Re: [External] Re: [PATCH] cgroup/cpuset: Add a new isolated mems.policy type.

[Zhongkun He]

> > > Back to the previous question.
> > > > The question is how to implement that with a sensible semantic.
> > >
> > > Thanks for your analysis and suggestions.It is really difficult to add
> > > policy directly to cgroup for the hierarchical enforcement. It would 
> > > be a good idea to add pidfd_set_mempolicy.
> >
> > Are you going to pursue that path?

> Hi Michal, thanks for your suggestion and reply.
>
>  > Are you going to pursue that path?
>
> Yes，I'll give it a try as it makes sense to modify the policy dynamically.
>
> Thanks.

Hi Michal, i have a question about pidfd_set_mempolicy, it would be 
better if you have some suggestions.

The task_struct of processes and threads are independent. If we change 
the mempolicy of the process through pidfd_set_mempolicy, the mempolicy 
of its thread will not change. Of course users can set the mempolicy of 
all threads by iterating through /proc/tgid/task.

The question is whether we should override the thread's mempolicy when 
setting the process's mempolicy.

There are two options:
A:Change the process's mempolicy and set that mempolicy to all it's threads.
B:Only change the process's mempolicy in kernel. The mempolicy of the 
thread needs to be modified by the user through pidfd_set_mempolicy in
userspace, if necessary.

Thanks.