Document background noise of RX packets from bridges (RHBZ#647987).

[virt-top.git] / virt-top / virt-top.pod

diff --git a/virt-top/virt-top.pod b/virt-top/virt-top.pod
index 283185d..4d7df4e 100755 (executable)
--- a/virt-top/virt-top.pod
+++ b/virt-top/virt-top.pod
@@ -69,7 +69,7 @@ is to run continuously.
 
 Set the sort order to one of:
 B<cpu> (sort by %CPU used),
-B<mem> (sort by memory used),
+B<mem> (sort by total memory),
 B<time> (sort by total time),
 B<id> (sort by domain ID),
 B<name> (sort by domain name),
@@ -252,7 +252,8 @@ Sort by %CPU.
 
 =item I<M>
 
-Sort by memory.
+Sort by total memory.  Note that this shows the total memory
+allocated to the guest, not the memory being used.
 
 =item I<T>
 
@@ -364,20 +365,32 @@ init file.
 
 =back
 
-
 Note that in the current implementation, options specified in
 the init file override options specified on the command line.
 This is a bug and this behaviour may change in the future.
 
+=head1 NOTES
+
+=head2 NETWORK RX BYTES AND PACKETS
+
+Libvirt/virt-top has no way to know that a packet transmitted to a
+guest was received (eg. if the guest is not listening).  In the
+network RX stats, virt-top reports the packets transmitted to the
+guest, on the basis that the guest might receive them.
+
+In particular this includes broadcast packets.  Because of the way
+that Linux bridges work, if the guest is connected to a bridge, it
+will probably see a steady "background noise" of RX packets even when
+the network interface is idle or down.  These are caused by STP
+packets generated by the bridge.
+
 =head1 SEE ALSO
 
 L<top(1)>,
 L<virsh(1)>,
-L<xm(1)>,
-L<xentop(1)>,
 L<http://www.libvirt.org/ocaml/>,
 L<http://www.libvirt.org/>,
-L<http://et.redhat.com/~rjones/>,
+L<http://people.redhat.com/~rjones/>,
 L<http://caml.inria.fr/>
 
 =head1 AUTHORS
@@ -386,7 +399,7 @@ Richard W.M. Jones <rjones @ redhat . com>
 
 =head1 COPYRIGHT
 
-(C) Copyright 2007 Red Hat Inc., Richard W.M. Jones
+(C) Copyright 2007-2011 Red Hat Inc., Richard W.M. Jones
 http://libvirt.org/
 
 This program is free software; you can redistribute it and/or modify