linux-kernel - Re: [RFC] split NAPI from network device.

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Date:	Thu, 22 Feb 2007 10:24:31 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	David Miller <davem@...emloft.net>
Cc:	shemminger@...l.org, netdev@...r.kernel.org, ebs@...home.net,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] split NAPI from network device.

> Actually, Ben did you determine if this scheme works for your device
> which has a single interrupt source yet multiple queues?  There is one
> driver that, during the conversion, I noticed has a similar issue.
> One driver, netxen, has multiple channels, so it just passes in
> "bugdet / NUM_CHANNELS" as the quota so that one channel could not
> starve the others.

The device has a single interrupt though that interrupt at least can
tell you which queues need servicing. It can't mask the interrupt per
queue though, which is the main issue.

So while I think this scheme would work (the driver, ibm_emac, currently
uses a fake net_device and that sort-of works, budget is set a CONFIG_*
time though, I'm sure that can/needs to be improved), I've been
wondering all along if I could do something smarter by doing some
interrupt soft-disabling instead, though I have to get my head around
properly kicking softirqs from task context (if I need to re-trigger
from a enable_*() call occuring at task context).

I'm travelling at the moment, so I won't be able to have a serious look
for a little while though.

Cheers,
Ben.

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