[ltt-dev] Is 'early boot' feature working?

[Mathieu Desnoyers]

* Yang Liu (fred.yang.liu at gmail.com) wrote:
> Hello, all,
> I think there is a feature named 'early boot' and want to know if it is
> there.

LTTng depends on RCU, page allocation and cycle counter synchronization.
Starting after these are setup at early boot should be OK.

> If it is there, how to use it?

If you need to start tracing very early, I recommend creating a new
kernel builtin module which reads the kernel command line arguments
and enables early tracing when some lttng_early_trace=1 argument is
encountered.

> How early it could approximately be since epoch?

See answer above for dependencies. Time will vary depending on where
these pieces of infrastructure (rcu, page allocation and cycle counter)
are enabled.

Mathieu

> 
> Best regards,
> Fred

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Mathieu Desnoyers
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