irq and softirq handler measurement

Hello,

I'd like to propose a modification of the linux kernel, which enables IRQ and SOFTIRQ handler measurement. The patch currently covers only i386 architecture, but could be extented to other architectures as well.

I tried to measure time spent in mentioned hendler functions, by summarizing times spent in every part of their execution. This means that a new nested interrupt ends one part of time measurement for the first (previously running) IRQ or SOFTIRQ and starts a new part of time measurement for the second (newly started) IRQ.
It may not be the most optimal solution (suggestions are most welcome), but it's been helpfull to me. Measurements may be usefull, for developing new drivers or if you are optimising your system.

The linux (2.6.0-test11) patch has not been pasted at the end of the following usage description, because it is quite long, so here is the URL:

        http://friends.s5.net/pogacnik/patch-2.6.0-test11-usage-0.1.

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Usage description:

1. Measure IRQ handlers

This option enables measurement of time spent in each IRQ handler. Measured data is being displayed through the /proc/interrupts file. The CPU usage mean value for each IRQ handler and the maximum continuous time spent in each IRQ handler are being calculated for the time elapsed between two subsequent reads of the /proc/interrupts file.

2. Measure SOFTIRQ handlers
This option enables measurement of time spent in each SOFTIRQ handler. Measurement includes every tasklet, that is being registered for this measure through the tasklet_register() function. The tasklet_init() calls register tasklets automaticaly.
Measured data is being displayed through the /proc/softirqs file. The CPU usage mean value for each SOFTIRQ handler and the maximum continuous time spent in each SOFTIRQ handler are being calculated for the time elapsed between two subsequent reads of the /proc/softirqs file. Additionally the number of invocations for each SOFTIRQ handler (as well as for each tasklet) is being displayed through the /proc/softirqs file.

3. The patch
This linux patch allows you to configure the kernel for compilation without any of the above options.
First read of interrupts (or softirqs) file can not calculate CPU usage correctly, because there is no previous time reference.
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kind regards to all Linux developers, Samo Pogacnik