On Tue, Mar 1, 2016 at 4:04 PM, Peter Zijlstra [off-list ref] wrote:

On Tue, Mar 01, 2016 at 02:42:10PM +0000, Juri Lelli wrote:

quoted

Agree. My point was actually more about Rafael's schedutil RFC (I should
probably have posted this there, but I thought it fitted well with this
example). I realize that Rafael is starting simple, but I fear that some
aggregation of util coming from the different classes will be needed in
the end; schedfreq has already something along this line.

Right, but I'm not sure that's a hard thing to add. But yes, it needs
doing.

It also very much has a bearing on the OPP state selection. As already
pointed out, the nearest OPP thing Rafael did is just wrong for DL.

It probably makes sense to pass a CPPC like form into the (software) OPP
selector.

quoted

IMHO, the general approach would be that every scheduling class has an
interface to communicate its util requirement. Then RT will probably
have to ask for max, but CFS and DL will do better.

Right, so on IRC you mentioned that we could also use the global (or
cgroup) RT throttle to lower the RT util/OPP.

The current code simply treats RT/DL as "uknknown" and will always ask
for the max for them.  That should work, although it's suboptimal for
DL at least.  However, I'd prefer to add something more sophisticated
on top of it just to keep things simple to start with.