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

[Zhongkun He]

> On Wed 07-09-22 21:50:24, Zhongkun He wrote:
> [...]
> > > Do you really need to change the policy itself or only the effective
> > > nodemask? Do you need any other policy than bind and preferred?
> >
> > Yes, we need to change the policy, not only his nodemask. we really want
> > policy is interleave, and extend it to weight-interleave.
> > Say something like the following
> > 			node       weight
> >      interleave:		 0-3       1:1:1:1  default one by one
> >      weight-interleave:   0-3       1:2:4:6  alloc pages by weight
> > 					    (User set weight.)
> > In the actual usecase, the remaining resources of each node are different,
> > and the use of interleave cannot maximize the use of resources.
>
> OK, this seems a separate topic. It would be good to start by proposing
> that new policy in isolation with the semantic description.
>
> > 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?
>   
> > Also, there is a new idea.
> > We can try to separate the elements of mempolicy and use them independently.
> > Mempolicy has two meanings:
> >      nodes:which nodes to use(nodes,0-3), we can use cpuset's effective_mems
> > directly.
> >      mode:how to use them(bind,prefer,etc). change the mode to a
> > cpuset->flags,such as CS_INTERLEAVE。
> > task_struct->mems_allowed is equal to cpuset->effective_mems,which is
> > hierarchical enforcement。CS_INTERLEAVE can also be updated into tasks，
> > just like other flags(CS_SPREAD_PAGE).
> > When a process needs to allocate memory, it can find the appropriate node to
> > allocate pages according to the flag and mems_allowed.
>
> I am not sure I see the advantage as the mode and nodes are always
> closely coupled. You cannot really have one wihtout the other.

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.