Re: [PATCH v4 0/2] trace: Add a trace backend for the recorder library

[Stefan Hajnoczi]

On Thu, Jul 23, 2020 at 03:29:01PM +0200, Christophe de Dinechin wrote:
> The recorder library implements low-cost always-on tracing, with three
> usage models:
> 
> 1. Flight recorder: Dump information on recent events in case of crash
> 2. Tracing: Individual traces can be enabled using environment variables
> 3. Real-time graphing / control, using the recorder_scope application
> 
> This short series introduces a new "recorder" back-end which connects
> to the recorder. Traces using the recorder are intentionally "always on",
> because the recorder library is primarily designed to record
> information for later playback in case of crash, tracing being only a
> secondary capability.
> 
> An example is given of how the recorder can also be used separately
> from generated traces. The example uses locking, which can make sense
> for both post-mortem and real-time graphing.
> 
> Changes in v3:
> * Address coding style issues (C++ comments, wrong include, etc)
> * Fix args type for HMP command (for now, still a single command)
> * Add basic help for HMP command
> * Use pkg-config for recorder information. This requires recorder
>   1.0.10 or later.
> 
> Changes in v4:
> * Rebased on current master
> * Fix GPL v2-only license
> * Remove confusing #ifdef around #include "trace/recorder.h"
> * Added myself as a reviewer for trace subsystem
> 
> Later patches wil address larger topics that were discussed that
> would impact other tracing mechanisms, as well as GitHub / GitLab
> build tests.

Thanks, I will take a look next week. QEMU is in freeze at the moment
and new features are not being added until QEMU 5.1 is released.

Stefan

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