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libmthread: add possibility to randomize scheduler

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This commit is contained in:
Thomas Veerman 2012-12-11 19:53:08 +00:00
parent 3de8d1cf6e
commit 93103f497f
2 changed files with 51 additions and 9 deletions
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2
lib/libmthread/global.h
View File

@ -8,7 +8,7 @@
#include <sys/types.h>
#include <sys/signal.h>
#define MTHREAD_RND_SCHED 0 /* Enable/disable random scheduling */
#define NO_THREADS 4
#define MAX_THREAD_POOL 1024
#define STACKSZ 4096

58
lib/libmthread/queue.c
View File

@ -95,14 +95,55 @@ mthread_queue_t *queue; /* Queue we want a thread from */
{
/* Get the first thread in this queue, if there is one. */
mthread_thread_t thread;
mthread_tcb_t *tcb;
mthread_tcb_t *tcb, *random_tcb, *prev;
int count = 0, offset_id = 0, picked_random = 0;
/* Calculate thread id from queue head */
if (queue->mq_head == NULL) thread = NO_THREAD;
else if (queue->mq_head == &mainthread) thread = MAIN_THREAD;
else thread = (queue->mq_head->m_tid);
tcb = queue->mq_head;
if (thread != NO_THREAD) { /* i.e., this queue is not empty */
if (MTHREAD_RND_SCHED) {
/* Count items on queue */
random_tcb = queue->mq_head;
if (random_tcb != NULL) {
do {
count++;
random_tcb = random_tcb->m_next;
} while (random_tcb != NULL);
}
if (count > 1) {
picked_random = 1;
/* Get random offset */
offset_id = random() % count;
/* Find offset in queue */
random_tcb = queue->mq_head;
prev = random_tcb;
while (--offset_id > 0) {
prev = random_tcb;
random_tcb = random_tcb->m_next;
}
/* Stitch head and tail together */
prev->m_next = random_tcb->m_next;
/* Fix head and tail */
if (queue->mq_head == random_tcb)
queue->mq_head = random_tcb->m_next;
if (queue->mq_tail == random_tcb)
queue->mq_tail = prev;
tcb = random_tcb;
}
}
/* Retrieve thread id from tcb */
if (tcb == NULL) thread = NO_THREAD;
else if (tcb == &mainthread) thread = MAIN_THREAD;
else thread = (tcb->m_tid);
/* If we didn't pick a random thread and queue is not empty... */
if (!picked_random && thread != NO_THREAD) {
tcb = queue->mq_head;
if (queue->mq_head == queue->mq_tail) {
/* Queue holds only one thread */
@ -111,10 +152,11 @@ mthread_queue_t *queue; /* Queue we want a thread from */
/* Second thread in line is the new first */
queue->mq_head = queue->mq_head->m_next;
}
tcb->m_next = NULL; /* This thread is no longer part of a queue */
}
if (tcb != NULL)
tcb->m_next = NULL; /* This thread is no longer part of a queue */
return(thread);
}