How to bind a process to a set of cpu in golang?

Question

I use os/exec pkg to have a process run. I want to check it cpu affinity and modify it to bind the process to a specific cpu set. I find

func SchedSetaffinity(pid int, set *CPUSet) error

This function is in golang.org/x/sys/unix package . However, it says it just bind a thread to a specific cpu. I don't know wheter it works on process. And I wonder how to get the CPUSet. Is it a value I need to define?

Answer 1

Taskset : To enable a process run on a specific CPU, you use the command 'taskset' in linux. Accordingly you can arrive on a logic based on "taskset -p [mask] [pid]" where the mask represents the cores in which the particular process shall run, provided the whole program runs with GOMAXPROCS=1.

pthread_setaffinity_np : You can use cgo and arrive on a logic that calls pthread_setaffinity_np, as Go uses pthreads in cgo mode. (The pthread_attr_setaffinity_np() function sets the CPU affinity mask attribute of the thread attributes object referred to by attr to the value specified in cpuset. )

Go helps in incorporation of affinity control via "SchedSetaffinity" that can be checked for confining a thread to specific cores. Accordingly , you can arrive on a logic for usage of "SchedSetaffinity(pid int, set *CPUSet)" that sets the CPU affinity mask of the thread specified by pid. If pid is 0 the calling thread is used.

It should be noted that GOMAXPROCS variable limits the number of operating system threads that can execute user-level Go code simultaneously. If it is > 1 then, you may use runtime.LockOSThread of Go that shall pin the current goroutine to the current thread that is is running on . The calling goroutine will always execute in that thread, and no other goroutine will execute in it, until the calling goroutine has made as many calls to UnlockOSThread as to LockOSThread.

cgroups : There is also option of using cgroups that helps in organizing the processes hierarchically and distribution of system resources along the hierarchy in a controlled and configurable manner. Here, there is subsystem termed as cpuset that enables assigning individual CPUs (on a multicore system) and memory nodes to process in a cgroup. The cpuset lists CPUs to be used by tasks within this cgroup. The CPU numbers are comma-separated numbers or ranges. For example:

#cat cpuset.cpus
0-4,6,8-10

A process is confined to run only on the CPUs in the cpuset it belongs to, and to allocate memory only on the memory nodes in that cpuset. It should be noted that all processes are put in the cgroup that the parent process belongs to at the time on creation and a process can be migrated to another cgroup. Migration of a process doesn't affect already existing descendant processes.