Comment 52 for bug 838811

Hello,

I'm afraid this fix has the annoying side effect of reporting a higher than real load on idle systems. At least that's my conclusion after digging why my precise pangolin desktop was hardly getting below 0.5 even when idling.

Attached is the output of (ps waux; for i in 1 2 3; do uptime; vmstat -n 10 30; done; uptime; ps waux) | tee /tmp/idle.txt
during which I just watched time pass by and pressed <ctrl> a few times to prevent the blanker to kick in. The chrome process had 3 tabs opened (gmail, google reader and this bug's thread) and a fetchmail was triggered by cron every 5 minutes.

In summary, the vmstat never showed more than 3% cpu usage and uptime gave the following loads:
 15:35:53 up 22 min, 4 users, load average: 0.45, 0.46, 0.49
 15:40:43 up 26 min, 4 users, load average: 1.60, 0.87, 0.63
 15:45:33 up 31 min, 4 users, load average: 0.91, 1.00, 0.77
 15:50:23 up 36 min, 4 users, load average: 0.48, 0.68, 0.68

IMHO, 0.68 is a really high load for an idle system. :-)

The desktop was a fresh unity on an HP Elite 8100 quad core i5@3.2GHz with 4GB of RAM and running
Linux 3.2.0-24-generic #37-Ubuntu SMP Wed Apr 25 08:43:22 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux.

I'll try to look at the kernel/sched.c later to understand how this fix induced this behaviour.

Cheers !