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 a 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 email to support@alcf.anl.gov detailing the reason you are disabling it