[LAU] midi triggering delay

[James Cameron]

On Tue, Sep 08, 2009 at 07:17:30PM -1000, david wrote:
> USB not sharing interrupts with anything?

Andy's original post contained /proc/interrupts which showed some
sharing was happening.  Here's a cut:

 16:     380396     233180   IO-APIC-fasteoi   uhci_hcd:usb4, yenta
 17:     829711     532117   IO-APIC-fasteoi   uhci_hcd:usb5, ohci1394, HDA Intel
 18:          0          0   IO-APIC-fasteoi   mmc0
 19:          2          0   IO-APIC-fasteoi   ehci_hcd:usb6
 20:         18         17   IO-APIC-fasteoi   uhci_hcd:usb1
 21:          0          0   IO-APIC-fasteoi   uhci_hcd:usb2
 22:     305246     302929   IO-APIC-fasteoi   ehci_hcd:usb3

Sharing interrupts adds a tiny delay to interrupt handling; if this has
truly become significant, there's a design issue somewhere else.

(Shared interrupts with modern kernels are not a huge problem, since the
drivers check to see if the interrupt they have is legitimate before the
kernel chains on to the next driver.  It's the waste of that additional
check that people want to avoid.)

-- 
James Cameron
http://quozl.linux.org.au/