vlog: Move log level definitions from source code to user documentation.

Users should be able to find out what a log level means without reading
source code comments, so this seems like a better place for it.

Reported-by: David Tsai <dtsai@nicira.com>

1 files changed, 30 insertions, 1 deletions

diff --git a/utilities/ovs-appctl.8.in b/utilities/ovs-appctl.8.in
index a3688ac55..51085980b 100644
--- a/utilities/ovs-appctl.8.in
+++ b/utilities/ovs-appctl.8.in
@@ -55,9 +55,38 @@ as if it had been specified directly as the target.
 The default target is \fBovs\-vswitchd\fR.
 .
 .SH LOGGING COMMANDS
+.
+.PP
+Open vSwitch has several log levels.  The highest-severity log level
+is:
+.
+.IP "\fBOFF\fR"
+No message is ever logged at this level, so setting a logging
+facility's log level to \fBOFF\fR disables logging to that facility.
+.
+.PP
+The following log levels, in order of descending severity, are enabled
+by default:
+.
+.IP "\fBEMER\f"
+A major failure forced a process to abort.
+.IP "\fBERR\fR"
+A high-level operation or a subsystem failed.  Attention is
+warranted.
+.IP "\fBWARN\fR"
+A low-level operation failed, but higher-level subsystems may be able
+to recover.
+.IP "\fBINFO\fR"
+Information that may be useful in retrospect when investigating
+a problem.
+.IP "\fBDBG\fR"
+Information useful only to someone with intricate knowledge of the
+system, or that would commonly cause too-voluminous log output.  Log
+messages at this level are not logged by default.
+.
+.PP
 Every Open vSwitch daemon supports the following commands for
 examining and adjusting log levels.
-.
 .IP "\fBvlog/list\fR"
 Lists the known logging modules and their current levels.
 .