[lttng-dev] Babeltrace performance issue in live-reading mode

[Jonathan Rajotte-Julien]

Hi,

On Mon, Sep 18, 2017 at 11:32:07AM +0800, liguang li wrote:
>    Hi,
> 
>    Create a session in live-reading mode, run a application which having very
>    high event throughput, then prints
>    the events with babeltrace. We found the live trace viewer are viewing
>    events a few seconds ago, and as time

Could you provide us the version used for babeltrace, lttng-tools and lttng-ust?

>    goes on, the delay will be bigger and bigger.

A similar issues was observed a couple months ago, which implicated multiple delayed ack
problems during communication between lttng-relayd and babeltrace.

The following fixes were merged:

[1] https://github.com/lttng/lttng-tools/commit/b6025e9476332b75eb8184345c3eb3e924780088
[2] https://github.com/efficios/babeltrace/commit/de417d04317ca3bc30f59685a9d19de670e4b11d
[3] https://github.com/efficios/babeltrace/commit/4594dbd8f7c2af2446a3e310bee74ba4a2e9d648

In the event that you are already using an updated version of babeltrace and
lttng-tools, it would be pertinent to provide us with a simple reproducer so we
can assess the issue.

Cheers

>    I checked the source code, found Babeltrace in live-reading mode will read
>    the recorded events in the CTF
>    files, and then parse and print it in a single thread. The process is a
>    little slow, do you have any ideas to
>    improve the process.
>    Thanks,
>    Liguang

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-- 
Jonathan Rajotte-Julien
EfficiOS