Normally the Sublime Text editor is blazingly fast, but I find that Sublime Text 3 is nearly unusably slow while building the LSST software stack. The issue is that the symbol indexer is taking up too much CPU time. One solution is to simply disable indexing by setting "index_files": false in the preferences file. However, I find symbol lookup useful, so I would rather allow indexing.
The following posting describes a way to relieve the problem: https://forum.sublimetext.com/t/sublime-text-3-is-very-slow/19596/8
Based on that posting I have put the following in my user preferences file and it makes a huge improvement:
// Files and directories to ignore for indexing symbols
"index_exclude_patterns":
[
"*_wrap.cc",
"*Lib.py"
],
// Maximum number of cores to use for indexing; default is all
"index_workers": 2,