Comment 8 for bug 1489622

Upon trying it again, I'm actually seeing the load drop down in the "steady gpe17 after boot" case. I just didn't wait long enough for the boot load spike to get out of the average. Please disregard that second half of my previous comment.

Here are some more experiments:

With processor.max_cstate=0 in boot args and without changing battery/external power state, I'm seeing a steady gpe17 interrupt count, and the 1-minute load after being booted for 5 minutes at 0.01. Upon disconnecting external power, I do not see the load jump and gpe17 remains steady.

With idle=halt in boot args and without changing battery/external power state, I'm seeing a steady gpe17 interrupt count, and the 1-minute load after being booted for 5 minutes at 0.02. Upon disconnecting external power, I do see gpe17 spin and the 1-minute load jump to about 1.50 after two minutes and perf top showing:

Samples: 21K of event 'cycles', Event count (approx.): 2163359670
Overhead Shared Object Symbol
  45.50% [kernel] [k] acpi_os_read_port
   5.73% [kernel] [k] acpi_ec_read_status.isra.4

With idle=mwait in boot args and without changing battery/external power state, I'm seeing a steady gpe17 interrupt count, and the 1-minute load after being booted for 5 minutes at 0.02. Upon disconnecting external power, I do see gpe17 spin and the 1-minute load jump to about 1.45 after two minutes and perf top showing:

Samples: 100K of event 'cycles', Event count (approx.): 7259748699
Overhead Shared Object Symbol
  34.33% [kernel] [k] acpi_os_read_port
  20.85% [kernel] [k] read_hpet
   6.56% [kernel] [k] acpi_processor_ffh_cstate_enter
   4.28% [kernel] [k] acpi_ec_read_status.isra.4

In the two cases where gpe17 is spinning, disabling it drops the load back down to about 1.0 with perf top then showing:

Samples: 127K of event 'cycles', Event count (approx.): 1193854375
Overhead Shared Object Symbol
  40.05% [kernel] [k] acpi_processor_ffh_cstate_enter
   8.25% [kernel] [k] read_hpet
   5.06% [kernel] [k] _raw_spin_lock
   2.46% [kernel] [k] acpi_os_read_port
   0.99% [kernel] [k] hpet_legacy_next_event