[ltt-dev] LTT deamon process scheduling

[Mathieu Desnoyers]

* Ali Günhan Akyürek (aliakyurek at gmail.com) wrote:
> Hi,
> 
> I have a little question. Suppose my application enters an infinite loop or
> hanged up for a while and it's the highest priority application in the
> system and does not release CPU.
> If LTT deamon is not scheduled at these moments, what will be the result of
> the trace, loss of events?

Yes, by default (the "discard" mode), for the kernel LTTng, events will
be dropped when the buffer is full (in this case caused by lttd never
running). You can also setup LTTng to use the "flight recorder" (also
called "overwrite") mode, which will overwrite the oldest information in
the circular buffer (thus not requiring the trace data to be consumed by
lttd while tracing is active).

> 
> So, is there rule that LTT deamon must run for ex. in each 10ms.?

Not really. It depends on the amount of data it has to move, the speed
of your I/O device, etc.

Mathieu

> 
> Thanks in advance.
> Ali

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-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com