Linux动态启用/禁用超线程技术

intel的超线程技术能让一个物理核上并行执行两个线程，大多数情况下能提高硬件资源的利用率，增强系统性能。对于cpu密集型的数值程序，超线程技术可能会导致整体程序性能下降。鉴于此，执行OpenMP或者MPI数值程序时建议关闭超线程技术。

以下是github上找到的动态打开、关闭超线程技术的脚本。其原理是根据/sys/devices/system/cpu/cpuX/topology/thread_siblings_list文件找到逻辑核的关系，然后编辑/sys/devices/system/cpu/cpuX/online文件实现动态开启和关闭超线程技术。

#!/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

备注：

1. 脚本需root权限执行；
2. 可以通过cat /proc/cpuinfo查看启用的cpu信息，该命令无需root权限；
3. lscpu命令可查看cpu的状态（无需root权限）：超线程状态下threads per core数值为2，禁用时为1.

参考

1. Disable / Enable HyperThreading cores on runtime – linux