linux-kernel - driver or calculation of load average wrong ?

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Message-ID: <4CAF1310.2050400@wincor-nixdorf.com>
Date:	Fri, 08 Oct 2010 14:48:16 +0200
From:	Frank Salomon <frank.salomon@...cor-nixdorf.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: driver or calculation of load average wrong ?

Hello All,

I have the following configuration:
- CentOS 5
- kernel 2.6.20.1
- My own driver in a kernel_thread:
		while ( 1 ){
			printk ( KERN_INFO "go sleep, %lu\n", jiffies );
			current -> state = TASK_UNINTERRUPTIBLE;
			schedule_timeout ( msecs_to_jiffies(4000) );
			printk ( KERN_INFO "wakeup, %lu\n", jiffies );
		}

Each time I load the driver, the load average in /proc/loadavg reached:
	$ cat /proc/loadavg
	0.99 0.62 0.26 1/47 2868
Without my driver:
	$ cat /proc/loadavg
	0.03 0.03 0.00 1/47 2867

I changed nr_active(void) in kernel/sched.c:
unsigned long nr_active(void)
{
         unsigned long i, running = 0, uninterruptible = 0;

         for_each_online_cpu(i) {
                 running += cpu_rq(i)->nr_running;
                 uninterruptible += cpu_rq(i)->nr_uninterruptible;
         }

         if (unlikely((long)uninterruptible < 0))
                 uninterruptible = 0;

// original:     return running + uninterruptible;
         return running;
}

Driver loaded or not:
	$ cat /proc/loadavg
	0.03 0.03 0.00 1/47 2867

Any help or comments would be really great?

Best regards, thanks, Frank

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