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kernel: support for more than 32 total priorities

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In addition to more priorities taking more memory to host them, finding
the next thread to run when it is not cached is slower since each extra
set of 32 priorities maps to a loop iteration. That loop is remove
entirely when the number of priorities is less than 32 (31 + the idle
thread).

Fixes ZEP-1303.

Change-Id: I3205df90d379a0f4456ff1d7f1aaa67ad2cddf15
Signed-off-by: Benjamin Walsh <benjamin.walsh@windriver.com>
This commit is contained in:
Benjamin Walsh 2016-11-18 15:35:05 -05:00 • committed by Anas Nashif
commit 358a53cb2f
5 changed files with 48 additions and 14 deletions
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25
kernel/unified/Kconfig
View file

@ -45,8 +45,16 @@ config NUM_COOP_PRIORITIES
This can be set to zero to disable cooperative scheduling. Cooperative
threads always preempt preemptible threads.
Each priority requires an extra 8 bytes of RAM. If there are more than
32 total priorities, an extra 4 bytes is required.
Each priority requires an extra 8 bytes of RAM. Each set of 32 extra
total priorities require an extra 4 bytes and add one possible
iteration to loops that search for the next thread to run.
The total number of priorities is
NUM_COOP_PRIORITIES + NUM_PREEMPT_PRIORITIES + 1
The extra one is for the idle thread, which must run at the lowest
priority, and be the only thread at that priority.
config NUM_PREEMPT_PRIORITIES
int
@ -58,11 +66,16 @@ config NUM_PREEMPT_PRIORITIES
This can be set to 0 to disable preemptible scheduling.
The idle thread is always installed as a preemptible thread of the
lowest priority.
Each priority requires an extra 8 bytes of RAM. Each set of 32 extra
total priorities require an extra 4 bytes and add one possible
iteration to loops that search for the next thread to run.
Each priority requires an extra 8 bytes of RAM. If there are more than
32 total priorities, an extra 4 bytes is required.
The total number of priorities is
NUM_COOP_PRIORITIES + NUM_PREEMPT_PRIORITIES + 1
The extra one is for the idle thread, which must run at the lowest
priority, and be the only thread at that priority.
config PRIORITY_CEILING
int

2
kernel/unified/include/kernel_structs.h
View file

@ -107,7 +107,7 @@ struct _ready_q {
struct k_thread *cache;
/* bitmap of priorities that contain at least one ready thread */
uint32_t prio_bmap[1];
uint32_t prio_bmap[K_NUM_PRIO_BITMAPS];
/* ready queues, one per priority */
sys_dlist_t q[K_NUM_PRIORITIES];

27
kernel/unified/include/ksched.h
View file

@ -167,17 +167,32 @@ static inline int _get_ready_q_q_index(int prio)
return prio + CONFIG_NUM_COOP_PRIORITIES;
}
#if (K_NUM_PRIORITIES > 32)
#error not supported yet
#endif
/* find out the currently highest priority where a thread is ready to run */
/* interrupts must be locked */
static inline int _get_highest_ready_prio(void)
{
uint32_t ready = _ready_q.prio_bmap[0];
int bitmap = 0;
uint32_t ready_range;
return find_lsb_set(ready) - 1 - CONFIG_NUM_COOP_PRIORITIES;
#if (K_NUM_PRIORITIES <= 32)
ready_range = _ready_q.prio_bmap[0];
#else
for (;; bitmap++) {
__ASSERT(bitmap < K_NUM_PRIO_BITMAPS, "prio out-of-range\n");
if (_ready_q.prio_bmap[bitmap]) {
ready_range = _ready_q.prio_bmap[bitmap];
break;
}
}
#endif
int abs_prio = (find_lsb_set(ready_range) - 1) + (bitmap << 5);
__ASSERT(abs_prio < K_NUM_PRIORITIES, "prio out-of-range\n");
return abs_prio - CONFIG_NUM_COOP_PRIORITIES;
}
/*

2
kernel/unified/include/nano_internal.h
View file

@ -28,6 +28,8 @@
#define K_NUM_PRIORITIES \
(CONFIG_NUM_COOP_PRIORITIES + CONFIG_NUM_PREEMPT_PRIORITIES + 1)
#define K_NUM_PRIO_BITMAPS ((K_NUM_PRIORITIES + 31) >> 5)
#ifndef _ASMLANGUAGE
#ifdef __cplusplus

6
kernel/unified/sched.c
View file

@ -348,7 +348,11 @@ k_tid_t k_current_get(void)
/* debug aid */
void _dump_ready_q(void)
{
K_DEBUG("bitmap: %x\n", _ready_q.prio_bmap[0]);
K_DEBUG("bitmaps: ");
for (int bitmap = 0; bitmap < K_NUM_PRIO_BITMAPS; bitmap++) {
K_DEBUG("%x", _ready_q.prio_bmap[bitmap]);
}
K_DEBUG("\n");
for (int prio = 0; prio < K_NUM_PRIORITIES; prio++) {
K_DEBUG("prio: %d, head: %p\n",
prio - CONFIG_NUM_COOP_PRIORITIES,