[dm-devel] Re: dm-ioband: Test results.

[Ryo Tsuruta]

Hi Vivek,

> > I could see the priority inversion by running Vivek's script and I
> > understand how RT requests has to be handled. I'll create a patch
> > which makes dm-ioband cooperates with CFQ scheduler. However, do you
> > think we need some kind of limitation on processes which belong to the
> > RT class to prevent the processes from depleting bandwidth?
>
> I think to begin with, we can keep the same behavior as CFQ. An RT task
> can starve other tasks.
> 
> But we should provide two configurations and user can choose any one.
> If RT task is in root group, it will starve other sibling tasks/groups. If
> it is with-in a cgroup, then it will starve its sibling only with-in that
> cgroup and will not impact other cgroups.
> 
> What I mean is following.
> 
> 			root
> 			/  \
> 		      RT   group1
> 
> In above configuration RT task will starve everybody else.
> 
> 			root
> 		        /   \
> 		   group1   group2
> 		   /  \
> 	         RT   BE
> 
> In above configuration  RT task will starve only sibling in group1 but
> will not starve the tasks in group2 or in root.

Thanks for the suggestion. I'll try this way when dm-ioband supports
hierarchical grouping.

Thanks,
Ryo Tsuruta