FreeBSD's new zero-copy networking

From: Dan Kegel (dank@alumni.caltech.edu)
Date: Mon Sep 18 2000 - 09:52:22 EST


http://www.kegel.com/c10k.html#zerocopy now links to
http://people.freebsd.org/~ken/zero_copy/ which describes
some patches for FreeBSD which add support for zero-copy
networking from user space.

Where they're headed is:
  When transferring one or more pages via a page-alligned
  buffer and normal read() or write(), VM tricks will be
  used to avoid copying the data. If you touch the page
  before the transfer is done, copy-on-write semantics
  will be used to avoid screwing up the transfer.
  Best to use aio_write etc. so you know when the transfer
  is done, so you can reuse the buffer.

They've gotten 960 megabits/sec out of a gigabit Ethernet card
with this. Not stable yet.

Pretty nifty...
- Dan
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