svn commit: r241955 - head

[Andre Oppermann]

Author: andre
Date: Tue Oct 23 16:33:43 2012
New Revision: 241955
URL: http://svn.freebsd.org/changeset/base/241955

Log:
  Note the removal of the ZERO_COPY_SOCKETS kernel option in r241931
  and provide a proper explanation.

Modified:
  head/UPDATING

Modified: head/UPDATING
==============================================================================
--- head/UPDATING	Tue Oct 23 16:12:17 2012	(r241954)
+++ head/UPDATING	Tue Oct 23 16:33:43 2012	(r241955)
@@ -25,6 +25,17 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 10
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
 20121023:
+	The ZERO_COPY_SOCKET kernel option has been removed and
+	split into SOCKET_SEND_COW and SOCKET_RECV_PFLIP.
+	NB: SOCKET_SEND_COW uses the VM page based copy-on-write
+	mechanism which is not safe and may result in kernel crashes.
+	NB: The SOCKET_RECV_PFLIP mechanism is useless as no current
+	driver supports disposeable external page sized mbuf storage.
+	Proper replacements for both zero-copy mechanisms are under
+	consideration and will eventually lead to complete removal
+	of the two kernel options.
+
+20121023:
 	The IPv4 network stack has been converted to network byte
 	order. The following modules need to be recompiled together
 	with kernel: carp(4), divert(4), gif(4), siftr(4), gre(4),