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From: Karsten Wiese <fzu@wemgehoertderstaat.de>
To: Andrew Morton <akpm@osdl.org>, Ingo Molnar <mingo@elte.hu>,
	Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: 2.6.20-rc6-mm2
Date: Mon, 29 Jan 2007 17:22:41 +0100	[thread overview]
Message-ID: <200701291722.41705.fzu@wemgehoertderstaat.de> (raw)
In-Reply-To: <20070129001207.71ea3470.akpm@osdl.org>

Hi,

with dynticks and highres_timers enabled, cpufreq_ondemand makes mess here on
an AMD64 UP.
cpufreq_ondemand assumes that jiffies advance at exactly the same pace as the
sum of all kstat_cpu(cpu).cpustat.* members.
This isn't the case here as dmesg output from patch below shows.

Is cpufreq_ondemand correct assuming
 "jiffies advance at exactly the same pace as the
  sum of all kstat_cpu(cpu).cpustat.* members"?
Or is "dynticks and highres_timers"'s behaviour of incrementing the
sum of  kstat_cpu(cpu).cpustat.* members faster than jiffies?

      Karsten



diff -pur rc6-mm2/drivers/cpufreq/cpufreq_ondemand.c rc6-mm2-kw/drivers/cpufreq/cpufreq_ondemand.c
--- rc6-mm2/drivers/cpufreq/cpufreq_ondemand.c	2007-01-29 10:40:39.000000000 +0100
+++ rc6-mm2-kw/drivers/cpufreq/cpufreq_ondemand.c	2007-01-29 11:37:08.000000000 +0100
@@ -370,7 +370,15 @@ static void dbs_check_cpu(struct cpu_dbs
 		if (tmp_idle_ticks < idle_ticks)
 			idle_ticks = tmp_idle_ticks;
 	}
-	load = (100 * (total_ticks - idle_ticks)) / total_ticks;
+	if (total_ticks < idle_ticks) {
+		static bool did;
+		if (!did) {
+			printk(KERN_INFO"%s: t%u < i%u\n", __FUNCTION__, total_ticks, idle_ticks);
+			did = true;
+		}
+		load = 0;
+	} else
+		load = (100 * (total_ticks - idle_ticks)) / total_ticks;
 
 	/* Check for frequency increase */
 	if (load > dbs_tuners_ins.up_threshold) {

  parent reply	other threads:[~2007-01-29 16:23 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-29  8:12 2.6.20-rc6-mm2 Andrew Morton
2007-01-29 11:02 ` 2.6.20-rc6-mm2 Jiri Kosina
2007-01-29 15:40   ` 2.6.20-rc6-mm2 Thomas Gleixner
2007-01-29 16:28     ` 2.6.20-rc6-mm2 Jiri Kosina
2007-01-30 10:27     ` 2.6.20-rc6-mm2 Maciej Rutecki
2007-01-29 11:21 ` [-mm patch] BUG at net/sunrpc/svc.c:128 (was Re: 2.6.20-rc6-mm2) Frederik Deweerdt
2007-01-29 17:32   ` Andrew Morton
2007-01-29 17:49     ` Christoph Lameter
2007-01-30 14:17       ` Frederik Deweerdt
2007-01-29 16:22 ` Karsten Wiese [this message]
2007-01-29 16:38   ` 2.6.20-rc6-mm2 Thomas Gleixner
2007-01-29 17:28 ` 2.6.20-rc6-mm2 - modules_install error Matthew Frost
2007-01-29 21:37 ` 2.6.20-rc6-mm2 Laurent Riffard
2007-01-29 21:59 ` [PATCH] compile and link utsname_sysctl.o Laurent Riffard
2007-01-30 15:11   ` Eric W. Biederman
2007-01-30 16:26     ` Laurent Riffard
2007-02-06 22:13 ` [-mm patch] make kernel/time/timer_stats.c:nr_entries static Adrian Bunk
2007-02-06 22:15   ` Ingo Molnar

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