It’s been reported in these tickets on the bugtracker (https://dev.haiku-os.org/ticket/19602) (https://dev.haiku-os.org/ticket/20196) and on this thread: https://discuss.haiku-os.org/t/increased-processor-load-with-kernel-team-at-acpi-task-on-hrev59759/19334/10
Several people including myself are experiencing the issue. It’s appears to be due to the ACPI related changes in hrev59869 by the look of it.