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Date: Sat, 29 Mar 2003 21:23:30 -0800
From: Andrew Morton <akpm@digeo.com>
To: Tom Sightler <ttsig@tuxyturvy.com>
Cc: rml@tech9.net, linux-kernel@vger.kernel.org
Subject: Re: Bad interactive behaviour in 2.5.65-66 (sched.c)
Message-Id: <20030329212330.225a96b6.akpm@digeo.com>
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Tom Sightler <ttsig@tuxyturvy.com> wrote:
>
> On my system I get a starvation issue with just about any CPU intensive
> task.  For example if create a bzip'd tar file from the linux kernel
> source with the command:
> 
> tar cvp linux | bzip2 -9 > linux.tar.bz2
> 

Ingo has determined that Linus's backboost trick is causing at least some
of these problems. Please test and report upon the below patch.

I have another workload which is showing starvation with or without this
patch - it is the bitkeeper verification step in a `bk clone' on a
uniprocessor kernel.  Still poking at that one.






From: Ingo Molnar <mingo@elte.hu>

the patch below fixes George's setiathome problems (as expected).  It
essentially turns off Linus' improvement, but i dont think it can be fixed
sanely.

the problem with setiathome is that it displays something every now and
then - so it gets a backboost from X, and hovers at a relatively high
priority.



 kernel/sched.c |   13 +------------
 1 files changed, 1 insertion(+), 12 deletions(-)

diff -puN kernel/sched.c~sched-interactivity-backboost-revert kernel/sched.c
--- 25/kernel/sched.c~sched-interactivity-backboost-revert	2003-03-28 22:30:08.000000000 -0800
+++ 25-akpm/kernel/sched.c	2003-03-28 22:30:08.000000000 -0800
@@ -379,19 +379,8 @@ static inline int activate_task(task_t *
 		 * boosting tasks that are related to maximum-interactive
 		 * tasks.
 		 */
-		if (sleep_avg > MAX_SLEEP_AVG) {
-			if (!in_interrupt()) {
-				sleep_avg += current->sleep_avg - MAX_SLEEP_AVG;
-				if (sleep_avg > MAX_SLEEP_AVG)
-					sleep_avg = MAX_SLEEP_AVG;
-
-				if (current->sleep_avg != sleep_avg) {
-					current->sleep_avg = sleep_avg;
-					requeue_waker = 1;
-				}
-			}
+		if (sleep_avg > MAX_SLEEP_AVG)
 			sleep_avg = MAX_SLEEP_AVG;
-		}
 		if (p->sleep_avg != sleep_avg) {
 			p->sleep_avg = sleep_avg;
 			p->prio = effective_prio(p);

_

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