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Reworked the way thread_yield() works: just setting the thread to B_LOWEST_ACTIVE_PRIORITY

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for one quantum wasn't really a good idea, as this could get quite expensive for the thread
(depending on the system load, it might have taken a long time until the thread was scheduled
again, no matter what priority it was).
Also, calling thread_yield() in a loop would have taken 100% CPU time.
Now, we sort the thread into the queue as with any other thread, but we'll ignore it once.
This now guarantees an actual context switch, as well as a much fairer rescheduling policy
for threads calling that function.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@20077 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Axel Dörfler 2007-02-06 02:29:17 +00:00
parent 8c31a369ab
commit eb117b4bfd
3 changed files with 16 additions and 6 deletions
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1
headers/private/kernel/thread_types.h
View File

@ -142,6 +142,7 @@ struct thread {
struct sigaction sig_action[32];
bool in_kernel;
bool was_yielded;
struct {
sem_id blocking;

10
src/system/kernel/scheduler.cpp
View File

@ -1,5 +1,5 @@
/*
* Copyright 2002-2006, Axel Dörfler, axeld@pinc-software.de.
* Copyright 2002-2007, Axel Dörfler, axeld@pinc-software.de.
* Copyright 2002, Angelo Mottola, a.mottola@libero.it.
* Distributed under the terms of the MIT License.
*
@ -189,6 +189,13 @@ scheduler_reschedule(void)
} else {
// select next thread from the run queue
while (nextThread && nextThread->priority > B_IDLE_PRIORITY) {
if (oldThread == nextThread && nextThread->was_yielded) {
// ignore threads that called thread_yield() once
nextThread->was_yielded = false;
prevThread = nextThread;
nextThread = nextThread->queue_next;
}
// always extract real time threads
if (nextThread->priority >= B_FIRST_REAL_TIME_PRIORITY)
break;
@ -222,6 +229,7 @@ scheduler_reschedule(void)
nextThread->state = B_THREAD_RUNNING;
nextThread->next_state = B_THREAD_READY;
oldThread->was_yielded = false;
// track kernel time (user time is tracked in thread_at_kernel_entry())
bigtime_t now = system_time();

11
src/system/kernel/thread.c
View File

@ -214,6 +214,7 @@ create_thread_struct(const char *name, thread_id threadID)
thread->sig_block_mask = 0;
memset(thread->sig_action, 0, 32 * sizeof(struct sigaction));
thread->in_kernel = true;
thread->was_yielded = false;
thread->user_time = 0;
thread->kernel_time = 0;
thread->last_time = 0;
@ -915,13 +916,13 @@ thread_exit(void)
struct thread_debug_info debugInfo;
team_id teamID = team->id;
if (!are_interrupts_enabled())
dprintf("thread_exit() called with interrupts disabled!\n");
TRACE(("thread 0x%lx exiting %s w/return code 0x%x\n", thread->id,
thread->exit.reason == THREAD_RETURN_INTERRUPTED ? "due to signal" : "normally",
(int)thread->exit.status));
if (!are_interrupts_enabled())
panic("thread_exit() called with interrupts disabled!\n");
// boost our priority to get this over with
thread->priority = thread->next_priority = B_URGENT_DISPLAY_PRIORITY;
@ -1298,8 +1299,8 @@ thread_yield(void)
state = disable_interrupts();
GRAB_THREAD_LOCK();
// just add the thread at the end of the run queue
thread->next_priority = B_LOWEST_ACTIVE_PRIORITY;
// mark the thread as yielded, so it will not be scheduled next
thread->was_yielded = true;
scheduler_reschedule();
RELEASE_THREAD_LOCK();