linux-kernel - [PATCH v2 0/4] sched: Instrument sched domain flags

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Date:   Tue, 16 Jun 2020 00:41:50 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, peterz@...radead.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, morten.rasmussen@....com
Subject: [PATCH v2 0/4] sched: Instrument sched domain flags

Hi,

I've repeatedly stared at an SD flag and asked myself "how should that be
set up in the domain hierarchy anyway?". I figured that if we formalize our
flags zoology a bit, we could also do some runtime assertions on them -
this is what this series is all about.

Patches
=======

The idea is to associate the flags with a metatype that describes how they
should be set in a sched domain hierarchy - details are in the comments and
commit logs. For now it's just a simple parent/children relationship
description ("if this SD has it, all its {parents, children} have it").

The good thing is that this all goes away when CONFIG_SCHED_DEBUG isn't
set. The bad thing is that replaces SD_* flags definitions with some
unsavoury macros. This is mainly because I wanted to avoid having to
duplicate work between declaring the flags and declaring their metatypes.

There's also the removal of yet another SD flag (SD_SHARE_POWERDOMAIN).

Some deltas
===========

This time around it's a slight size increase (w/o SCHED_DEBUG): 

  $ compare.sh before after vmlinux.o
  cpu_attach_domain                                         996       1000   +4
  build_sched_domains                                      4716       4728   +12

Comparing the objdumps side by side, nothing obvious stands out to me.

Revisions
=========

RFC -> v2
---------

RFC at: https://lkml.kernel.org/r/20200311183320.19186-1-valentin.schneider@arm.com

o Rebased on top of tip/sched/core
o Aligned wording of comments between flags
o Rectified some flag descriptions (Morten)
o Added removal of SD_SHARE_POWERDOMAIN (Morten)

Cheers,
Valentin

Valentin Schneider (4):
  sched/topology: Split out SD_* flags declaration to its own file
  sched/topology: Define and assign sched_domain flag metadata
  sched/topology: Verify SD_* flags setup when sched_debug is on
  arm, sched/topology: Remove SD_SHARE_POWERDOMAIN

 arch/arm/kernel/topology.c     |   2 +-
 include/linux/sched/sd_flags.h | 133 +++++++++++++++++++++++++++++++++
 include/linux/sched/topology.h |  29 +++----
 kernel/sched/topology.c        |  27 +++++--
 4 files changed, 169 insertions(+), 22 deletions(-)
 create mode 100644 include/linux/sched/sd_flags.h

--
2.27.0