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

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Message-ID: <68676e00702211519k68104e31ia2ae38a14eb27c1f@mail.gmail.com>
Date:	Thu, 22 Feb 2007 00:19:41 +0100
From:	"Luca Tettamanti" <kronos.it@...il.com>
To:	tglx@...utronix.de
Cc:	linux-kernel@...r.kernel.org
Subject: Re: NO_HZ: timer interrupt stuck [Re: Linux 2.6.21-rc1]

On 2/22/07, Thomas Gleixner <tglx@...utronix.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
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