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Subject[RFC PATCH v2 0/8] SCHED_DEADLINE freq/cpu invariance and OPP selection
Date
Hi,

v2 of the RFC set implementing frequency/cpu invariance and OPP selection for
SCHED_DEADLINE [1]. The set is based on mainline as of today (ae64f9bd1d36).

Patches high level description:

o [01-02]/08 add the necessary links to start accounting DEADLINE contribution
to OPP selection
o 03/08 it's a temporary solution to make possible (on ARM) to change
frequency for DEADLINE tasks (that would possibly delay the SCHED_FIFO
worker kthread); proper solution would be to be able to issue frequency
transition from an atomic ctx
o [04-05]/08 it's a schedutil change that copes with the fact that DEADLINE
doesn't require periodic OPP selection triggering point
o [06-07]/08 make arch_scale_{freq,cpu}_capacity() function available on !CONFIG_SMP
configurations too
o 08/08 implements frequency/cpu invariance for tasks' reservation
parameters; which basically means that we implement GRUB-PA [2]

Changes w.r.t. RFCv1:

- rebase on mainline
- return -EINVAL for user trying to use the new flag (Peter)
- s/SPECIAL/SUGOV/ in the flag name (several comments from people to
find better naming, Steve thinks SUGOV is more greppable than others)
- give worker kthread a fake (unused) bandwidth, so that if priority
inheritance is triggered we don't BUG_ON on zero runtime
- filter out fake bandwidth when computing SCHED_DEADLINE bandwidth (fix by
Claudio Scordino)

Please have a look. Feedback and comments are, as usual, more than welcome.

In case you would like to test this out:

https://github.com/jlelli/linux.git upstream/deadline/freq-rfc-v2

Best,

- Juri

[1] v0: https://lkml.org/lkml/2017/5/23/249
v1: https://lkml.org/lkml/2017/7/5/139
[2] C. Scordino, G. Lipari, A Resource Reservation Algorithm for
Power-Aware Scheduling of Periodic and Aperiodic Real-Time Tasks,
IEEE Transactions on Computers, December 2006

Juri Lelli (8):
sched/cpufreq_schedutil: make use of DEADLINE utilization signal
sched/deadline: move cpu frequency selection triggering points
sched/cpufreq_schedutil: make worker kthread be SCHED_DEADLINE
sched/cpufreq_schedutil: split utilization signals
sched/cpufreq_schedutil: always consider all CPUs when deciding next
freq
sched/sched.h: remove sd arch_scale_freq_capacity parameter
sched/sched.h: move arch_scale_{freq,cpu}_capacity outside CONFIG_SMP
sched/deadline: make bandwidth enforcement scale-invariant

include/linux/arch_topology.h | 2 +-
include/linux/sched.h | 1 +
include/linux/sched/cpufreq.h | 2 -
include/linux/sched/topology.h | 12 ++--
kernel/sched/core.c | 15 ++++-
kernel/sched/cpufreq_schedutil.c | 84 +++++++++++++++---------
kernel/sched/deadline.c | 136 ++++++++++++++++++++++++++++-----------
kernel/sched/fair.c | 4 +-
kernel/sched/sched.h | 53 +++++++++++----
9 files changed, 217 insertions(+), 92 deletions(-)

--
2.14.3

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