[lttng-dev] LTTng user mode performance observation

[Richard Schmitt]

We are trying to use user space LTTng to perform some performance analysis of fast-path layer 3 forwarding.  We have seen that with the tracepoints enabled, we experience about a 30% increase in service time.  This is spread out over two tracepoints so each one is still contributing a good amount.

This fast path is fast, about 300 cycles so we are asking a lot of efficiency of the tracepoint but for comparison, we implemented a simple ring buffer.  When we run with this type of capture, we only experience a 5% increase in service time.

I’m looking for pointers.  We’d rather use LTTng.  Are there ways to tune LTTng ust for ultra high performance requirements.  Perhaps there is  a way we could write directly to ust’s ring buffers, or perhaps preallocate the buffers?

Rich
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