#!/usr/bin/env bash

TOTAL_CORES='0-7'
HOST_CORES='0-1'            # Cores reserved for host
HOST_CORES_MASK=C0             # 0-1,6-7, bitmask 0b000011000011
VIRT_CORES='2-7'           # Cores reserved for virtual machine(s)

# Stretch package contains an old version of cset which doesn't work (or never worked)
#cset set -c $TOTAL_CORES -s machine.slice
#cset shield --kthread on --cpu $VIRT_CORES
# Reduce VM jitter: https://www.kernel.org/doc/Documentation/kernel-per-CPU-kthreads.txt
echo 3 > /proc/sys/vm/drop_caches
echo 1 > /proc/sys/vm/compact_memory
# the kernel's dirty page writeback mechanism uses kthread workers. They introduce
# massive arbitrary latencies when doing disk writes on the host and aren't
# migrated by cset. Restrict the workqueue to use only cpu 0.
echo $HOST_CORES_MASK > /sys/bus/workqueue/devices/writeback/cpumask
echo $HOST_CORES_MASK > /sys/devices/virtual/workqueue/cpumask
echo "C0" | tee /sys/devices/virtual/workqueue/*/cpumask
# THP can allegedly result in jitter. Better keep it off.
echo never > /sys/kernel/mm/transparent_hugepage/enabled
# Force P-states to P0
echo "Setting governor on all cores:"
echo performance | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
echo 0 > /sys/bus/workqueue/devices/writeback/numa
echo 0 > /proc/sys/kernel/watchdog
echo 300 > /proc/sys/vm/stat_interval