sched: kill sched_use_walt_cpu_{task_}util sysctl knobs
sched_use_walt_cpu_{task_}util sysctl knobs are used to control
runtime whether to use WALT signals (cumulative_runnable_avg/
ravg.demand) or PELT signal (util_avg) for task and cpu utilization
for task placement and frequency guidance.
But there is a subtle impact with these tunables when we frequently
toggle them. When sched_use_walt_cpu_util set to 0, and hotplugging
the cpu makes sg_cpu() members reset to 0, which sets sg_cpu.walt_load
to 0, but the sg_policy->last_ws never reset to zero. When the knob is
set back to 1 exactly after load is queried but before sugov_calc_avg_cap()
is called, which would compare walt_load->ws (= 0) against the stale
value of sg_policy->last_ws and hits BUG_ON().
When walt is enabled, we always use walt signals for task placement and
frequency guidance. So kill these sysctl knobs.
Change-Id: Id7eea8aa36fcfc33539aa3887c512a70a2414fc0
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>
1 file changed