On Thu, Apr 07, 2016 at 03:35:47AM -0400, Johannes Weiner wrote:

There was a lot of back and forth whether we should add a second set
of knobs just to control the local tasks separately from the subtree,
but ended up concluding that the situation can be expressed more
clearly by creating dedicated leaf subgroups for stuff like management
software and launchers instead, so that their memory pools/LRUs are
clearly delineated from other groups and seperately controllable. And
we couldn't think of any meaningful configuration that could not be
expressed in that scheme. I mean, it's the same thing, right?

No, not the same.


	R
      / | \
     t1	t2 A
         /   \
        t3   t4


Is fundamentally different from:


             R
	   /   \
	 L       A
       /   \   /   \
      t1  t2  t3   t4


Because if in the first hierarchy you add a task (t5) to R, all of its A
will run at 1/4th of total bandwidth where before it had 1/3rd, whereas
with the second example, if you add our t5 to L, A doesn't get any less
bandwidth.


Please pull your collective heads out of the systemd arse and start
thinking.