Conference notes for 2025 07 01

Lmod Zoom Mtg July 1st

• Q/A
• The theme of this meeting is
  • Release of Lmod Internal Code docs
  • what the %$^@!#& is going on with the Big Cache Branch?
• Lmod Internal Code documentation
  • Now provides a walking tour through the code for module load foo/1.0
  • Amazing work by Matthew Cawood to force different AI Agents to deliver readable docs.
  • Detailed overview of how things like mcp and mname work. The core magic of Lmod.
  • Lmod readthedocs
• Lmod 8.7.63 released
  • Internal data structures like dbT where rebuild everytime a dependent module was loaded
  • Complete rewrite of how dependencies are checked.
  • Better handling of how code strings are serialized. Things like escapes and double quotes.
• Old Dependency checking
  • Bet you didn't know that Lmod checks dependencies on load and unload.
  • Lmod used to re-read and evaluate modulefiles to check dependencies.
• New Dependency checking
  • Now dependencies are recorded in the ModuleTable for each module that has them
  • This is much much faster then the old way.

Big Cache results from Ward Poelmans in Brussels

• Trick to clear caches: echo 3 > /proc/sys/vm/drop_caches
• Fake case with 1 module that depends_on() 299 modules

Lmod version	Total Time
8.7.55:	40.2 seconds
8.7.63:	5.2 seconds
BigCache:	2.7 seconds

• Detailed results for big cache branch

Name	count	Total Time (seconds)
main	1	2.7237679958344
post_cmd	1	0.61693596839905
Shell:expand(varT)	1	0.59209012985229
Cache:build	1	0.42909407615662
performDependencyCk	1	0.0017750263214111
check_deps	299	0.001509428024292

Question: Is using the big cache (includes text of modules) worth it?

• It is a little faster but maybe not worth the trouble.
• Issue #773 Adding additional information to the spider database
  • Possibly record executables found in $PATH entry
  • Track other environment variables?