Detailed method for Linux to dynamically enable and to disable hyperthreading

Preface

intel's hyperthreading technology allows one physical core to execute two threads in parallel, which in most cases improves the utilization of hardware resources and system performance.For cpu-intensive numeric programs, hyperthreading can cause overall program performance degradation.For this reason, it is recommended to turn off hyperthreading when executing OpenMP or MPI numeric programs.

The following is a script that dynamically turns hyperthreading on and off found on github.The principle is based on/sys/devices/system/cpu/cpuX/topology/thread_siblings_The list file finds the relationship between the logical cores and then edits the /sys/devices/system/cpu/cpuX/online file to dynamically open and close the hyperthreading 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

Remarks:

The script requires root privileges to execute; Enabled cpu information can be viewed through cat/proc/cpuinfo, which does not require root privileges; The lscpu command looks at the status of cpu (no root privilege is required): threads per core has a value of 2 in hyperthreaded state and 1 when disabled.

Reference resources

Disable / Enable HyperThreading cores on runtime linux

summary