XALT

What is XALT?

XALT is a user build and execution tracking framework; it is installed at ALCF on Polaris to track library usage.

When XALT is enabled during builds:

• An XALT watermark is added to the ELF binary of the executable(s).
• An XALT link record containing information about the build is created.

When XALT is enabled during application executions:

• An XALT start run record containing information about the execution is created; some link data is also included if the executable was built with XALT.
• If the execution exits normally, an XALT end run record containing information about the end of the process is created; if the process exits abnormally, no end run record is created.
• For MPI jobs, XALT run records are produced only for rank 0.

XALT implementation details

• XALT uses an ld wrapper script to add the watermark to executables.
• XALT interposes an LD_PRELOAD library into the execution of the user's application. XALT runs as the user, with the user's primary and supplementary groups.

How to disable XALT

• Execute the command module unload xalt.
• If you disable XALT, please send an email to [email protected] detailing the reason you are disabling it.