lkml.org 
[lkml]   [2000]   [Sep]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: zero-copy TCP
Jes Sorensen wrote:
> You can't DMA directly from a file cache page unless you have a
> network card that does scatter/gather DMA and surprise surprise,
> 80-90% of the cards on the market don't support this. Besides that you
> need to do copy-on-write if you want to be able to do zero copy on
> write() from user space, marking data copy on write is *expensive* on
> x86 SMP boxes since you have to modify the tlb on all
> processors. On top of that you have to look at the packet size, for
> small packets a copy is often a lot cheaper than modifying the page
> tables, even on UP systems so you need a copy/break scheme here.

I just thought I'd mention that you can do zero copy TCP in and out
*without* any page marking schemes. All you need is a network card with
quite a lot of RAM and some intelligence. An Alteon could do it, with
extra RAM or an impressively underloaded network.

(for example) http://www.digital.com/info/DTJS05/

-- Jamie
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:38    [W:0.236 / U:0.180 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site