Re: NO_HZ: timer interrupt stuck [Re: Linux 2.6.21-rc1]

Luca Tettamanti
2007-02-21T23:19:43Z

On 2/22/07, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Thu, 2007-02-22 at 00:04 +0100, Luca Tettamanti wrote:
> > Hi Thomas,
> > I'm testing NO_HZ on my machines. On the laptop I see that the timer
> > interrupt counter is incremented (though slower than HZ). This machine
> > is running UP kernel.
> >
> > On my desktop I see this:
> >
> > CPU0 CPU1
> > 0: 114 0 IO-APIC-edge timer
> > 1: 1624 10771 IO-APIC-edge i8042
> > 6: 3 0 IO-APIC-edge floppy
> > 7: 0 0 IO-APIC-edge parport0
> > 9: 0 0 IO-APIC-fasteoi acpi
> > 12: 40111 184047 IO-APIC-edge i8042
> > 16: 75624 998858 IO-APIC-fasteoi radeon@pci:0000:01:00.0, uhci_hcd:usb1
> > 17: 0 0 IO-APIC-fasteoi uhci_hcd:usb4
> > 18: 711 5487 IO-APIC-fasteoi ide1, libata, ehci_hcd:usb7, uhci_hcd:usb3
> > 19: 617 2254 IO-APIC-fasteoi libata, uhci_hcd:usb2
> > 20: 0 0 IO-APIC-fasteoi ehci_hcd:usb6, uhci_hcd:usb5
> > 21: 2483869 0 IO-APIC-fasteoi eth0
> > 22: 2 0 IO-APIC-fasteoi ohci1394
> > 218: 28872 360643 PCI-MSI-edge HDA Intel
> > 219: 32932 138196 PCI-MSI-edge libata
> > NMI: 0 0
> > LOC: 2761191 2827539
> > ERR: 0
> > MIS: 0
> >
> > Interrupt 0 is stuck at 114 (the number is consistent across reboots). I
> > don't experience any problem, time is running fine. Still it's strange
> > that the timer is doing nothing; maybe something other than the PIT is
> > used for time keeping?
>
> Yes, we switch away from PIT and use the local APIC timer. (LOC)

Ok, thanks for the clarification.

Luca