Improve ruby's performance by locking to a single CPU

ruby-taskset.sh

#!/bin/bash

# Ruby's GIL is a liability when actually doing CPU work
# on a large SMP machine, doubly so on NUMA. This works around it.

# Ruby processes are locked onto a single core + its HT sibling
# on intel machines, 2 cores on AMD. Ideally this would lock to
# one core on non-HT processors, but all of mine are HT so it WFM.

max_cpu=$(cat /proc/cpuinfo |awk -F ': ' '/processor/{print $2}' |tail -n 1)

i=0
for proc in $(ps -o pid= -C ruby)
do
  taskset -cp $i,$(($i+1)) $proc
  
  let i='i+2'
  if [ $i -gt $max_cpu ] ; then
    i=0
  fi
done