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Subject: Re: [patch 2.6.16-mm2 10/9] sched throttle tree extract - kill
	interactive task feedback loop
From: Mike Galbraith <efault@gmx.de>
To: Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@osdl.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
       Peter Williams <pwil3058@bigpond.net.au>,
       Nick Piggin <nickpiggin@yahoo.com.au>, Con Kolivas <kernel@kolivas.org>
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Date: Wed, 05 Apr 2006 19:38:51 +0200
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Greetings,

The patch below stops interactive tasks from feeding off each other
during round-robin.

With this 10th patch in place, a busy server with _default_ throttle
settings (ie tunables may now be mostly unneeded) looks like this:

[root]:# w
 18:38:00 up 23 min,  2 users,  load average: 10.07, 9.94, 7.50
USER     TTY        LOGIN@   IDLE   JCPU   PCPU  WHAT
root     tty1      18:15   22:12  30.89s 30.84s  top d1
root     pts/0     18:20    0.00s  0.07s  0.00s  w
[root]:# time netstat|grep :81|wc -l
   1758

real    0m0.304s
user    0m0.144s
sys     0m0.135s
[root]:# time netstat|grep :81|wc -l
   1776

real    0m0.306s
user    0m0.118s
sys     0m0.163s
[root]:# time netstat|grep :81|wc -l
   1799

real    0m0.493s
user    0m0.146s
sys     0m0.141s
[root]:#

My desktop still feels just peachy.

Signed-off-by: Mike Galbraith <efault@gmx.de>

--- linux-2.6.16-mm2/kernel/sched.c-9.export_tunables	2006-03-31 13:37:09.000000000 +0200
+++ linux-2.6.16-mm2/kernel/sched.c	2006-04-05 19:22:01.000000000 +0200
@@ -3480,7 +3480,7 @@ go_idle:
 	queue = array->queue + idx;
 	next = list_entry(queue->next, task_t, run_list);
 
-	if (!rt_task(next) && interactive_sleep(next->sleep_type)) {
+	if (!TASK_INTERACTIVE(next) && interactive_sleep(next->sleep_type)) {
 		unsigned long long delta = now - next->timestamp;
 		if (unlikely((long long)(now - next->timestamp) < 0))
 			delta = 0;