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authorDietmar Eggemann <dietmar.eggemann@arm.com>2020-09-22 11:39:33 +0300
committerPeter Zijlstra <peterz@infradead.org>2020-10-29 13:00:29 +0300
commit5e054bca44fe92323de5e9b71478d1904b8bb1b7 (patch)
tree0991063aa02b230fb28c37a09078f1cc1ec1de09 /kernel/sched/cpupri.h
parenta57415f5d1e43c3a5c5d412cd85e2792d7ed9b11 (diff)
downloadlinux-5e054bca44fe92323de5e9b71478d1904b8bb1b7.tar.xz
sched/cpupri: Remove pri_to_cpu[CPUPRI_IDLE]
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
Diffstat (limited to 'kernel/sched/cpupri.h')
-rw-r--r--kernel/sched/cpupri.h7
1 files changed, 3 insertions, 4 deletions
diff --git a/kernel/sched/cpupri.h b/kernel/sched/cpupri.h
index efbb492bb94c..1a162369b8d4 100644
--- a/kernel/sched/cpupri.h
+++ b/kernel/sched/cpupri.h
@@ -1,11 +1,10 @@
/* SPDX-License-Identifier: GPL-2.0 */
-#define CPUPRI_NR_PRIORITIES (MAX_RT_PRIO + 2)
+#define CPUPRI_NR_PRIORITIES (MAX_RT_PRIO + 1)
#define CPUPRI_INVALID -1
-#define CPUPRI_IDLE 0
-#define CPUPRI_NORMAL 1
-/* values 2-101 are RT priorities 0-99 */
+#define CPUPRI_NORMAL 0
+/* values 2-100 are RT priorities 0-99 */
struct cpupri_vec {
atomic_t count;