Re: [announce] [patch] limiting IRQ load, irq-rewrite-2.4.11-B5

Jeremy Hansen
2001-10-03T20:41:47Z

I better go check my pants...

Thanks
-jeremy

On Wed, 3 Oct 2001, Linus Torvalds wrote:

> In article <Pine.LNX.4.33.0110031920410.9973-100000@localhost.localdomain>,
> Ingo Molnar <mingo@elte.hu> wrote:
> >
> >well, just tested my RAID testsystem as well. I have not tested heavy
> >IO-related IRQ load with the patch before (so it was not tuned for that
> >test in any way), but did so now: an IO test running on 12 disks, (5 IO
> >interfaces: 3 SCSI cards and 2 IDE interfaces) producing 150 MB/sec block
> >IO load and a fair number of SCSI and IDE interrupts, did not trigger the
> >overload code.
>
> Now test it again with the disk interrupt being shared with the network
> card.
>
> Doesn't happen? It sure does. It happens more often especially on
> slightly lower-end machines (on laptops it's downright disgusting how
> often _every_ single PCI device ends up sharing the same interrupt).
>
> And as the lower-end machines are the ones that probably can be forced
> to trigger the whole thing more often, this is a real issue.
>
> And on my "high-end" machine, I actually have USB and ethernet on the
> same interrupt. It would be kind of nasty if heavy network traffic
> makes my camera stop working...
>
> The fact is, there is never any good reason for limiting "trusted"
> interrupts, ie anything that is internal to the box. Things like disks,
> graphics controllers etc.
>
> Which is why I like the NAPI approach. If somebody overloads my network
> card, my USB camera doesn't stop working.
>
> I don't disagree with your patch as a last resort when all else fails,
> but I _do_ disagree with it as a network load limiter.
>
> Linus
> -
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