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ule: ensure that batch timeshare threads are scheduled fairly

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With the previous code, if the range of priorities for timeshare batch
threads was greater than RQ_NQS, then the threads with low priorities in
the part of the range above RQ_NQS would be scheduled to the run-queues
as if they had high priorities at the beginning of the range.
In other words, threads with a nice level of +N could be scheduled as
if they had a nice level of -M.

Reported by:	George Mitchell <george@m5p.com>
Reviewed by:	jhb
Tested by:	George Mitchell <george@m5p.com> (earlier version)
MFC after:	1 week
This commit is contained in:
avg 2011-12-19 20:01:21 +00:00
parent 291f526f0d
commit 8d78bfbee0
1 changed files with 2 additions and 2 deletions
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4
sys/kern/sched_ule.c
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@ -125,6 +125,7 @@ static struct td_sched td_sched0;
*/
#define PRI_TIMESHARE_RANGE (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
#define PRI_INTERACT_RANGE ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2)
#define PRI_BATCH_RANGE (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE)
#define PRI_MIN_INTERACT PRI_MIN_TIMESHARE
#define PRI_MAX_INTERACT (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1)
@ -416,7 +417,6 @@ sched_shouldpreempt(int pri, int cpri, int remote)
return (0);
}
#define TS_RQ_PPQ (((PRI_MAX_BATCH - PRI_MIN_BATCH) + 1) / RQ_NQS)
/*
* Add a thread to the actual run-queue. Keeps transferable counts up to
* date with what is actually on the run-queue. Selects the correct
@ -449,7 +449,7 @@ tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
* realtime. Use the whole queue to represent these values.
*/
if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
pri = (pri - PRI_MIN_BATCH) / TS_RQ_PPQ;
pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
pri = (pri + tdq->tdq_idx) % RQ_NQS;
/*
* This effectively shortens the queue by one so we