Optimize syscall.c: Change getpid method to syscall

Optimize syscall.c: Change getpid method to syscall

optimize whets

Optimize whets.c:
When the main frequency of the CPU is higher, the time of N8 process is nonlinear.
More infomation, you can see: https://yq.aliyun.com/articles/674732

v5.1.4

v5.1.4
Optimize contetxt1.c:
Sometimes parent and child process will run on the same CPU, now we make parent process and child process run on different CPUs.