sched/fair: Rename cfs_rq::avg_vruntime to ::sum_w_vruntime, and helper functions

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[ Upstream commit dcbc9d3f0e ]

The ::avg_vruntime field is a  misnomer: it says it's an
'average vruntime', but in reality it's the momentary sum
of the weighted vruntimes of all queued tasks, which is
at least a division away from being an average.

This is clear from comments about the math of fair scheduling:

    * \Sum (v_i - v0) * w_i := cfs_rq->avg_vruntime

This confusion is increased by the cfs_avg_vruntime() function,
which does perform the division and returns a true average.

The sum of all weighted vruntimes should be named thusly,
so rename the field to ::sum_w_vruntime. (As arguably
::sum_weighted_vruntime would be a bit of a mouthful.)

Understanding the scheduler is hard enough already, without
extra layers of obfuscated naming. ;-)

Also rename related helper functions:

  sum_vruntime_add()    => sum_w_vruntime_add()
  sum_vruntime_sub()    => sum_w_vruntime_sub()
  sum_vruntime_update() => sum_w_vruntime_update()

With the notable exception of cfs_avg_vruntime(), which
was named accurately.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://patch.msgid.link/20251201064647.1851919-7-mingo@kernel.org
Stable-dep-of: b3d99f43c7 ("sched/fair: Fix zero_vruntime tracking")
Signed-off-by: Sasha Levin <sashal@kernel.org>

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This commit is contained in:

Ingo Molnar 2025-12-02 16:09:23 +01:00 • committed by Sasha Levin

parent 50890a9a01

commit 028084eca1

2 changed files with 14 additions and 14 deletions

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kernel/sched/fair.c

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kernel/sched/sched.h

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