linux-kernel - [PATCH v6 0/4] sched: Don't trigger misfit if affinity is restricted

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Date: Tue, 20 Feb 2024 22:56:18 +0000
From: Qais Yousef <qyousef@...alina.io>
To: Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>
Cc: linux-kernel@...r.kernel.org,
	"Pierre Gondois" <Pierre.Gondois@....com>,
	Qais Yousef <qyousef@...alina.io>
Subject: [PATCH v6 0/4] sched: Don't trigger misfit if affinity is restricted

Changes since v5:

	* Remove redundant check to rq->rd->max_cpu_capacity
	* Simplify check_misfit_status() further by removing unnecessary checks.
	* Add new patch to remove no longer used rd->max_cpu_capacity
	* Add new patch to prevent misfit lb from polluting balance_interval
	  and nr_balance_failed

Changes since v4:

	* Store max_allowed_capacity in task_struct and populate it when
	  affinity changes to avoid iterating through the capacities list in the
	  fast path (Vincent)
	* Use rq->rd->max_cpu_capacity which is updated after hotplug
	  operations to check biggest allowed capacity in the system.
	* Undo the change to check_misfit_status() and improve the function to
	  avoid similar confusion in the future.
	* Split the patches differently. Export the capacity list and sort it
	  is now patch 1, handling of affinity for misfit detection is patch 2.

Changes since v3:

	* Update commit message of patch 2 to be less verbose

Changes since v2:

	* Convert access of asym_cap_list to be rcu protected
	* Add new patch to sort the list in descending order
	* Move some declarations inside affinity check block
	* Remove now redundant check against max_cpu_capacity in check_misfit_status()

Changes since v1:

	* Use asym_cap_list (thanks Dietmar) to iterate instead of iterating
	  through every cpu which Vincent was concerned about.
	* Use uclamped util to compare with capacity instead of util_fits_cpu()
	  when iterating through capcities (Dietmar).
	* Update commit log with test results to better demonstrate the problem

v1 discussion: https://lore.kernel.org/lkml/20230820203429.568884-1-qyousef@layalina.io/
v2 discussion: https://lore.kernel.org/lkml/20231212154056.626978-1-qyousef@layalina.io/
v3 discussion: https://lore.kernel.org/lkml/20231231175218.510721-1-qyousef@layalina.io/
v4 discussion: https://lore.kernel.org/lkml/20240105222014.1025040-1-qyousef@layalina.io/
v5 discussion: https://lore.kernel.org/lkml/20240205021123.2225933-1-qyousef@layalina.io/

I ended up adding the patch to prevent increasing balance_interval to the
series. The other lb issues discussed in v4 are still pending more debugging.

Thanks!

--
Qais Yousef

Qais Yousef (4):
  sched/topology: Export asym_capacity_list
  sched/fair: Check a task has a fitting cpu when updating misfit
  sched/topology: Remove max_cpu_capacity from root_domain
  sched/fair: Don't double balance_interval for migrate_misfit

 include/linux/sched.h   |  1 +
 init/init_task.c        |  1 +
 kernel/sched/fair.c     | 90 ++++++++++++++++++++++++++++++++---------
 kernel/sched/sched.h    | 16 +++++++-
 kernel/sched/topology.c | 56 +++++++++++++------------
 5 files changed, 113 insertions(+), 51 deletions(-)

-- 
2.34.1