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SubjectRe: [PATCH] x86-64 highres/dyntick support
Date
On Sunday 06 May 2007 21:58:47 Thomas Gleixner wrote:
> I'm pleased to announce the first cut of the final x86_64
> highres/dyntick support, which I did based on Chris Wright's patch set,
> which is again based on Arjan van de Ven's initial work:

I've noticed a few problems with this patch series, which I manually (without
difficulty) ported to 2.6.22-rc1.
Firstly, the output of /proc/interrupts looks a bit strange. NO_HZ isn't
enabled, just high resolution timers. HZ was set to 1000.

alistair@damocles:~$ cat /proc/interrupts
CPU0 CPU1
0: 195 0 IO-APIC-edge timer
1: 21 13698 IO-APIC-edge i8042
8: 0 0 IO-APIC-edge rtc
9: 0 0 IO-APIC-fasteoi acpi
14: 117 51178 IO-APIC-edge libata
15: 0 0 IO-APIC-edge libata
18: 455 449373 IO-APIC-fasteoi lan-sky, EMU10K1
19: 0 3 IO-APIC-fasteoi yenta, ohci1394
20: 220 86188 IO-APIC-fasteoi ohci_hcd:usb2
21: 0 26 IO-APIC-fasteoi ehci_hcd:usb1
22: 0 273 IO-APIC-fasteoi sata_nv
23: 928 507781 IO-APIC-fasteoi sata_nv, lan
NMI: 0 0
LOC: 4723272 4797930
ERR: 0

Only 195 timer interrupts? I only see this on an AMD Opteron, it doesn't occur
on an Intel Core 2 Duo. Mainline reports this counter regularly increasing
with or without the acpi_pm clocksource loaded.

Secondly, /proc/cpuinfo seems to be broken:

alistair@damocles:~$ cat /proc/cpuinfo | grep MHz
cpu MHz : 210779.550
cpu MHz : 210779.550
Unless my CPU is just under 80 times faster than it used to be, these numbers
are incorrect. I expect 2700.50, or something similar. cpufreq isn't compiled
in.

Finally, and possibly related, the dmesg timestamps seem to be totally broken.
Apparently my machine booted in less than 1 second, with the last messages
as:

[ 0.607862] bridge: topology change detected, propagating
[ 0.607862] bridge: port 2(lan-sky) entering forwarding state
[ 0.830472] Linux agpgart interface v0.102 (c) Dave Jones

Of course, all of these problems might be PEBKAC, but I'm sceptical.

Find the kernel config, updated patch (for 2.6.22-rc1), dmesg, contents
of /proc/interrupts and /proc/cpuinfo here:

http://devzero.co.uk/~alistair/2.6.22-rc1-hrt/

--
Cheers,
Alistair.

Final year Computer Science undergraduate.
1F2 55 South Clerk Street, Edinburgh, UK.
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