Re: LTTng user-space callstacks

[Milian Wolff via lttng-dev <lttng-dev@lists.lttng.org>]

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On Freitag, 27. März 2020 14:55:08 CET Mathieu Desnoyers wrote:
> Last time I checked, the main issue with perf's handling of cases that lack
> frame pointers is that they grab a ~2-4kB worth of stack data into the
> trace, and then post-process it with libunwind. This might be OK for
> sampling use-cases, but is not something I consider appropriate for tracing
> due to considerably increased use of tracing throughput.
> 
> Has the situation changed on the perf side ?

Perf still does this. But heaptrack, of which I'm the main author, uses 
libunwind to unwind on every heap allocation and it's plenty fast. Obviously 
the impact is measureable and it's far away from even close to zero overhead. 
But it's super useful. I guess having that capability in LTTng would be 
similarly useful and if it's documented to have an overhead people can use it 
with care.

Cheers

-- 
Milian Wolff | milian.wolff@kdab.com | Senior Software Engineer
KDAB (Deutschland) GmbH, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt, C++ and OpenGL Experts

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