Subject: Re: 2.5.69 Interrupt Latency
From: Paul Fulghum <paulkf@microgate.com>
To: linux-kernel@vger.kernel.org
In-Reply-To: <1052323940.2360.7.camel@diemos>
References: <1052323940.2360.7.camel@diemos>
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Message-Id: <1052336482.2020.8.camel@diemos>
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Date: 07 May 2003 14:41:23 -0500
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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


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