Detailed explanation of how to dynamically enable/disable hyperthreading technology in Linux

Preface

Intel's hyper-threading technology allows two threads to be executed in parallel on one physical core, which in most cases can improve the utilization of hardware resources and enhance system performance. For CPU-intensive numerical programs, hyperthreading technology may cause overall program performance to degrade. For this reason, it is recommended to disable hyperthreading technology when executing OpenMP or MPI numerical programs.

The following is a script found on github that dynamically turns on and off hyper-threading technology. The principle is to find the relationship between logical cores according to the /sys/devices/system/cpu/cpuX/topology/thread_siblings_list file, and then edit the /sys/devices/system/cpu/cpuX/online file to dynamically turn on and off hyper-threading technology.

#!/bin/bash

HYPERTHREADING=1

function toggleHyperThreading() {
 for CPU in /sys/devices/system/cpu/cpu[0-9]*; do
   CPUID=`basename $CPU | cut -b4-`
   echo -en "CPU: $CPUID\t"
   [ -e $CPU/online ] && echo "1" > $CPU/online
   THREAD1=`cat $CPU/topology/thread_siblings_list | cut -f1 -d,`
   if [ $CPUID = $THREAD1 ]; then
     echo "-> enable"
     [ -e $CPU/online ] && echo "1" > $CPU/online
   else
    if [ "$HYPERTHREADING" -eq "0" ]; then echo "-> disabled"; else echo "-> enabled"; fi
     echo "$HYPERTHREADING" > $CPU/online
   fi
 done
}

function enabled() {
    echo -en "Enabling HyperThreading\n"
    HYPERTHREADING=1
    toggleHyperThreading
}

function disabled() {
    echo -en "Disabling HyperThreading\n"
    HYPERTHREADING=0
    toggleHyperThreading
}

#
ONLINE=$(cat /sys/devices/system/cpu/online)
OFFLINE=$(cat /sys/devices/system/cpu/offline)
echo "---------------------------------------------------"
echo -en "CPU's online: $ONLINE\t CPU's offline: $OFFLINE\n"
echo "---------------------------------------------------"
while true; do
  read -p "Type in e to enable or d disable hyperThreading or q to quit [e/d/q] ?" ed
  case $ed in
    [Ee]* ) enabled; break;;
    [Dd]* ) disabled;exit;;
    [Qq]* ) exit;;
    * ) echo "Please answer e for enable or d for disable hyperThreading.";;
  esac
done

Remark:

1. The script needs root privileges to execute;
2. You can view the enabled CPU information through cat /proc/cpuinfo. This command does not require root privileges.
3. The lscpu command can be used to view the status of the CPU (no root privileges are required): the threads per core value is 2 when hyperthreading is enabled and 1 when disabled.

refer to

Disable / Enable HyperThreading cores on runtime – linux

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