sched/uclamp: Make cpu_overutilized() use util_fits_cpu()
authorQais Yousef <qais.yousef@arm.com>
Thu, 4 Aug 2022 14:36:06 +0000 (15:36 +0100)
committerPeter Zijlstra <peterz@infradead.org>
Thu, 27 Oct 2022 09:01:19 +0000 (11:01 +0200)
commitc56ab1b3506ba0e7a872509964b100912bde165d
tree8d3ab721db07560dd9ae6df27db359d7094a69eb
parenta2e7f03ed28fce26c78b985f87913b6ce3accf9d
sched/uclamp: Make cpu_overutilized() use util_fits_cpu()

So that it is now uclamp aware.

This fixes a major problem of busy tasks capped with UCLAMP_MAX keeping
the system in overutilized state which disables EAS and leads to wasting
energy in the long run.

Without this patch running a busy background activity like JIT
compilation on Pixel 6 causes the system to be in overutilized state
74.5% of the time.

With this patch this goes down to  9.79%.

It also fixes another problem when long running tasks that have their
UCLAMP_MIN changed while running such that they need to upmigrate to
honour the new UCLAMP_MIN value. The upmigration doesn't get triggered
because overutilized state never gets set in this state, hence misfit
migration never happens at tick in this case until the task wakes up
again.

Fixes: af24bde8df202 ("sched/uclamp: Add uclamp support to energy_compute()")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220804143609.515789-7-qais.yousef@arm.com
kernel/sched/fair.c