cpuidle: default processor.latency_factor=2

More aggressively request deep C-states.

Note that the job of the OS is to minimize latency
impact to expected break events such as interrupts.

It is not the job of the OS to try to calculate if
the C-state will reach energy break-even.
The platform doesn't give the OS enough information
for it to make that calculation.  Thus, it is up
to the platform to decide if it is worth it to
go as deep as the OS requested it to, or if it
should internally demote to a more shallow C-state.

But the converse is not true.  The platform can not
promote into a deeper C-state than the OS requested
else it may violate latency constraints.  So it is
important that the OS be aggressive in giving the
platform permission to enter deep C-states.

Signed-off-by: Len Brown <len.brown@intel.com>

diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index 26ade1f3f5cd4f67cbd158304d42d8dd5ce95425..bc99b7b9094fac9d862d7c1d0bf5b557ce5259ed 100644 (file)
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -95,7 +95,7 @@ module_param(bm_history, uint, 0644);
 static int acpi_processor_set_power_policy(struct acpi_processor *pr);
 
 #else  /* CONFIG_CPU_IDLE */
-static unsigned int latency_factor __read_mostly = 6;
+static unsigned int latency_factor __read_mostly = 2;
 module_param(latency_factor, uint, 0644);
 #endif