From d20fb866de5bac450002eb7a8495449055b1ca06 Mon Sep 17 00:00:00 2001
From: Josh Lay <me@jlay.io>
Date: Sat, 4 Apr 2020 20:50:48 -0500
Subject: [PATCH] add VM start/CPU isolation script

---
 start-win10 | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100755 start-win10

diff --git a/start-win10 b/start-win10
new file mode 100755
index 0000000..0fde060
--- /dev/null
+++ b/start-win10
@@ -0,0 +1,65 @@
+#!/bin/bash
+# requires `cset`
+# available on Fedora through my COPR:
+#  - https://copr.fedorainfracloud.org/coprs/jlay/cpuset/
+# review notes regarding XML entries
+
+# this script:
+# - isolates host tasks from the VM CPUs
+# - applies some generic tweaks
+# - resets host isolation on VM shutdown
+
+# Set the range of cores assigned to the windows VM
+# on an i9-7920x this is the first 8 cores and the corresponding hyperthreads
+VM_CORES='0-7,12-19'
+
+# based on the assignments of pinned CPUs in libvirt XML, eg:
+#    <vcpupin vcpu='0' cpuset='0'/>
+#    <vcpupin vcpu='1' cpuset='12'/>
+#    [...]
+#    <vcpupin vcpu='14' cpuset='7'/>
+#    <vcpupin vcpu='15' cpuset='19'/>
+# 
+# `lscpu -e` and `virsh capabilities` are helpful for determining valid pinning settings
+# on example system (i9 7920x), vCPUs 0-15 are pinned (alternating between) cores 0-7 and hyperthreads 12-19
+
+# reduce kernel jitter
+sudo sysctl vm.stat_interval=120
+sudo sysctl kernel.watchdog=0
+
+# isolate VM CPUs from host tasks
+# VM must have the partition cset uses w/ userset below defined in libvirt XML, eg:
+# 
+#  </cputune> ... reference line
+#  <resource>
+#    <partition>/windows10</partition>
+#  </resource>
+#  <os> ... reference line
+
+# first, attempt to reset shielding.  we want to recreate conflicting names with set params
+sudo cset shield --reset --sysset=host.slice --userset=windows10.slice
+sudo cset set -d windows10.slice
+
+# shield cores
+sudo cset shield -c $VM_CORES --sysset=host.slice --userset=windows10.slice
+
+# start the VM
+sudo virsh start windows10
+
+# set higher priority
+QEMU_PID=$(sudo ps fauxww | awk '$0 ~ /qemu.*windows1[0]/ {print $2}')
+sudo renice -20 -p ${QEMU_PID}
+sudo chrt -f -p 99 ${QEMU_PID}
+
+echo "Waiting for windows10 VM to stop before resetting cpusets"
+while true; do
+	# chill a bit
+	sleep 10
+	# get vm state, check if it's off
+	VM_STATE=$(sudo virsh dominfo windows10 | awk '$1 ~ /State/ {print $NF}')
+	if [ "$VM_STATE" == 'off' ]; then
+		echo -e "windows10 VM shut down, setting cpusets back to normal\n"
+		sudo cset shield --reset --sysset=host.slice --userset=windows10.slice
+		exit 0
+	fi
+done