From: "tip-bot2 for Dietmar Eggemann" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
x86 <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: [tip: sched/core] sched/cpupri: Remove pri_to_cpu[1]
Date: Thu, 29 Oct 2020 10:51:49 -0000 [thread overview]
Message-ID: <160396870990.397.13763662113721048647.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20200922083934.19275-3-dietmar.eggemann@arm.com>
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 1b08782ce31f612d98e11ccccf3e3df9a147a67d
Gitweb: https://git.kernel.org/tip/1b08782ce31f612d98e11ccccf3e3df9a147a67d
Author: Dietmar Eggemann <dietmar.eggemann@arm.com>
AuthorDate: Tue, 22 Sep 2020 10:39:34 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Thu, 29 Oct 2020 11:00:29 +01:00
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
---
kernel/sched/cpupri.c | 6 +++---
kernel/sched/cpupri.h | 4 ++--
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/cpupri.c b/kernel/sched/cpupri.c
index a5d14ed..8d9952a 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;
}
diff --git a/kernel/sched/cpupri.h b/kernel/sched/cpupri.h
index 1a16236..e28e1ed 100644
--- a/kernel/sched/cpupri.h
+++ b/kernel/sched/cpupri.h
@@ -1,10 +1,10 @@
/* SPDX-License-Identifier: GPL-2.0 */
-#define CPUPRI_NR_PRIORITIES (MAX_RT_PRIO + 1)
+#define CPUPRI_NR_PRIORITIES MAX_RT_PRIO
#define CPUPRI_INVALID -1
#define CPUPRI_NORMAL 0
-/* values 2-100 are RT priorities 0-99 */
+/* values 1-99 are for RT1-RT99 priorities */
struct cpupri_vec {
atomic_t count;
next prev parent reply other threads:[~2020-10-29 10:52 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 8:39 [PATCH 0/2] sched/cpupri: Cleanup cpu priority vector handling Dietmar Eggemann
2020-09-22 8:39 ` [PATCH 1/2] sched/cpupri: Remove pri_to_cpu[CPUPRI_IDLE] Dietmar Eggemann
2020-10-29 10:51 ` [tip: sched/core] " tip-bot2 for Dietmar Eggemann
2020-09-22 8:39 ` [PATCH 2/2] sched/cpupri: Remove pri_to_cpu[1] Dietmar Eggemann
2020-10-29 10:51 ` tip-bot2 for Dietmar Eggemann [this message]
2020-10-14 19:46 ` [PATCH 0/2] sched/cpupri: Cleanup cpu priority vector handling Peter Zijlstra
2020-10-14 19:48 ` [PATCH 3/2] sched/cpupri: Remap CPUPRI_NORMAL to MAX_RT_PRIO-1 Peter Zijlstra
2020-10-19 14:14 ` Dietmar Eggemann
2020-10-20 7:22 ` Peter Zijlstra
2020-10-14 19:54 ` [PATCH 4/2] sched/cpupri: Add CPUPRI_HIGHER Peter Zijlstra
2020-10-19 14:15 ` Dietmar Eggemann
2020-10-20 7:37 ` Peter Zijlstra
2020-10-20 15:39 ` Dietmar Eggemann
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