Merge pull request 'update comments, require less sudo' (#1) from update-win10-script into master

Reviewed-on: https://git.jlay.dev/jlay/vfio/pulls/1

start-win10

@@ -1,50 +1,64 @@
 #!/bin/bash
-# requires `cset`
+#
+# script to create cpusets to isolate CPU threads for KVM/libvirt VMs
+# requires 'cset'
 # available on Fedora through my COPR:
 #  - https://copr.fedorainfracloud.org/coprs/jlay/cpuset/
-# review notes regarding XML entries
-
+# review comments below regarding CPUs and 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:
+#
+# define the CPUs (cores/threads) to isolate for the VM
+VM_CORES='0-11,24-35'
+# Tip: refer to 'virsh capabilities | grep siblings'
+# this will show CPU topology information for the host
+# allows one to pick optimal layout for the VM
+#
+# the pinned CPUs are definend like so in the VM libvirt XML:
 #    <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
-
+#    <vcpupin vcpu='1' cpuset='24'/>
+#    <vcpupin vcpu='2' cpuset='1'/>
+#    <vcpupin vcpu='3' cpuset='25'/>
+# [...]
+#     <emulatorpin cpuset='10-11'/>
+#
+# NOTE: the pinned emulator CPUs must be included in VM_CORES
+# probably any iothreads too
+#
+# example above is based on a threadripper 3960x:
+#  - one NUMA node
+#  - SMT enabled
+#
 # 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
+# attempt to reset shielding, we want to create it with current params
+# and remove any existing slices from previous VM boots
+# we want it to be created with current params, such as possibly-changed pinned CPUs
 sudo cset shield --reset --sysset=host.slice --userset=windows10.slice
 sudo cset set -d windows10.slice
 
 # shield cores
+# userset slice must match the partition defined in libvirt xml, eg:
+#
+#  </cputune>
+#  <resource>
+#    <partition>/windows10</partition>
+#  </resource>
+#  <os>
 sudo cset shield -c $VM_CORES --sysset=host.slice --userset=windows10.slice
 
+# setup looking glass
+#sudo touch /dev/shm/looking-glass
+#sudo chown jlay:kvm /dev/shm/looking-glass
+#sudo chmod 660 /dev/shm/looking-glass
+
 # start the VM
-sudo virsh start windows10
+virsh start windows10
 
 # set higher priority
 QEMU_PID=$(sudo ps fauxww | awk '$0 ~ /qemu.*windows1[0]/ {print $2}')