trace: document '-' syntax for disabling events
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
diff --git a/docs/tracing.txt b/docs/tracing.txt
index c541133..7901409 100644
--- a/docs/tracing.txt
+++ b/docs/tracing.txt
@@ -139,6 +139,10 @@
be enabled using:
trace-event virtio_blk_* on
+If a line in the "-trace events=<file>" file begins with a '-', the trace event
+will be disabled instead of enabled. This is useful when a wildcard was used
+to enable an entire family of events but one noisy event needs to be disabled.
+
== Trace backends ==
The "tracetool" script automates tedious trace event code generation and also
