[ltp] rtc: lost some interrupts at 1024Hz

[martin kot]

Hi,

I'm using  a program that depends on RTC timing while sending network
packets. Once the application runs dmesg is filled with:

"rtc: lost some interrupts at 1024Hz"

This message is then repeated thousands of times and entirely fills
the console. The performance of this application is very low compared
with runs on other computers. I suspect this to be either a kernel or
an IRQ-assignment issue, but I haven't figured it out.

Below is some information and what I've tried so far:

- The computer is a thinkpad X60, BIOS 2.10 (latest as of April 23rd 2007)
- Distribution is Debian testing, stock 2.6.20 kernel right now. Tried
2.6.15, 2.6.18 with the same result.
- I have tried different kernel parameters on boot, noapic, nolapic,
acpi=off, pci=assign-busses, pci=routeirq but it didn't help.
- When booting with acpi=off I couldn't use any of my external network
adapters pcmcia/usb. I guess this is not a solution.
- Noticed the possibility to reserve PCI irqs in the BIOS, but RTC
runs on irq 8 anyway. This didn't help, but maybe I should look more
into it.
- Tried to unload the rtc module and load genrtc instead, but the app
explicitly wants rtc which gives higher performance.
- Setting /proc/sys/dev/rtc/max-user-freq to 4096 didn't help. I guess
this just makes it worse.

For a comparison, I tried the application on a thinkpad X20 and a
600E. Same distribution and kernel versions as above, no problems at
all :(

I'm not sure how to proceed from here, hopefully someone has a clue.
I'll supply any information about the setup if needed.

--
Martin