Linux check whether hyperthreading is enabled or not
There parameters need to be obained: no. of physical CPU; no. of cores on each CPU; no. of all threads.
In my case, the CPU name: Intel(R) Xeon(R) CPU E5-2630 v4 @ 2.20GHz
(1) Check the number of physical CPU
# cat /proc/cpuinfo | grep "physical id" | sort | uniq
physical id : 0
physical id : 1
//// Here we can see the number of physical CPU is 2. Each physical CPU has its own fan.
(2) Check the number of logical cores on each CPU
# cat /proc/cpuinfo | grep "cores" | uniq
cpu cores : 10
//// Here each physical CPU has 10 cores.
(3) Check the number of all threads
# cat /proc/cpuinfo | grep "processor" | wc -l
40
//// After obtaining above three parameters, now we can judge whether the hyperthreading is enabled or not.
In the case withou hyperthreading, number of all threads= no. of physical CPU * no. of cores on each CPU * 1, then there is only one thread on each core.
When hyperthreading is enabled, for example, N threads are available on each core. Then the following relationship can be achived:
number of all threads= no. of physical CPU * no. of cores on each CPU * N.
NOTE: OpenMP
The OpenMP parallel language can also be used to check the number of threads per core.
#include "stdio.h" #include "omp.h" int main() { int num_thread, myid; #pragma omp parallel { num_threads= omp_get_num_threads(); // get the total number of threads on one core myid= omp_get_thread_num(); // get the ID of the current thread printf("\nHello world from the thread %d out of %d threads!"); } return 0; }
Use the following command to compile the C file "hello.c":
$ gcc -fopenmp -o run.o hello.c
$ ./run.o