调度程序是否可以通过`sched_setaffinity`自动将亲和性已设置为非常繁忙的cpu的线程迁移到空闲cpu？

Question

Could scheduler automatically migrate the thread whose affinity has been set to a very busy cpu through sched_setaffinity to a free cpu?

Does sched_setaffinity implement a "hard affinity" or a "soft affinity"?

What i called "soft affinity" is that it tells scheduler the thread prefers to run on a particular cpu and could be migrated to other cpu if necessary.

What i called "hard affinity" is that it tells scheduler the thread must run on particular cpu no matter how long the thread has to wait for the cpu resources.

I clearly remember that there are apis which could provide "soft affinity" and "hard affinity" under windows indeed.Is there any api could provide "soft affinity" under linux?

Answer 1

No. If a process has affinity to one CPU only, it will only run on that CPU no matter what. In other words, this fits your definition of "hard affinity".

This feature can of course be a double edged sword if used incorrectly: setting the affinity of a task to a single CPU gives great benefit if the CPU is dedicated to that task only, but degrades performance if the CPU is not and it somehow gets under heavy load.