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Merge pull request #14722 from bergzand/pr/sched/runqueue_clz

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sched: Reverse runqueue order when CLZ is available
This commit is contained in:
Kaspar Schleiser 2020-09-01 22:57:30 +02:00 committed by GitHub
commit f68f19a73f
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 37 additions and 3 deletions
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40
core/sched.c
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@ -83,6 +83,40 @@ static void (*sched_cb) (kernel_pid_t active_thread,
kernel_pid_t next_thread) = NULL; kernel_pid_t next_thread) = NULL;
#endif #endif
/* Depending on whether the CLZ instruction is available, the order of the
* runqueue_bitcache is reversed. When the instruction is available, it is
* faster to determine the MSBit set. When it is not available it is faster to
* determine the LSBit set. These functions abstract the runqueue modifications
* and readout away, switching between the two orders depending on the CLZ
* instruction availability
*/
static inline void _set_runqueue_bit(thread_t *process)
{
#if defined(BITARITHM_HAS_CLZ)
runqueue_bitcache |= BIT31 >> process->priority;
#else
runqueue_bitcache |= 1 << process->priority;
#endif
}
static inline void _clear_runqueue_bit(thread_t *process)
{
#if defined(BITARITHM_HAS_CLZ)
runqueue_bitcache &= ~(BIT31 >> process->priority);
#else
runqueue_bitcache &= ~(1 << process->priority);
#endif
}
static inline unsigned _get_prio_queue_from_runqueue(void)
{
#if defined(BITARITHM_HAS_CLZ)
return 31 - bitarithm_msb(runqueue_bitcache);
#else
return bitarithm_lsb(runqueue_bitcache);
#endif
}
static void _unschedule(thread_t *active_thread) static void _unschedule(thread_t *active_thread)
{ {
if (active_thread->status == STATUS_RUNNING) { if (active_thread->status == STATUS_RUNNING) {
@ -123,7 +157,7 @@ int __attribute__((used)) sched_run(void)
sched_context_switch_request = 0; sched_context_switch_request = 0;
int nextrq = bitarithm_lsb(runqueue_bitcache); unsigned nextrq = _get_prio_queue_from_runqueue();
thread_t *next_thread = container_of(sched_runqueues[nextrq].next->next, thread_t *next_thread = container_of(sched_runqueues[nextrq].next->next,
thread_t, rq_entry); thread_t, rq_entry);
@ -178,7 +212,7 @@ void sched_set_status(thread_t *process, thread_status_t status)
process->pid, process->priority); process->pid, process->priority);
clist_rpush(&sched_runqueues[process->priority], clist_rpush(&sched_runqueues[process->priority],
&(process->rq_entry)); &(process->rq_entry));
runqueue_bitcache |= 1 << process->priority; _set_runqueue_bit(process);
} }
} }
else { else {
@ -189,7 +223,7 @@ void sched_set_status(thread_t *process, thread_status_t status)
clist_lpop(&sched_runqueues[process->priority]); clist_lpop(&sched_runqueues[process->priority]);
if (!sched_runqueues[process->priority].next) { if (!sched_runqueues[process->priority].next) {
runqueue_bitcache &= ~(1 << process->priority); _clear_runqueue_bit(process);
} }
} }
} }