Re: [PATCH] new irq tracer

[Peter Zijlstra]

On Wed, 2009-02-18 at 14:53 -0500, Jason Baron wrote:
> hi,
> 
> Using a copule of tracepoints i've implemented an 'irq tracer' which has
> the following column format:
> 
> [time][irq][action][handled][cpu][length]
> 
> for example on my system:
> 
> [ 1038.927248381]     28     eth0      1        3     0.000002745
> [ 1038.927544688]     28     eth0      1        3     0.000002520
> [ 1038.927593609]     28     eth0      1        3     0.000002509
> [ 1038.974087675]     29     ahci      1        1     0.000013135
> [ 1038.974288475]     29     ahci      1        1     0.000005542
> [ 1038.974414324]     29     ahci      1        1     0.000007953
> 
> I think this patch is useful in understanding irq system behavior, and
> for tracking down irq driver handlers that are firing too often or
> spending too much time handling an irq. This approach could be extended
> to the timer irq and for softirqs...

The function graph tracer can already do this, it has a special section
to recognize irq entry function, and already measures time spend.

I guess with Steve's new triggers (probes or whatever they ended up
being called) you could limit it to just IRQ entry points.



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/