Re: zero-copy TCP

From: Jes Sorensen (
Date: Mon Sep 04 2000 - 09:54:40 EST

>>>>> "Ingo" == Ingo Molnar <> writes:

Ingo> i believe such zero-copy send should only be allowed for drivers
Ingo> which can guarantee correct checksums. (ie. cards which do
Ingo> Tx-checksums) The other drivers will still copy. I dont think
Ingo> this is a problem - the number of cards that can do
Ingo> scatter-gather DMA but cannot do TX-checksumming is rather
Ingo> low. (i only know about the Tulip.) All modern cards do
Ingo> TX-checksumming and scatter-gather DMA.

The Essential RoadRunner HIPPI card has the same 'problem'/. My main
interest in getting scatter/gather working for that one is for receive
since I want to avoid having to allocate 64KB contigous receive
buffers. Instead I'd like to throw it a pile of pages and then stick
the pages actually used by a packet (it's often less than 64KB) into a
kiobuf and build an skb from that.

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