Messages in this thread | | | From | John Stultz <> | Date | Mon, 8 Apr 2024 12:51:22 -0700 | Subject | Re: [PATCH] sched/pi: Reweight fair_policy() tasks when inheriting prio |
| |
On Mon, Apr 8, 2024 at 12:17 AM Vincent Guittot <vincent.guittot@linaro.org> wrote: > > On Sun, 7 Apr 2024 at 14:27, Qais Yousef <qyousef@layalina.io> wrote: > > > > On 04/05/24 18:16, Qais Yousef wrote: > > > > > > > > > > All that to say that I think the weight is not applied on purpose. > > > > This might work for your particular case but there are more changes to > > > > be done if you want to apply prio inheritance between cfs tasks. > > > > > > > > As an example, what about the impact of cgroup on the actual weight > > > > and the inherited priority of a task ? If the owner and the waiter > > > > don't belong to the same cgroup their own prio is meaningless... task > > > > nice -20 in a group with a weight equal to nice 19 vs a task nice 19 > > > > in a group with a weight equals to nice -20 > > > > > > That is on my mind actually. But I thought it's a separate problem. That has to > > > do with how we calculate the effective priority of the pi_task. And probably > > > the sorting order to if we agree we need to revert the above. If that is done > > > > Thinking more about it the revert is not the right thing to do. We want fair > > tasks to stay ordered in FIFO for better fairness and avoid potential > > starvation issues. It's just the logic for searching the top_waiter need to be > > different. If the top_waiter is fair, then we need to traverse the tree to find > > the highest nice value. We probably can keep track of this while adding items > > to the tree to avoid the search. > > > > For cgroup; is it reasonable (loosely speaking) to keep track of pi_cfs_rq and > > detach_attach_task_cfs_rq() before the reweight? This seems the most > > straightforward solution and will contain the complexity to keeping track of > > cfs_rq. But it'll have similar issue to proxy execution where a task that > > doesn't belong to the cgroup will consume its share.. > > That's a good point, Would proxy execution be the simplest way to fix all this ?
So, at the moment, in part. It ought to resolve the issue for in-kernel mutexes (blocked tasks stay on rq, if blocked tasks are selected to run we will instead run the runnable lock owner - thus it works across scheduling classes), but it isn't tied into userland futexes the way rt_mutexes are at this point.
Review and feedback on the series would be greatly appreciated! (Nudge! Nudge! :) -john
| |