Fix ~42 single-word typos in scheduler code comments. We have accumulated a few fun ones over the years. :-) Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Vincent Guittot <vincent.guittot@linaro.org> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Ben Segall <bsegall@google.com> Cc: Mel Gorman <mgorman@suse.de> Cc: linux-kernel@vger.kernel.org
We want migrate_disable() tasks to get PULLs in order for them to PUSH away the higher priority task. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com> Link: https://lkml.kernel.org/r/20201023102347.310519774@infradead.org
Add CPUPRI_HIGHER above the RT99 priority to denote the CPU is in use by higher priority tasks (specifically deadline). XXX: we should probably drive PUSH-PULL from cpupri, that would automagically result in an RT-PUSH when DL sets cpupri to CPUPRI_HIGHER. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
This makes the mapping continuous and frees up 100 for other usage.
Prev mapping:
p->rt_priority p->prio newpri cpupri
-1 -1 (CPUPRI_INVALID)
100 0 (CPUPRI_NORMAL)
1 98 98 1
...
49 50 50 49
50 49 49 50
...
99 0 0 99
New mapping:
p->rt_priority p->prio newpri cpupri
-1 -1 (CPUPRI_INVALID)
99 0 (CPUPRI_NORMAL)
1 98 98 1
...
49 50 50 49
50 49 49 50
...
99 0 0 99
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
pri_to_cpu[1] isn't used since cpupri_set(..., newpri) is
never called with newpri = 99.
The valid RT priorities RT1..RT99 (p->rt_priority = [1..99]) map into
cpupri (idx of pri_to_cpu[]) = [2..100]
Current mapping:
p->rt_priority p->prio newpri cpupri
-1 -1 (CPUPRI_INVALID)
100 0 (CPUPRI_NORMAL)
1 98 98 2
...
49 50 50 50
50 49 49 51
...
99 0 0 100
So cpupri = 1 isn't used.
Reduce the size of pri_to_cpu[] by 1 and adapt the cpupri
implementation accordingly. This will save a useless for loop with an
atomic_read in cpupri_find_fitness() calling __cpupri_find().
New mapping:
p->rt_priority p->prio newpri cpupri
-1 -1 (CPUPRI_INVALID)
100 0 (CPUPRI_NORMAL)
1 98 98 1
...
49 50 50 49
50 49 49 50
...
99 0 0 99
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200922083934.19275-3-dietmar.eggemann@arm.com
pri_to_cpu[CPUPRI_IDLE=0] isn't used since cpupri_set(..., newpri) is
never called with newpri = MAX_PRIO (140).
Current mapping:
p->rt_priority p->prio newpri cpupri
-1 -1 (CPUPRI_INVALID)
140 0 (CPUPRI_IDLE)
100 1 (CPUPRI_NORMAL)
1 98 98 3
...
49 50 50 51
50 49 49 52
...
99 0 0 101
Even when cpupri was introduced with commit 6e0534f27819 ("sched: use a
2-d bitmap for searching lowest-pri CPU") in v2.6.27, only
(1) CPUPRI_INVALID (-1),
(2) MAX_RT_PRIO (100),
(3) an RT prio (RT1..RT99)
were used as newprio in cpupri_set(..., newpri) -> convert_prio(newpri).
MAX_RT_PRIO is used only in dec_rt_tasks() -> dec_rt_prio() ->
dec_rt_prio_smp() -> cpupri_set() in case of !rt_rq->rt_nr_running.
I.e. it stands for a non-rt task, including the IDLE task.
Commit 57785df5ac53 ("sched: Fix task priority bug") removed code in
v2.6.33 which did set the priority of the IDLE task to MAX_PRIO.
Although this happened after the introduction of cpupri, it didn't have
an effect on the values used for cpupri_set(..., newpri).
Remove CPUPRI_IDLE and adapt the cpupri implementation accordingly.
This will save a useless for loop with an atomic_read in
cpupri_find_fitness() calling __cpupri_find().
New mapping:
p->rt_priority p->prio newpri cpupri
-1 -1 (CPUPRI_INVALID)
100 0 (CPUPRI_NORMAL)
1 98 98 2
...
49 50 50 50
50 49 49 51
...
99 0 0 100
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200922083934.19275-2-dietmar.eggemann@arm.com
If we failed to find a fitting CPU, in cpupri_find(), we only fallback to the level we found a hit at. But Steve suggested to fallback to a second full scan instead as this could be a better effort. https://lore.kernel.org/lkml/20200304135404.146c56eb@gandalf.local.home/ We trigger the 2nd search unconditionally since the argument about triggering a full search is that the recorded fall back level might have become empty by then. Which means storing any data about what happened would be meaningless and stale. I had a humble try at timing it and it seemed okay for the small 6 CPUs system I was running on https://lore.kernel.org/lkml/20200305124324.42x6ehjxbnjkklnh@e107158-lin.cambridge.arm.com/ On large system this second full scan could be expensive. But there are no users outside capacity awareness for this fitness function at the moment. Heterogeneous systems tend to be small with 8cores in total. Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Link: https://lkml.kernel.org/r/20200310142219.syxzn5ljpdxqtbgx@e107158-lin.cambridge.arm.com
By introducing a new cpupri_find_fitness() function that takes the
fitness_fn as an argument and only called when asym_system static key is
enabled.
cpupri_find() is now a wrapper function that calls cpupri_find_fitness()
passing NULL as a fitness_fn, hence disabling the logic that handles
fitness by default.
LINK: https://lore.kernel.org/lkml/c0772fca-0a4b-c88d-fdf2-5715fcf8447b@arm.com/
Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: 804d402fb6f6 ("sched/rt: Make RT capacity-aware")
Link: https://lkml.kernel.org/r/20200302132721.8353-4-qais.yousef@arm.com
When searching for the best lowest_mask with a fitness_fn passed, make
sure we record the lowest_level that returns a valid lowest_mask so that
we can use that as a fallback in case we fail to find a fitting CPU at
all levels.
The intention in the original patch was not to allow a down migration to
unfitting CPU. But this missed the case where we are already running on
unfitting one.
With this change now RT tasks can still move between unfitting CPUs when
they're already running on such CPU.
And as Steve suggested; to adhere to the strict priority rules of RT, if
a task is already running on a fitting CPU but due to priority it can't
run on it, allow it to downmigrate to unfitting CPU so it can run.
Reported-by: Pavan Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: 804d402fb6f6 ("sched/rt: Make RT capacity-aware")
Link: https://lkml.kernel.org/r/20200302132721.8353-2-qais.yousef@arm.com
Link: https://lore.kernel.org/lkml/20200203142712.a7yvlyo2y3le5cpn@e107158-lin/