2023-11-30 16:13:50

by Valentin Schneider

[permalink] [raw]
Subject: [RFC PATCH 0/2] sched/fair: Delay throttling to kernel exit

Hi folks

I apologize for the one-big-patch-to-rule-them-all, I tried splitting but I
couldn't get to anything that made sense, so it's one big patch and a small
follow-up.

TL;DR of what I'd like to hear about:
o Is there interest in getting this in for !PREEMPT_RT reasons?
o Any ideas on how to make cgroup migration less horrible so we can fully pop
out the throttled cfs_rq se's?

Survives a good hour of my testing below on a 4-CPU QEMU system, but I expect
the throttled clocks & PELT to be busted.

Testing
=======

setup
+++++
mount -t cgroup -o cpu none /root/cpu

mkdir /root/cpu/cg0
echo 10000 > /root/cpu/cg0/cpu.cfs_period_us
echo 1000 > /root/cpu/cg0/cpu.cfs_quota_us

mkdir /root/cpu/cg0/cg00
mkdir /root/cpu/cg0/cg01

mkdir /root/cpu/cg0/cg00/cg000
mkdir /root/cpu/cg0/cg00/cg001

read.sh
+++++++
while true; do cat /sys/devices/system/cpu/smt/active &>/dev/null; done

repro.sh
++++++++
spawn() {
./read.sh &
PID=$!
echo "Tracing PID${PID}"
echo $PID > $1
}

spawn cpu/cg0/tasks
spawn cpu/cg0/tasks
spawn cpu/cg0/tasks
spawn cpu/cg0/tasks

spawn cpu/cg0/cg01/tasks

spawn cpu/cg0/cg00/cg000/tasks
spawn cpu/cg0/cg00/cg001/tasks

sleep 1

kill $(jobs -p)

Valentin Schneider (2):
sched/fair: Only throttle CFS tasks on return to userspace
sched/fair: Repurpose cfs_rq_throttled()

include/linux/sched.h | 2 +
kernel/sched/core.c | 6 +-
kernel/sched/debug.c | 4 +-
kernel/sched/fair.c | 296 +++++++++++++++++++++++++++---------------
kernel/sched/sched.h | 8 +-
5 files changed, 204 insertions(+), 112 deletions(-)

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2.41.0