tree 8ccdae0e126ed5c4de1a06b901b89cb2dc709bfc
parent 420634ee8d613887d52c50cbf90956845934e3e8
author Junjie Wu <junjiew@codeaurora.org> 1429300116 -0700
committer Stephen Boyd <sboyd@codeaurora.org> 1490037372 -0700

cpufreq: interactive: Replace per-cpu timer with per-policy timer

Interactive governor currently uses per-cpu timer to evaluate each
CPU's frequency. For policies that manages multiples CPUs, each CPU
runs its own algorithm to decide its frequency and then final result
is aggregated in speedchange task. This implementation has a few
drawbacks.

Due to the use of deferrable timers, timers between CPUs can be easily
misaligned. If a load migrates from CPU A to CPU B, there exists a gap
where CPU A could have dropped its frequency vote yet CPU B hasn't
seen the demand to ramp up its vote. This would result in an incorrect
drop in policy frequency which is harmful for performance.

In addition, for CPU waking up in middle of a window, the timestamps
it takes will not be aligned with jiffy boundaries, and thus when next
time timer fires, it could incorrectly prevent frequency ramp up/down
for one more window.

Change-Id: Ia82c7b0cff5bb1ea165fb83fbb7a5546ea7d0396
[junjiew@codeaurora.org: Resolved merge conflicts. ]
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>