> I know that all USB host controllers interrupt *really* frequently.
> (1000Hz.) This is a flaw in the way those interfaces were designed.
> Its true when *any* device is plugged into the port, I believe.
Maybe the usb host controllers access system memory that
frequently, but they don't interrupt 1000 times a second
(unless there is an usb device plugged in that really needs
to send 1000 interrupts per second). Check with intrstat.
E.g. when I constantly move an usb connected logitech mouse,
I see a max of 50 interrupts / second on ohci#0. (And no
interrupts on ehci#0, and ~125 interrupts on ehci#1 which
happens to have a shared interrupt vector with an nvidia
video card)
device | cpu0 %tim cpu1 %tim
-------------+------------------------------
ahci#0 | 0 0,0 125 0,0
ata#0 | 0 0,0 0 0,0
ehci#0 | 10 0,1 0 0,0
ehci#1 | 0 0,0 125 0,0
hci1394#0 | 0 0,0 0 0,0
nv_sata#0 | 0 0,0 0 0,0
nv_sata#1 | 0 0,0 0 0,0
nvidia#0 | 0 0,0 125 0,7
ohci#0 | 0 0,0 50 0,1
ohci#1 | 0 0,0 0 0,0
ohci#2 | 0 0,0 0 0,0
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