Messages in this thread | | | Date | Wed, 10 Apr 2024 19:24:23 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH V6 1/6] sched/fair: Add trivial fair server |
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On Fri, Apr 05, 2024 at 07:28:00PM +0200, Daniel Bristot de Oliveira wrote: > From: Peter Zijlstra <peterz@infradead.org> > > Use deadline servers to service fair tasks. > > This patch adds a fair_server deadline entity which acts as a container > for fair entities and can be used to fix starvation when higher priority > (wrt fair) tasks are monopolizing CPU(s). > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org> > --- > kernel/sched/core.c | 24 ++++++++++++++++-------- > kernel/sched/deadline.c | 23 +++++++++++++++++++++++ > kernel/sched/fair.c | 25 +++++++++++++++++++++++++ > kernel/sched/sched.h | 4 ++++ > 4 files changed, 68 insertions(+), 8 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 7019a40457a6..04e2270487b7 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -6007,6 +6007,14 @@ static void put_prev_task_balance(struct rq *rq, struct task_struct *prev, > #endif > > put_prev_task(rq, prev); > + > + /* > + * We've updated @prev and no longer need the server link, clear it. > + * Must be done before ->pick_next_task() because that can (re)set > + * ->dl_server. > + */ > + if (prev->dl_server) > + prev->dl_server = NULL; > } > > /* > @@ -6037,6 +6045,13 @@ __pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) > p = pick_next_task_idle(rq); > } > > + /* > + * This is a normal CFS pick, but the previous could be a DL pick. > + * Clear it as previous is no longer picked. > + */ > + if (prev->dl_server) > + prev->dl_server = NULL; > + > /* > * This is the fast path; it cannot be a DL server pick; > * therefore even if @p == @prev, ->dl_server must be NULL. > @@ -6050,14 +6065,6 @@ __pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) > restart: > put_prev_task_balance(rq, prev, rf); > > - /* > - * We've updated @prev and no longer need the server link, clear it. > - * Must be done before ->pick_next_task() because that can (re)set > - * ->dl_server. > - */ > - if (prev->dl_server) > - prev->dl_server = NULL; > - > for_each_class(class) { > p = class->pick_next_task(rq); > if (p)
This bit seems like a fix for 63ba8422f876 ("sched/deadline: Introduce deadline servers"), should it be a separate patch?
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