On 08/05/19 10:14, luca abeni wrote: > Hi Juri, > > On Wed, 8 May 2019 10:01:16 +0200 > Juri Lelli <juri.le...@redhat.com> wrote: > > > Hi Luca, > > > > On 06/05/19 06:48, Luca Abeni wrote: > > > From: luca abeni <luca.ab...@santannapisa.it> > > > > > > Currently, the scheduler tries to find a proper placement for > > > SCHED_DEADLINE tasks when they are pushed out of a core or when > > > they wake up. Hence, if there is a single SCHED_DEADLINE task > > > that never blocks and wakes up, such a task is never migrated to > > > an appropriate CPU core, but continues to execute on its original > > > core. > > > > > > This commit addresses the issue by trying to migrate a > > > SCHED_DEADLINE task (searching for an appropriate CPU core) the > > > first time it is throttled. > > > > Why we failed to put the task on a CPU with enough (max) capacity > > right after it passed admission control? The very first time the task > > was scheduled I mean. > > I think the currently executing task cannot be pushed out of a > CPU/core, right? > > So, if a task switches from SCHED_OTHER to SCHED_DEADLINE while it is > executing on a fast core, the only way to migrate it would be to > preempt it (by using the stop_sched_class, I think), no? > (the typical situation here is a "cpu hog" task that switches from > SCHED_OTHER to SCHED_DEADLINE, and it is the only SCHED_DEADLINE > task... The task never blocks, so push/pull functions are never invoked) > > Or am I missing something?
OK, but "ideally" we should not be waiting to it to be throttled, right? I wonder if you could queue a balance callback in switched_to_dl() (from check_class_changed()), so that it is picked up by balance_callback() before setscheduler returns.
