svn commit: r228718 - head/sys/kern

[Andriy Gapon]

Author: avg
Date: Mon Dec 19 20:01:21 2011
New Revision: 228718
URL: http://svn.freebsd.org/changeset/base/228718

Log:
  ule: ensure that batch timeshare threads are scheduled fairly
  
  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 at m5p.com>
  Reviewed by:	jhb
  Tested by:	George Mitchell <george at m5p.com> (earlier version)
  MFC after:	1 week

Modified:
  head/sys/kern/sched_ule.c

Modified: head/sys/kern/sched_ule.c
==============================================================================
--- head/sys/kern/sched_ule.c	Mon Dec 19 19:02:36 2011	(r228717)
+++ head/sys/kern/sched_ule.c	Mon Dec 19 20:01:21 2011	(r228718)
@@ -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, i
 	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 thr
 		 * 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