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* Changed the affine scheduler to have more or less the same characteristics

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as the BeOS scheduler. This makes MediaPlayer playback much better, as high
  priority threads could lose their quantum to a worker thread twice in a row
  with 4% probability before.
* I did not yet change the simple scheduler as well yet; maybe this isn't the
  final one either.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@33965 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Axel Dörfler 2009-11-09 19:00:42 +00:00
parent 7843ca4c64
commit 7249de5e61
1 changed files with 31 additions and 12 deletions
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37
src/system/kernel/scheduler/scheduler_affine.cpp
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@ -9,6 +9,7 @@
* Distributed under the terms of the NewOS License.
*/
/*! The thread scheduler */
@ -49,6 +50,7 @@ const int32 kMaxTrackingQuantums = 5;
const bigtime_t kMinThreadQuantum = 3000;
const bigtime_t kMaxThreadQuantum = 10000;
struct scheduler_thread_data {
scheduler_thread_data(void)
{
@ -202,6 +204,9 @@ affine_enqueue_in_run_queue(struct thread *thread)
return false;
}
/*! Dequeues the thread after the given \a prevThread from the run queue.
*/
static inline struct thread *
dequeue_from_run_queue(struct thread *prevThread, int32 currentCPU)
{
@ -219,6 +224,7 @@ dequeue_from_run_queue(struct thread *prevThread, int32 currentCPU)
return resultThread;
}
/*! Looks for a possible thread to grab/run from another CPU.
Note: thread lock must be held when entering this function
*/
@ -393,17 +399,30 @@ affine_reschedule(void)
if (nextThread->priority >= B_FIRST_REAL_TIME_PRIORITY)
break;
// skip normal threads sometimes (roughly 20%)
if (_rand() > 0x1a00)
// find next thread with lower priority
struct thread *lowerNextThread = nextThread->queue_next;
struct thread *lowerPrevThread = nextThread;
int32 priority = nextThread->priority;
while (lowerNextThread != NULL
&& priority == lowerNextThread->priority) {
lowerPrevThread = lowerNextThread;
lowerNextThread = lowerNextThread->queue_next;
}
if (lowerNextThread == NULL)
break;
// skip until next lower priority
int32 priority = nextThread->priority;
do {
prevThread = nextThread;
nextThread = nextThread->queue_next;
} while (nextThread->queue_next != NULL
&& priority == nextThread->queue_next->priority);
int32 priorityDiff = priority - lowerNextThread->priority;
if (priorityDiff > 15)
break;
// skip normal threads sometimes
// (twice as probable per priority level)
if ((_rand() >> (15 - priorityDiff)) != 0)
break;
nextThread = lowerNextThread;
prevThread = lowerPrevThread;
}
TRACE(("dequeuing thread %ld from cpu %ld\n", nextThread->id,