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| author | Dietmar Eggemann <dietmar.eggemann@arm.com> | 2020-09-22 10:39:34 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-10-29 11:00:29 +0100 |
| commit | 1b08782ce31f612d98e11ccccf3e3df9a147a67d (patch) | |
| tree | 99eee9c6748240acdc77f19085265916d3c89ab1 /kernel/sched/cpupri.c | |
| parent | 5e054bca44fe92323de5e9b71478d1904b8bb1b7 (diff) | |
| download | linux-1b08782ce31f612d98e11ccccf3e3df9a147a67d.tar.bz2 | |
sched/cpupri: Remove pri_to_cpu[1]
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
Diffstat (limited to 'kernel/sched/cpupri.c')
| -rw-r--r-- | kernel/sched/cpupri.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/sched/cpupri.c b/kernel/sched/cpupri.c index a5d14ed485f4..8d9952a51664 100644 --- a/kernel/sched/cpupri.c +++ b/kernel/sched/cpupri.c @@ -19,12 +19,12 @@ * in that class). Therefore a typical application without affinity * restrictions can find a suitable CPU with O(1) complexity (e.g. two bit * searches). For tasks with affinity restrictions, the algorithm has a - * worst case complexity of O(min(101, nr_domcpus)), though the scenario that + * worst case complexity of O(min(100, nr_domcpus)), though the scenario that * yields the worst case search is fairly contrived. */ #include "sched.h" -/* Convert between a 140 based task->prio, and our 101 based cpupri */ +/* Convert between a 140 based task->prio, and our 100 based cpupri */ static int convert_prio(int prio) { int cpupri; @@ -34,7 +34,7 @@ static int convert_prio(int prio) else if (prio >= MAX_RT_PRIO) cpupri = CPUPRI_NORMAL; else - cpupri = MAX_RT_PRIO - prio; + cpupri = MAX_RT_PRIO - prio - 1; return cpupri; } |