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Re: [PATCH 1/2] trace: document how to specify multiple --trace patterns

From: BALATON Zoltan
Subject: Re: [PATCH 1/2] trace: document how to specify multiple --trace patterns
Date: Tue, 12 Jan 2021 21:44:03 +0100 (CET)

On Tue, 12 Jan 2021, Stefan Hajnoczi wrote:
It is possible to repeat the --trace option to specify multiple
patterns. This may be preferrable to users who do not want to create a
file with a list of patterns.

Suggested-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
docs/devel/tracing.rst | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/docs/devel/tracing.rst b/docs/devel/tracing.rst
index 4ebf8e38ea..8777c19d14 100644
--- a/docs/devel/tracing.rst
+++ b/docs/devel/tracing.rst
@@ -22,10 +22,15 @@ events::
This output comes from the "log" trace backend that is enabled by default when
``./configure --enable-trace-backends=BACKENDS`` was not explicitly specified.

-More than one trace event pattern can be specified by providing a file
+Multiple patterns can be specified by repeating the ``--trace`` option::
+    $ qemu --trace "kvm_*" --trace "virtio_*" ...

QEMU options are single dash with double dash accepted for compatibility but help and other docs have single dash so these (and below) should be -trace. (Also a bit less typing for otherwise already way too long command lines.)


+When patterns are used frequently it is more convenient to store them in a
+file to avoid long command-line options::

    $ echo "memory_region_ops_*" >/tmp/events
+    $ echo "kvm_*" >>/tmp/events
    $ qemu --trace events=/tmp/events ...

Trace events

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