Re: [LAU] midi triggering delay

From: andy baxter <andy@email-addr-hidden-online.co.uk>
Date: Wed Sep 09 2009 - 11:28:18 EEST

James Cameron wrote:
> 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.)
>
>
The usb port I'm using is on INT 21 (uhci_hcd:usb2), which doesn't share
with anything.

andy

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Received on Wed Sep 9 12:15:02 2009

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