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Re: [Qemu-devel] [PATCH v6 11/20] trace: emit name <-> ID mapping in sim
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH v6 11/20] trace: emit name <-> ID mapping in simpletrace header |
Date: |
Wed, 5 Oct 2016 15:09:47 +0100 |
User-agent: |
Mutt/1.7.0 (2016-08-17) |
On Tue, Oct 04, 2016 at 02:35:50PM +0100, Daniel P. Berrange wrote:
> Currently simpletrace assumes that events are given IDs
> starting from 0, based on the order in which they appear
> in the trace-events file, with no gaps. When the
> trace-events file is split up, this assumption becomes
> problematic.
>
> To deal with this, extend the simpletrace format so that
> it outputs a table of event name <-> ID mappings. That
> will allow QEMU to assign arbitrary IDs to events without
> breaking simpletrace parsing.
>
> The v3 simple trace format was
>
> FILE HEADER
> EVENT TRACE RECORD 0
> EVENT TRACE RECORD 1
> ...
> EVENT TRACE RECORD N
>
> The v4 simple trace format is now
>
> FILE HEADER
> EVENT MAPPING RECORD 0
> EVENT MAPPING RECORD 1
> ...
> EVENT MAPPING RECORD M
> EVENT TRACE RECORD RECORD 0
> EVENT TRACE RECORD RECORD 1
> ...
> EVENT TRACE RECORD N
>
> Although this shows all the mapping records being emitted
> upfront, this is not required by the format. While the main
> simpletrace backend will emit all mappings at startup,
> the systemtap simpletrace.stp script will emit the mappings
> at first use. eg
>
> FILE HEADER
> ...
> EVENT MAPPING RECORD 0
> EVENT TRACE RECORD RECORD 0
> EVENT TRACE RECORD RECORD 1
> EVENT MAPPING RECORD 1
> EVENT TRACE RECORD RECORD 2
> ...
> EVENT TRACE RECORD N
>
> This is more space efficient given that most trace records
> only include a subset of events.
>
> In modifying the systemtap simpletrace code, a 'begin' probe
> was added to emit the trace event header, so you no longer
> need to add '--no-header' when running simpletrace.py for
> systemtap generated trace files.
>
> Signed-off-by: Daniel P. Berrange <address@hidden>
> ---
> scripts/simpletrace.py | 50
> ++++++++++++++++++++--------
> scripts/tracetool/format/simpletrace_stap.py | 24 +++++++++++--
> trace/simple.c | 33 ++++++++++++++++--
> 3 files changed, 89 insertions(+), 18 deletions(-)
Reviewed-by: Stefan Hajnoczi <address@hidden>
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- [Qemu-devel] [PATCH v6 06/20] trace: remove global 'uint16 dstate[]' array, (continued)
- [Qemu-devel] [PATCH v6 06/20] trace: remove global 'uint16 dstate[]' array, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 07/20] trace: remove duplicate control.h includes in generated-tracers.h, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 08/20] trace: break circular dependency in event-internal.h, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 09/20] trace: give each trace event a named TraceEvent struct, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 10/20] trace: remove the TraceEventID and TraceEventVCPUID enums, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 12/20] trace: don't abort qemu if ftrace can't be initialized, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 13/20] trace: provide mechanism for registering trace events, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 11/20] trace: emit name <-> ID mapping in simpletrace header, Daniel P. Berrange, 2016/10/04
- Re: [Qemu-devel] [PATCH v6 11/20] trace: emit name <-> ID mapping in simpletrace header,
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH v6 14/20] trace: dynamically allocate trace_dstate in CPUState, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 15/20] trace: dynamically allocate event IDs at runtime, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 16/20] trace: get rid of generated-events.h/generated-events.c, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 17/20] trace: rename _read_events to read_events, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 19/20] trace: pass trace-events to tracetool as a positional param, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 18/20] trace: push reading of events up a level to tracetool main, Daniel P. Berrange, 2016/10/04
- [Qemu-devel] [PATCH v6 20/20] trace: introduce a formal group name for trace events, Daniel P. Berrange, 2016/10/04
- Re: [Qemu-devel] [PATCH v6 00/20] Refactor trace to allow modular build, Stefan Hajnoczi, 2016/10/05