[dm-devel] Re: PROBLEM: powertop reports 8000 spurious interrupts/s from USB disk

[David Brownell <david-b pacbell net>]

I've never observed such absurd IRQ rates myself.

Now, "8000" is an interesting number since there are 1000 USB frames
per second, and 8 microframes per frame ... so you might be able to
make this better by "modprobe ehci-hcd log2_irq_thresh=3" to change
the IRQ latency from 1 microframe to 8.


On Monday 05 May 2008, Alan Stern wrote:
> One thing you can do is to mount a debugfs filesystem, and under it go
> to the EHCI directory corresponding to the controller your drive is 
> plugged into.  The contents of the "registers" and "async" files would 
> be interesting -- particularly if you get them while the disk is idle.
> 
> You might even try looking at "registers" several times in a row, since 
> its contents may change over time.

Exactly.