Re: [lttng-dev] Profiling LTTng tracepoint latency on different arm platforms

["Yitschak, Yehuda via lttng-dev" <lttng-dev@lists.lttng.org>]

> On 6/20/23 10:20, Mathieu Desnoyers via lttng-dev wrote:
> > On 6/20/23 06:27, Mousa, Anas via lttng-dev wrote:
> >> Hello,
> >
> >>
> >>
> Arethereanysuggestionstorootcausethehighlatencyandpotentiallyimproveito
> n*platform****1*?
> >>
> >> Thanks and best regards,
> >>
> >> Anas.
> >>
> >
> > I recommend using "perf" when tracing with the sample program in a
> > loop to figure out the hot spots. With that information on the "fast"
> > and "slow" system, we might be able to figure out what differs.
> >
> > Also, comparing the kernel configurations of the two systems can help.
> > Also comparing the glibc versions of the two systems would be relevant.
> >
> 
> Also make sure you benchmark the lttng "snapshot" mode [1] to make sure
> you don't run into a situation where the disk/network I/O throughput cannot
> cope with the generated event throughput, thus causing the ring buffer to
> discard events. This would therefore "speed up" tracing from the application
> perspective because discarding an event is faster than writing it to a ring
> buffer.

You mean we should avoid the "discard" loss mode and use "overwrite" loss mode since discard mode can fake fast performance ? 

> 
> Thanks,
> 
> Mathieu
> 
> [1] https://lttng.org/docs/v2.13/#doc-taking-a-snapshot
> 
> > Thanks,
> >
> > Mathieu
> >
> >
> 
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> https://www.efficios.com
> 
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