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 metaflags that describes how they
should be set in a sched domain hierarchy ("if this SD has it, all its {parents,
children} have it") or how they behave wrt degeneration - details are in the
comments and commit logs.
The good thing is that the debugging bits go away when CONFIG_SCHED_DEBUG isn't
set. The bad thing is that this 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 metaflags.
o Patches 1-2 set up the SD flag definition groundwork
o Patch 3 enables the hierarchy debugging
o Patch 4 is a derelict SD flag removal
o Patches 5-7 tweak the SD degeneration to leverage metaflags as well (suggested
by Peter).
Note that this builds a compile-time mask using the single most horrendous
macro I have ever presented to the public eye. It might end up being much
better to explicitely build the mask in topology.h, but to be honest I felt
like I had to show that monster around out of morbid fascination.
Revisions
=========
v2 -> v3
--------
o Reworded comment for SD_OVERLAP (it's about the groups, not the domains)
o Added more flags to the SD degeneration mask
o Added generation of an SD flag mask for the degeneration functions (Peter)
RFC -> v2
---------
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)
Valentin Schneider (7):
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
sched/topology: Add more flags to the SD degeneration mask
sched/topology: Introduce SD metaflag for flags needing > 1 groups
sched/topology: Use prebuilt SD flag degeneration mask
arch/arm/kernel/topology.c | 2 +-
include/linux/sched/sd_flags.h | 153 +++++++++++++++++++++++++++++++++
include/linux/sched/topology.h | 36 +++++---
kernel/sched/topology.c | 40 +++++----
4 files changed, 197 insertions(+), 34 deletions(-)
create mode 100644 include/linux/sched/sd_flags.h
--
2.27.0
