Re: [discuss] x86-64: double timer interrupts in recent 2.4.x
From: Milan Gabor
Date: Mon Jun 21 2004 - 05:48:27 EST
Hi!
I have Suse 9.0 and dual Opteron on MSI K8T Master 2 motherboard.
I also get interrupts only on one cpu and my clock is ticking strange,
so I have to synchronize it with NTP server frequently.
This is from my system:
CPU0 CPU1
0: 30434 16139843 IO-APIC-edge timer
1: 944 0 IO-APIC-edge keyboard
2: 0 0 XT-PIC cascade
14: 30 1 IO-APIC-edge ide0
16: 657371 0 IO-APIC-level eth0
20: 261267 0 IO-APIC-level libata
NMI: 694146 873271
LOC: 16167676 16167576
ERR: 1
MIS: 0
Linux www 2.4.21-226-smp #1 SMP Tue Jun 15 09:14:10 UTC 2004 x86_64
x86_64 x86_64 GNU/Linux
I am also running irq_balance and acpi=off set from grub boot menu.
Without acpi=off system never boots.
Is there any solution, so clock will work OK and interrupts will be on
both CPUs?
MIlan
Peter Cordes wrote:
Nobody replied to this message on debian-amd64@xxxxxxxxx, or
discuss@xxxxxxxxxxx Hopefully I've found the right places to send this this
time around. Actually, Roland Fehrenbacher saw my message in a list archive
and mailed me to confirm that he saw the same double-speed clock problem on
two different machines, so it's not just Tyan S2880 boards. He suggested I
mail Andi and lkml, so here goes. (I haven't tested again with anything more
recent than 2.4.27-pre2, so if this is fixed, sorry.)
-----
I just noticed that on my Opteron cluster, the nodes that are running 64bit
kernels have their clocks ticking at double speed. This happens with
Linux 2.4.26, and 2.4.27-pre2, compiled with gcc 3.3.3 (Debian 20040401) in a
Debian pure64 chroot. Linux 2.4.25, compiled on Debian Woody + bi-arch gcc
3.3.2 20030908, does _not_ have the problem. The config options were pretty
much the same for all kernels, and all the kernels are plain vanilla flavour
from www.ca.kernel.org.
If I run ntpdate to set the clock, then 10 seconds later it will be 10
seconds fast. Running date(1), the system time advances 20 seconds in 10
seconds of real time. (I haven't done anything weird with adjtimex(8).)
time sleep 10 takes 5 seconds, but bash reports its real time as 10 seconds.
The timer interrupt counter is increasing at a rate of 200/real second, so
it seems like the system is getting timer interrupts twice as fast as it
should. (With 2.4.25, it is 100/sec, same as HZ).
Linux says it is using the PIT and TSC timers. I have HPET enabled in my
Linux config, but I guess Tyan's S2880 mobo doesn't have one. This is a
dual-Opteron 240 machine, BTW.
i386 Linux on the same machines has no problems with timekeeping. (But I
haven't tested versions later than 2.4.25 in legacy mode.)
I spent some time poking around the timer code that increments xtime, but I
guess the fact that the timer irqs are coming at double speed indicates that
the problem lies elsewhere. Maybe the code that sets up the timer?
$ uname -a
Linux node6.cs.dal.ca 2.4.26 #2 SMP Fri May 14 14:46:42 ADT 2004 x86_64 x86_64 x86_64 GNU/Linux
$ cat /proc/interrupts
CPU0 CPU1
0: 4415908 0 IO-APIC-edge timer
1: 2 0 IO-APIC-edge keyboard
2: 0 0 XT-PIC cascade
9: 0 0 IO-APIC-level acpi
14: 17861 1 IO-APIC-edge ide0
19: 0 0 IO-APIC-level usb-ohci, usb-ohci
24: 563942 0 IO-APIC-level eth0
25: 564331 0 IO-APIC-level eth1
NMI: 19097 19097
LOC: 2211090 2211095
ERR: 0
MIS: 0
Only CPU0 is getting the timer interrupt, but at least we know it's not
that both CPUs are getting the timer interrupt. (Both CPUs get 100 LOC:
(local APIC) interrupts/sec, but that happens on the non-buggy 2.4.25, too.)
Thanks for any help,
I'm not subscribed to the lkml, so please CC me on any followups.
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