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sched/cpupri: Remap CPUPRI_NORMAL to MAX_RT_PRIO-1

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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>
This commit is contained in:
Peter Zijlstra
2020-10-14 21:06:49 +02:00
parent 1b08782ce3
commit 934fc3314b
2 changed files with 36 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

34
kernel/sched/cpupri.c
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@@ -24,17 +24,37 @@
*/
#include "sched.h"
/* Convert between a 140 based task->prio, and our 100 based cpupri */
/*
* 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
*/
static int convert_prio(int prio)
{
int cpupri;
if (prio == CPUPRI_INVALID)
cpupri = CPUPRI_INVALID;
else if (prio >= MAX_RT_PRIO)
cpupri = CPUPRI_NORMAL;
else
cpupri = MAX_RT_PRIO - prio - 1;
switch (prio) {
case CPUPRI_INVALID:
cpupri = CPUPRI_INVALID; /* -1 */
break;
case 0 ... 98:
cpupri = MAX_RT_PRIO-1 - prio; /* 1 ... 99 */
break;
case MAX_RT_PRIO-1:
cpupri = CPUPRI_NORMAL; /* 0 */
break;
}
return cpupri;
}