Re: 2.6.33 & 2.6.34-rc6: Huge number of Load Balancing tick wakeups.

[Nigel Cunningham <ncunningham@crca.org.au>]

Hi again.

On 09/05/10 05:16, Len Brown wrote:
> What do you see if vmware is not present?
> What do you see if you boot single user mode,
> how about with maxcpusx=1?

Repeated the tests, just booting into X (xfce) - except for the init S 
test. No programs were started and wifi was turned off.

1) No vmware (etc)

Cn                Avg residency
C0 (cpu running)        ( 3.7%)
polling           0.0ms ( 0.0%)
C1 mwait          0.0ms ( 0.0%)
C2 mwait          0.1ms ( 0.3%)
C4 mwait          5.4ms (96.0%)
P-states (frequencies)
Turbo Mode     1.4%
   2.21 Ghz     0.0%
   1.60 Ghz     0.0%
   1200 Mhz     0.0%
    800 Mhz    98.6%
Wakeups-from-idle per second : 202.7    interval: 15.0s
no ACPI power usage estimate available
Top causes for wakeups:
   56.1% (128.5)   [kernel scheduler] Load balancing tick
   13.1% ( 30.1)   [extra timer interrupt]
    6.9% ( 15.9)   [ata_piix] <interrupt>

2) Above + maxcpus=1

Cn                Avg residency
C0 (cpu running)        ( 4.0%)
polling           0.0ms ( 0.0%)
C1 mwait          0.0ms ( 0.0%)
C2 mwait          0.4ms ( 0.2%)
C4 mwait         16.0ms (95.9%)
P-states (frequencies)
Turbo Mode     6.0%
   2.21 Ghz     0.0%
   1.60 Ghz     0.0%
   1200 Mhz     0.0%
    800 Mhz    94.0%
Wakeups-from-idle per second : 64.5     interval: 15.0s
no ACPI power usage estimate available
Top causes for wakeups:
   39.6% ( 46.3)   [kernel scheduler] Load balancing tick
   12.3% ( 14.3)   [ata_piix] <interrupt>

(No idea why you need a load balancing tick with one core!)

3) Init S, without maxcpus=1

Cn                Avg residency
C0 (cpu running)        ( 0.0%)
polling           0.0ms ( 0.0%)
C1 mwait          0.0ms ( 0.0%)
C2 mwait          0.1ms ( 0.0%)
C4 mwait         48.9ms (100.0%)
P-states (frequencies)
Turbo Mode     0.0%
   2.21 Ghz     0.0%
   1.60 Ghz     0.0%
   1200 Mhz     0.0%
    800 Mhz   100.0%
Wakeups-from-idle per second : 21.4     interval: 15.0s
no ACPI power usage estimate available
Top causes for wakeups:
   33.5% ( 10.3)   [kernel core] hrtimer_start (tick_sched_timer)
   16.1% (  4.9)   [kernel core] cursor_timer_handler (cursor_timer_handler)
   15.9% (  4.9)   [kernel scheduler] Load balancing tick
   12.8% (  3.9)   [kernel core] usb_hcd_poll_rh_status (rh_timer_func)
    9.3% (  2.9)   [ahci] <interrupt>

I also tried the patch Dominik provided, and it didn't seem to make a 
difference:

P-states (frequencies)
Turbo Mode     3.7%
   2.21 Ghz     0.0%
   1.60 Ghz     0.0%
   1200 Mhz     0.6%
    800 Mhz    95.7%
Wakeups-from-idle per second : 236.7    interval: 15.0s
no ACPI power usage estimate available
Top causes for wakeups:
   55.4% (119.7)   [kernel scheduler] Load balancing tick
    9.7% ( 20.9)   skype
    7.7% ( 16.5)   [ata_piix] <interrupt>

Regards,

Nigel