On Wednesday, December 20, 2017 2:28:26 PM CET Peter Zijlstra wrote: > On Wed, Dec 20, 2017 at 12:55:46PM +0000, Patrick Bellasi wrote: > > On 20-Dec 09:31, Peter Zijlstra wrote: > > > > Didn't juri have patches to make DL do something sane? But yes, I think > > > those flags are part of the problem. > > > > He recently reposted them here: > > > > https://lkml.kernel.org/r/20171204102325.5110-1-juri.le...@redhat.com > > Yeah, just found them and actually munged them into my queue; did all > the modifications you suggested too. Lets see if it comes apart.
Good, because I think that the Juri's patches should go in first. Then we'll see what's still missing. > > > > - From the utilization handler, we check runqueues of all three sched > > > > classes to see if they have some work pending (this can be done > > > > smartly by checking only RT first and skipping other checks if RT > > > > has some work). > > > > > > No that's wrong. DL should provide a minimum required based on existing > > > reservations, we can add the expected CFS average on top and request > > > that. > > > > > > And for RT all we need to know is if current is of that class, otherwise > > > we don't care. > > > > So, this: > > > > https://marc.info/?i=20171130114723.29210-3-patrick.bellasi%40arm.com > > Right, I was actually looking for those patches, but I'm searching > backwards and hit upon Juri's patches first. > > > was actually going in this direction, although still working on top of > > flags to not change the existing interface too much. > > > > IMO, the advantage of flags is that they are a sort-of "pro-active" > > approach, where the scheduler notify sensible events to schedutil. > > But keep adding flags seems to overkilling to me too. > > > > If we remove flags then we have to query the scheduler classes "on > > demand"... but, as Peter suggests, once we have DL bits Juri posted, > > the only issue if to know if an RT task is running. > > This the patch above can be just good enough, with no flags at all and > > with just a check for current being RT (or DL for the time being). > > Well, we still need flags for crap like IO-WAIT IIRC. That's sugov > internal state and not something the scheduler actually already knows. Not only sugov to be precise, but yes. Thanks, Rafael
