docs/tracing.txt: Update documentation of default backend

In commit baf86d6b3c we switched the default trace backend from "nop"
to "log". Update the documentation to match.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1478276837-31780-1-git-send-email-peter.maydell@linaro.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Peter Maydell 2016-11-04 16:27:17 +00:00 committed by Stefan Hajnoczi
parent 207faf24c5
commit 3b0fc80dd8
1 changed files with 5 additions and 2 deletions

View File

@ -150,13 +150,16 @@ The trace backends are chosen at configure time:
For a list of supported trace backends, try ./configure --help or see below.
If multiple backends are enabled, the trace is sent to them all.
If no backends are explicitly selected, configure will default to the
"log" backend.
The following subsections describe the supported trace backends.
=== Nop ===
The "nop" backend generates empty trace event functions so that the compiler
can optimize out trace events completely. This is the default and imposes no
performance penalty.
can optimize out trace events completely. This imposes no performance
penalty.
Note that regardless of the selected trace backend, events with the "disable"
property will be generated with the "nop" backend.