On Ubuntu 20.04.3 LTS, I'm using the self compiled Emacs git master
version. I find there is a very long completion delay time in LISP
interaction mode. For example, when I type `(map)' in scratch buffer,
there will have 5070 candidates as shown in the attached file, and the
completion delay is about 2-5 seconds.

Any hints to improve this phenomenon?

Regards
-- 
Assoc. Prof. Hongyi Zhao <hongyi.zhao@gmail.com>
Theory and Simulation of Materials
Hebei Vocational University of Technology and Engineering
No. 473, Quannan West Street, Xindu District, Xingtai, Hebei province