Re: [Qemu-devel] [PATCH v2 0/4] trace: add simpletrace-stap format to generate binary trace

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Sun, Jun 22, 2014 at 09:46:03PM +0800, Stefan Hajnoczi wrote:
> v2:
>  * I realized that v1 was not complete enough after feedback from Lluís and
>    Frank Ch. Eigler, so here is a v2 after all.
>  * Add Makefile target for simpletrace .stp file [Lluís]
>  * Generate SystemTap probe aliases so users can select a subset of probes to
>    enable [Frank Ch. Eigler]
>  * Delete --no-header from sys.argv[] so further command-line parsing works
> 
> SystemTap is a popular tracing solution on Fedora and RHEL.  It does not have
> its own trace file format, instead stap scripts have the freedom to output data
> in whatever format is most appropriate.
> 
> QEMU supports the simpletrace binary format for built-in tracing that comes
> with QEMU.  Since we need a format for persisting SystemTap traces and a binary
> format has performance advantages, let's output simpletrace-compatible data.
> 
> This patch adds a new stap file that is autogenerated from trace-events.  The
> following example shows how to use SystemTap and analyze the resulting trace
> file with simpletrace.py:
> 
>   $ ./configure --enable-trace-backend=dtrace ... && make
>   $ sudo stap x86_64-softmmu/qemu-system-x86_64-simpletrace.stp >trace
>   ...run QEMU in another shell...
>   ^C
>   $ scripts/simpletrace.py --no-header trace-events trace
> 
> One new concept here is the simpletrace.py --no-header option.  SystemTap
> supports flight-recorder mode where trace records are written into a ring
> buffer.  The ring buffer can be dumped at any time so it is useful to skip the
> simpletrace header check.
> 
> Stefan Hajnoczi (4):
>   trace: extract stap_escape() function for reuse
>   trace: add tracetool simpletrace_stap format
>   simpletrace: add simpletrace.py --no-header option
>   trace: install simpletrace SystemTap tapset
> 
>  Makefile.target                              | 10 +++-
>  scripts/simpletrace.py                       | 24 +++++++---
>  scripts/tracetool/format/simpletrace_stap.py | 71 ++++++++++++++++++++++++++++
>  scripts/tracetool/format/stap.py             | 11 +++--
>  4 files changed, 105 insertions(+), 11 deletions(-)
>  create mode 100644 scripts/tracetool/format/simpletrace_stap.py

Applied to my tracing-next tree:
https://github.com/stefanha/qemu/commits/tracing-next

Stefan

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