Re: Van Jacobson's net channels and real-time

["linux-os \(Dick Johnson\)" <linux-os@analogic.com>]

On Mon, 24 Apr 2006, Auke Kok wrote:

> Ingo Oeser wrote:
>> On Saturday, 22. April 2006 15:49, Jörn Engel wrote:
>>> That was another main point, yes.  And the endpoints should be as
>>> little burden on the bottlenecks as possible.  One bottleneck is the
>>> receive interrupt, which shouldn't wait for cachelines from other cpus
>>> too much.
>>
>> Thats right. This will be made a non issue with early demuxing
>> on the NIC and MSI (or was it MSI-X?) which will select
>> the right CPU based on hardware channels.
>
> MSI-X. with MSI you still have only one cpu handling all MSI interrupts and
> that doesn't look any different than ordinary interrupts. MSI-X will allow
> much better interrupt handling across several cpu's.
>
> Auke
> -

Message signaled interrupts are just a kudge to save a trace on a
PC board (read make junk cheaper still). They are not faster and
may even be slower. They will not be the salvation of any interrupt
latency problems. The solutions for increasing networking speed,
where the bit-rate on the wire gets close to the bit-rate on the
bus, is to put more and more of the networking code inside the
network board. The CPU get interrupted after most things (like
network handshakes) are complete.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.4 on an i686 machine (5592.89 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_


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