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

[Mathieu Desnoyers 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,
> 
>>
>> Arethereanysuggestionstorootcausethehighlatencyandpotentiallyimproveiton*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.

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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