- New sysctl variable: net.inet.ip.dummynet.io_fast

  If it is set to zero value (default) dummynet module will try to emulate
  real link as close as possible (bandwidth & latency): packet will not leave
  pipe faster than it should be on real link with given bandwidth.
  (This is original behaviour of dummynet which was altered in previous commit)
  If it is set to non-zero value only bandwidth is enforced: packet's latency
  can be lower comparing to real link with given bandwidth.

- Document recently introduced dummynet(4) sysctl variables.

Requested by:	luigi, julian
MFC after:	3 month

1 files changed, 19 insertions, 1 deletions

diff --git a/sbin/ipfw/ipfw.8 b/sbin/ipfw/ipfw.8
index 078d010..52d2d3d 100644
--- a/sbin/ipfw/ipfw.8
+++ b/sbin/ipfw/ipfw.8
@@ -1,7 +1,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd October 19, 2007
+.Dd November 17, 2007
 .Dt IPFW 8
 .Os
 .Sh NAME
@@ -1756,6 +1756,16 @@ Depending on local policies, a flow can contain packets for a single
 TCP connection, or from/to a given host, or entire subnet, or a
 protocol type, etc.
 .Pp
+There are two modes of dummynet operation: normal and fast.
+Normal mode tries to emulate real link: dummynet scheduler ensures packet will
+not leave pipe faster than it would be on real link with given bandwidth.
+Fast mode allows certain packets to bypass dummynet scheduler (if packet flow
+does not exceed pipe's bandwidth). Thus fast mode requires less cpu cycles
+per packet (in average) but packet latency can be significantly lower comparing
+to real link with same bandwidth. Default is normal mode, fast mode can be
+enabled by setting net.inet.ip.dummynet.io_fast sysctl(8) variable to non-zero
+value.
+.Pp
 Packets belonging to the same flow are then passed to either of two
 different objects, which implement the traffic regulation:
 .Bl -hang -offset XXXX
@@ -2120,6 +2130,14 @@ Default size of the hash table used for dynamic pipes/queues.
 This value is used when no
 .Cm buckets
 option is specified when configuring a pipe/queue.
+.It Em net.inet.ip.dummynet.io_fast : No 0
+If set to non-zero value enables "fast" mode of dummynet operation (see above).
+.It Em net.inet.ip.dummynet.io_pkt
+Number of packets passed to by dummynet.
+.It Em net.inet.ip.dummynet.io_pkt_drop
+Number of packets dropped by dummynet.
+.It Em net.inet.ip.dummynet.io_pkt_fast
+Number of packets bypassed dummynet scheduler.
 .It Em net.inet.ip.dummynet.max_chain_len : No 16
 Target value for the maximum number of pipes/queues in a hash bucket.
 The product