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Date:      Sat, 22 Oct 2011 13:28:17 +0300
From:      Ivan Klymenko <fidaj@ukr.net>
To:        freebsd-current@freebsd.org
Subject:   Increase the degree of interactivity ULE scheduler
Message-ID:  <20111022132817.35db5ccd@nonamehost.>

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Hello people!

I have:
CPU: Intel(R) Core(TM)2 Duo CPU     T7250  @ 2.00GHz (1994.48-MHz K8-class CPU)
FreeBSD 10.0-CURRENT r226607 amd64

For example during the building of the port lang/gcc46 in four streams (-j 4) with a heavy load on the processor - use the system was nearly impossible - responsiveness was terrible - the mouse cursor sometimes froze on the spot a few seconds...

I managed to achieve a significant increase in the degree of interactivity ULE scheduler due to the following changes:
##########################
--- sched_ule.c.orig	2011-10-22 11:40:30.000000000 +0300
+++ sched_ule.c	2011-10-22 12:25:05.000000000 +0300
@@ -2119,6 +2119,14 @@
 
 	THREAD_LOCK_ASSERT(td, MA_OWNED);
 	tdq = TDQ_SELF();
+	if (td->td_pri_class & PRI_FIFO_BIT)
+		return;
+	ts = td->td_sched;
+	/*
+	 * We used up one time slice.
+	 */
+	if (--ts->ts_slice > 0)
+		return;
 #ifdef SMP
 	/*
 	 * We run the long term load balancer infrequently on the first cpu.
@@ -2144,9 +2152,6 @@
 		if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
 			tdq->tdq_ridx = tdq->tdq_idx;
 	}
-	ts = td->td_sched;
-	if (td->td_pri_class & PRI_FIFO_BIT)
-		return;
 	if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
 		/*
 		 * We used a tick; charge it to the thread so
@@ -2157,11 +2162,6 @@
 		sched_priority(td);
 	}
 	/*
-	 * We used up one time slice.
-	 */
-	if (--ts->ts_slice > 0)
-		return;
-	/*
 	 * We're out of time, force a requeue at userret().
 	 */
 	ts->ts_slice = sched_slice;
##########################

What do you think about this?

Thanks!
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