Re: 2.5.69 Interrupt Latency

[Paul Fulghum <paulkf@microgate.com>]

On Wed, 2003-05-07 at 11:12, Paul Fulghum wrote:
> Starting with kernel version 2.5.69, I am
> encountering what appears to be increased
> interrupt latency or spikes in interrupt latency.
> ...
> I see this on 2 different machines
> (one SMP server and one laptop).
> ...
> If I can get time, I'll try and hook up a scope
> to measure the latencies precisely. I want to
> check to see if this is a known problems before doing so.

Here are some results with a scope hooked to
the hardware while running tests with a regular
interrupt pattern:

2.4.20-8 (redhat)
Latency 20-30usec
Spikes to 80usec

2.5.68
Latency 20-30usec
Spikes to 100usec

2.5.69
Latency 100-110usec (5x increase)
Spikes from 5-10 milliseconds

This is all on a PCI adapter not sharing interrupts
on a dual Pentium II-400 Netserver LC3.

Any ideas what happened?

-- 
Paul Fulghum, paulkf@microgate.com
Microgate Corporation, http://www.microgate.com