From: Stefan Hajnoczi <stefanha@redhat.com>
To: qemu-devel@nongnu.org
Cc: Peter Maydell <peter.maydell@linaro.org>,
Eduardo Habkost <ehabkost@redhat.com>,
qemu-block@nongnu.org, Markus Armbruster <armbru@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Cleber Rosa <crosa@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: [PULL 03/11] trace: recommend "log" backend for getting started with tracing
Date: Mon, 1 Feb 2021 15:46:55 +0000 [thread overview]
Message-ID: <20210201154703.180022-4-stefanha@redhat.com> (raw)
In-Reply-To: <20210201154703.180022-1-stefanha@redhat.com>
The "simple" backend is actually more complicated to use than the "log"
backend. Update the quickstart documentation to feature the "log"
backend instead of the "simple" backend.
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20201216160923.722894-4-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
docs/devel/tracing.rst | 35 ++++++++++++++++++-----------------
1 file changed, 18 insertions(+), 17 deletions(-)
diff --git a/docs/devel/tracing.rst b/docs/devel/tracing.rst
index f7e589f67c..4ebf8e38ea 100644
--- a/docs/devel/tracing.rst
+++ b/docs/devel/tracing.rst
@@ -11,22 +11,22 @@ for debugging, profiling, and observing execution.
Quickstart
==========
-1. Build with the 'simple' trace backend::
+Enable tracing of ``memory_region_ops_read`` and ``memory_region_ops_write``
+events::
- ./configure --enable-trace-backends=simple
- make
+ $ qemu --trace "memory_region_ops_*" ...
+ ...
+ 719585@1608130130.441188:memory_region_ops_read cpu 0 mr 0x562fdfbb3820 addr 0x3cc value 0x67 size 1
+ 719585@1608130130.441190:memory_region_ops_write cpu 0 mr 0x562fdfbd2f00 addr 0x3d4 value 0x70e size 2
-2. Create a file with the events you want to trace::
+This output comes from the "log" trace backend that is enabled by default when
+``./configure --enable-trace-backends=BACKENDS`` was not explicitly specified.
- echo memory_region_ops_read >/tmp/events
+More than one trace event pattern can be specified by providing a file
+instead::
-3. Run the virtual machine to produce a trace file::
-
- qemu --trace events=/tmp/events ... # your normal QEMU invocation
-
-4. Pretty-print the binary trace file::
-
- ./scripts/simpletrace.py trace-events-all trace-* # Override * with QEMU <pid>
+ $ echo "memory_region_ops_*" >/tmp/events
+ $ qemu --trace events=/tmp/events ...
Trace events
============
@@ -195,7 +195,7 @@ script.
The trace backends are chosen at configure time::
- ./configure --enable-trace-backends=simple
+ ./configure --enable-trace-backends=simple,dtrace
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.
@@ -227,10 +227,11 @@ uses DPRINTF().
Simpletrace
-----------
-The "simple" backend supports common use cases and comes as part of the QEMU
-source tree. It may not be as powerful as platform-specific or third-party
-trace backends but it is portable. This is the recommended trace backend
-unless you have specific needs for more advanced backends.
+The "simple" backend writes binary trace logs to a file from a thread, making
+it lower overhead than the "log" backend. A Python API is available for writing
+offline trace file analysis scripts. It may not be as powerful as
+platform-specific or third-party trace backends but it is portable and has no
+special library dependencies.
Monitor commands
~~~~~~~~~~~~~~~~
--
2.29.2
next prev parent reply other threads:[~2021-02-01 15:52 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-01 15:46 [PULL 00/11] Tracing patches Stefan Hajnoczi
2021-02-01 15:46 ` [PULL 01/11] trace: fix simpletrace doc mismerge Stefan Hajnoczi
2021-02-01 15:46 ` [PULL 02/11] tracing: convert documentation to rST Stefan Hajnoczi
2021-02-01 15:46 ` Stefan Hajnoczi [this message]
2021-02-01 15:46 ` [PULL 04/11] tracetool: fix "PRI" macro decoding Stefan Hajnoczi
2021-02-01 15:46 ` [PULL 05/11] tracetool: also strip %l and %ll from systemtap format strings Stefan Hajnoczi
2021-02-01 15:46 ` [PULL 06/11] trace: add meson custom_target() depend_files for tracetool Stefan Hajnoczi
2021-02-01 15:46 ` [PULL 07/11] error: rename error_with_timestamp to message_with_timestamp Stefan Hajnoczi
2021-02-01 15:47 ` [PULL 08/11] trace: make the 'log' backend timestamp configurable Stefan Hajnoczi
2021-02-01 15:47 ` [PULL 09/11] simpletrace: build() missing 2 required positional arguments Stefan Hajnoczi
2021-02-01 15:47 ` [PULL 10/11] trace: document how to specify multiple --trace patterns Stefan Hajnoczi
2021-02-01 16:05 ` BALATON Zoltan
2021-02-01 16:13 ` Kevin Wolf
2021-02-01 16:27 ` Philippe Mathieu-Daudé
2021-02-01 16:29 ` BALATON Zoltan
2021-02-01 16:54 ` Kevin Wolf
2021-02-01 17:25 ` Paolo Bonzini
2021-02-01 17:39 ` BALATON Zoltan
2021-02-02 12:41 ` Markus Armbruster
2021-02-02 13:03 ` BALATON Zoltan
2021-02-02 13:12 ` Paolo Bonzini
2021-02-01 17:46 ` Daniel P. Berrangé
2021-02-01 18:13 ` BALATON Zoltan
2021-02-02 16:47 ` Stefan Hajnoczi
2021-02-01 15:47 ` [PULL 11/11] trace: update docs with meson build information Stefan Hajnoczi
2021-02-02 11:24 ` [PULL 00/11] Tracing patches Peter Maydell
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