There's a bug causing NSStatusItems in MenuBar<->WindowServer to enter a continuous redraw loop after a number of hours of uptime which pins CPU at like at least 10-20%. I filed it as FB24528844

    1. WindowServer sends the app a stream of remote-context notifications (CGSDatagramReadStream::dispatchMainQueueDatagrams -> remote_context_notify).
    2. AppKit responds by rebuilding the status-bar window's tracking areas and structural regions (_NSTrackingAreaAKManager _updateStructuralRegionCreateIfNeeded / displayCycleUpdateStructuralRegions, including NSButtonCell _hasRolloverAppearance for the menu bar rollover effect).
    3. That dirties the window, so UpdateCycle/stepTransactionFlush commits a CA::Transaction to the WindowServer.
    4. Another notification arrives and the loop repeats at display refresh rate.