Messages in this thread | | | From | Qais Yousef <> | Subject | [PATCH v2 0/9] Fix relationship between uclamp and fits_capacity() | Date | Thu, 4 Aug 2022 15:36:00 +0100 |
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Relationship between uclamp and fits_capacity() is currently broken. Mostly due to how uclamp should interact with migration margin and capacity pressure. But also due not all users were converted to consider uclamp before calling fits_capacity(). Namely cpu_overutilized().
The meat of the series is patch 1 where we introduce a new function, util_fits_cpu(), that takes uclamp into account. The new function should replace all call sits to fits_capacity(), which what subsequent patches do. Except for patch 7 where we fix handling of early exit condition in find_energy_efficient_cpu(AKA feec()) that must be uclamp aware too.
util_fits_cpu() will revert back to a simple call to fits_capacity() if uclamp is not being used on the system.
Last two patches still need testing and verification, but they address the various thermal handling issues raised in v1. We can re-order the patches, but added at the end to facilitate review at this stage. Hope the approach and the logic make sense.
I'll be on holidays, so if I don't respond to review comments fast enough, apologies in advance.
Changes in v2:
* use uclamp_rq_is_idle() in uclamp_rq_util_with() (Xuewen)
* Simplify logic in update_sg_wakeup_stats() when converting task_fits_cpu() (Vincent)
* Better handling of thermal pressure (Vincent)
- We consider thermal pressure for uclamp_min in patch 1 - 2 new patches to handle capacity inversion which improves handling when:
+ There're multiple big cpus on separate perf domains. + A task is boosted by uclamp_min and inspite of thermal pressure, the big cpu is still the best placement.
e.g: p0->util_avg = 300, p0->uclamp_min = 1024
This task should stay on big CPU until thermal pressure is in capacity inversion.
v1 discussion: https://lore.kernel.org/lkml/20220629194632.1117723-1-qais.yousef@arm.com/
Thanks for all reviewers on v1!
Qais Yousef (9): sched/uclamp: Fix relationship between uclamp and migration margin sched/uclamp: Make task_fits_capacity() use util_fits_cpu() sched/uclamp: Fix fits_capacity() check in feec() sched/uclamp: Make select_idle_capacity() use util_fits_cpu() sched/uclamp: Make asym_fits_capacity() use util_fits_cpu() sched/uclamp: Make cpu_overutilized() use util_fits_cpu() sched/uclamp: Cater for uclamp in find_energy_efficient_cpu()'s early exit condition sched/fair: Detect capacity inversion sched/fair: Consider capacity inversion in util_fits_cpu()
kernel/sched/core.c | 10 +- kernel/sched/fair.c | 290 ++++++++++++++++++++++++++++++++++++++----- kernel/sched/sched.h | 70 ++++++++++- 3 files changed, 329 insertions(+), 41 deletions(-)
-- 2.25.1
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