#!/bin/bash

# 2024.feb kneutron
# mod for lxc

# optional arg1 $1 = vmid if already known
# Assign cores 2-7 to 6-core lxc on 8-core host
#   OR Assign cores 7-5 to 3-core vm on 8-core host

# Features:
# Auto-determines last core number
# Adapts on-the-fly to 2,3+ vcpus (up to 6) 
#   Can be extended easily for more vcpu counts
# This should obviously be done on quad-core or better CPU

# script in PATH
psax

declare -i vmid lastcpu penultcpu  # has to be a number

if [ "$1" = "" ]; then
  read -p "Enter ID of highest-CPU LXC: " lxcid
else
  lxcid=$1
fi

[ "$lxcid" = "" ] || [ "$lxcid" = "0" ] && exit 44;

lastcpu=$(grep processor /proc/cpuinfo |tail -n 1 |awk '{print $3}')
let penultcpu=$lastcpu-1

# SKIP print only pid / subthreads that are using >0 CPU
# /usr/bin/lxc-start -F -n 105
pidlist=$(ps -eLf --columns $COLUMNS |grep "lxc-start .*$lxcid" |egrep -v 'grep|bash' |awk '{print $4}')
echo $pidlist

#exit; 

function assigncores () {
 
set -x
 taskset -p $1
 taskset -cp $penultcpu,$lastcpu $1
 
 taskset -cp $lastcpu $2
 taskset -cp $penultcpu $3
 
 let penultcpu=$penultcpu-1
[ "$4" = "" ] || taskset -cp $penultcpu $4
 let penultcpu=$penultcpu-1
[ "$5" = "" ] || taskset -cp $penultcpu $5
 let penultcpu=$penultcpu-1
[ "$6" = "" ] || taskset -cp $penultcpu $6
 let penultcpu=$penultcpu-1
[ "$7" = "" ] || taskset -cp $penultcpu $7
}
# assign cpu cores 6,7 to win10 vm for better latency
# REF: https://www.youtube.com/watch?v=-c_451HV6fE

# psthreads.sh 'kvm -id 112' |awk '$5>0 {print}' # field 4 is pid + subthreads

assigncores $pidlist

set +x
echo "Monitor changes with htop"

exit;

Alt.method:

ps ax |grep "kvm -id 112"

# show threads with cpu
ps -T -p 12690 |grep CPU
  12690   12781 ?        23:02:08 CPU 0/KVM
  12690   12782 ?        21:17:16 CPU 1/KVM
  12690   12783 ?        1-02:24:12 CPU 2/KVM

# Adapt to different multicore systems

# grep processor /proc/cpuinfo |tail -n 1
processor       : 7
# grep processor /proc/cpuinfo |tail -n 1 |awk '{print $3}'
7