chore(ansible): add ulimit execution to setenv_caret.bash

[takam5f2]

Signed-off-by: Takayuki AKAMINE takayuki.akamine@tier4.jp

Description

I want to add ulimit explanation to setenv_caret.bash.

After updating LTTng from 2.12 to 2.13, users have to mind the maximum number of file descriptor. I think that setenv_caret.bash must have some description for users to notice it.

Related links

https://tier4.github.io/CARET_doc/latest/recording/recording/#starting-lttng-session-manually

You may find that size of recorded data is strangely smaller than expected after updating LTTng to 2.13 if you apply CARET to a large application like Autoware which has hundreds of nodes. You have to suspect that maximum number of file descriptors is not enough in the case. You can check the number with ulimit -n command. The default maximum number is 1024, but it is not enough for the large application. You can avoid this problem by enlarging the maximum number with executing the command; ulimit -n 65536.

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