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[Qemu-devel] [PATCH v3 00/14] trace: Add static tracing to QEMU
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH v3 00/14] trace: Add static tracing to QEMU |
Date: |
Mon, 6 Sep 2010 16:13:57 +0100 |
This patch series adds static tracing to QEMU. It can be used to instrument
QEMU code by means of lightweight logging called trace events.
Prerna and I are now posting the entire patch series with a serious eye towards
checking we meet users' and developers' tracing needs and with the goal of
getting this functionality merged into qemu.git.
Tracing infrastructure allows debugging, performance analysis, and observation
to be performed. Right now there are ad-hoc logging calls in some source files
which require rebuilding QEMU with certain #defines and perform poorly. This
patch series introduces a single tracing infrastructure which is easy to use
and can replace ad-hoc techniques.
Two key points:
1. The trace-events file contains the set of defined trace events which can be
called from a source file. For example, trace-events has:
qemu_malloc(size_t size, void *ptr) "size %zu ptr %p"
and qemu-malloc.c uses this trace event like this:
#include "trace.h" /* needed for trace event prototype */
void *qemu_malloc(size_t size)
{
void *ptr;
if (!size && !allow_zero_malloc()) {
abort();
}
ptr = oom_check(malloc(size ? size : 1));
trace_qemu_malloc(size, ptr); /* <-- trace event */
return ptr;
}
2. The built-in 'simple' trace backend writes binary traces to
trace-<pid>. They can be pretty-printed like this:
./simpletrace.py trace-events trace-*
Although you can also try LTTng Userspace Tracer ('ust' trace backend), the
'simple' trace backend provides commands within the QEMU monitor to
enable/disable trace events at runtime. It is easy to use and should serve
as a good default trace backend.
The 'simple' trace backend's limitation is that it isn't thread-safe and can
therefore only trace correctly when the QEMU global mutex is held.
For full documentation, see:
http://repo.or.cz/w/qemu/stefanha.git/blob_plain/refs/heads/tracing_v3:/docs/tracing.txt
The git branch is here:
http://repo.or.cz/w/qemu/stefanha.git/shortlog/refs/heads/tracing_v3
Changes in v3:
* write trace files to current working directory by default
* avoid adding -lust to LIBS twice
Changes in v2:
* add 6th argument to trace record to avoid changing file format later
* add type usage documentation for trace event declarations
* switch to QemuOptsList for -trace command-line option
* use atexit() once and only once to flush the trace buffer
* keep disabled event ids in sync between tracetool and simpletrace.py
* change echo -n to printf for portability
* move #include statements to correct spot in the patch series
* fix style issues from code review
- [Qemu-devel] [PATCH v3 00/14] trace: Add static tracing to QEMU,
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH 14/14] trace: Trace entry point of balloon request handler, Stefan Hajnoczi, 2010/09/06
- [Qemu-devel] [PATCH 05/14] trace: Specify trace file name, Stefan Hajnoczi, 2010/09/06
- [Qemu-devel] [PATCH 08/14] trace: Add LTTng Userspace Tracer backend, Stefan Hajnoczi, 2010/09/06
- [Qemu-devel] [PATCH 10/14] trace: Trace qemu_malloc() and qemu_vmalloc(), Stefan Hajnoczi, 2010/09/06
- [Qemu-devel] [PATCH 06/14] trace: Add trace-file command to open/close/flush trace file, Stefan Hajnoczi, 2010/09/06
- [Qemu-devel] [PATCH 03/14] trace: Support for dynamically enabling/disabling trace events, Stefan Hajnoczi, 2010/09/06
- [Qemu-devel] [PATCH 13/14] trace: Trace port IO, Stefan Hajnoczi, 2010/09/06
- [Qemu-devel] [PATCH 04/14] trace: Support disabled events in trace-events, Stefan Hajnoczi, 2010/09/06
- [Qemu-devel] [PATCH 07/14] trace: Add trace file name command-line option, Stefan Hajnoczi, 2010/09/06
- [Qemu-devel] [PATCH 02/14] trace: Add simple built-in tracing backend, Stefan Hajnoczi, 2010/09/06