfmt configuration before upgrading. Change the command where it is explicitly named, then verify the normal launch path. Replacing a filename in a script is only part of the migration if a distribution package also owns the registration.
September 8: restrict WFE claim to Wine thread-suspension spinloops, verify FEX binary migration and add the 2609 experimental disk-cache limitations.