Re: zero-copy networking & a performance drop

From: Bernd Eckenfels (
Date: Thu Jun 27 2002 - 16:08:40 EST

In article <> you wrote:
> Previous tests have show that we can transmit IP packets easily at around
> 1.4 Gbit, but we can only receive at about 0.9 Gbit. We suspect there is a
> memory copy somewhere either in the quadrics IP driver (covered by an NDA,
> sorry), or in the IP stack after netif_rx() is called. I've looked at the
> driver, and, upon a (good) cursory inspection, it looks good.

You have to sign a NDA for a hardware which bahaves slower than expected and
then u seek help in the open community? I would ask you to bother the
manufacturer, so they know about this problem and solve it. After all, if
you have to pay for it you should actually USE their service.

AFAIK only a few methods like sendfile support zero copy ip.

But on the other hand, if the card works by memory sharing perhaps TCP/IP is
simply the wrong api to speak to that device?

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