From 1f3c5a55e0dbbab20fcd23cd81689e0f6ca72669 Mon Sep 17 00:00:00 2001 From: "Richard W.M. Jones" Date: Thu, 6 Jan 2011 13:34:16 +0000 Subject: [PATCH] Document background noise of RX packets from bridges (RHBZ#647987). For more information see: https://bugzilla.redhat.com/show_bug.cgi?id=647987#c9 --- virt-top/virt-top.1 | 14 ++++++++++++++ virt-top/virt-top.pod | 15 +++++++++++++++ virt-top/virt-top.txt | 13 +++++++++++++ 3 files changed, 42 insertions(+) diff --git a/virt-top/virt-top.1 b/virt-top/virt-top.1 index 1cd5843..2665e27 100755 --- a/virt-top/virt-top.1 +++ b/virt-top/virt-top.1 @@ -437,6 +437,20 @@ init file. 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. +.SH "NOTES" +.IX Header "NOTES" +.SS "\s-1NETWORK\s0 \s-1RX\s0 \s-1BYTES\s0 \s-1AND\s0 \s-1PACKETS\s0" +.IX Subsection "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 \s-1RX\s0 stats, virt-top reports the packets transmitted to the +guest, on the basis that the guest might receive them. +.PP +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 \*(L"background noise\*(R" of \s-1RX\s0 packets even when +the network interface is idle or down. These are caused by \s-1STP\s0 +packets generated by the bridge. .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fItop\fR\|(1), diff --git a/virt-top/virt-top.pod b/virt-top/virt-top.pod index e11e814..4d7df4e 100755 --- a/virt-top/virt-top.pod +++ b/virt-top/virt-top.pod @@ -369,6 +369,21 @@ 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, diff --git a/virt-top/virt-top.txt b/virt-top/virt-top.txt index da737b8..de0681e 100644 --- a/virt-top/virt-top.txt +++ b/virt-top/virt-top.txt @@ -269,6 +269,19 @@ INIT FILE file override options specified on the command line. This is a bug and this behaviour may change in the future. +NOTES + 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. + SEE ALSO top(1), virsh(1), , , , -- 1.8.3.1