Briefly, Spacemacs is extremely slow when I use describe commands (C-h m, C-h v, ...). I ran an experiment with two identical machines. The only difference were the version of Emacs: 28.0.50 and 27.1.91.
The machine with version 27.1.91 is of order of magnitude faster. The output of the profiler is included below:
Machine with Emacs 28.0.50 and Spacemacs configuration:
It appears that help-fns--list-local-commands is the source of the problem.
Please let me know if you need any further information.
In GNU Emacs 28.0.50 (build 1, x86_64-apple-darwin19.6.0, NS appkit-1894.60 Version 10.15.7 (Build 19H114)) of 2021-03-22 built on naveeds-MacBook-Pro.local Windowing system distributor 'Apple', version 10.3.1894 System Description: Mac OS X 10.15.7
Important settings: value of $LANG: en_US.UTF-8 locale-coding-system: utf-8-unix
Major mode: Spacemacs buffer
Minor modes in effect: evil-escape-mode: t global-display-line-numbers-mode: t projectile-mode: t recentf-mode: t winner-mode: t winum-mode: t pupo-mode: t global-vi-tilde-fringe-mode: t global-undo-tree-mode: t undo-tree-mode: t spaceline-info-mode: t spaceline-helm-mode: t save-place-mode: t savehist-mode: t persp-mode: t global-hl-todo-mode: t purpose-mode: t eyebrowse-mode: t global-anzu-mode: t anzu-mode: t editorconfig-mode: t counsel-mode: t ivy-mode: t clean-aindent-mode: t hybrid-mode: t which-key-mode: t override-global-mode: t shell-dirtrack-mode: t evil-mode: t evil-local-mode: t spacemacs-leader-override-mode: t global-spacemacs-leader-override-mode: t global-hl-line-mode: t xterm-mouse-mode: t global-auto-revert-mode: t ido-vertical-mode: t global-page-break-lines-mode: t page-break-lines-mode: t global-eldoc-mode: t electric-indent-mode: t mouse-wheel-mode: t menu-bar-mode: t file-name-shadow-mode: t global-font-lock-mode: t font-lock-mode: t auto-composition-mode: t auto-encryption-mode: t auto-compression-mode: t buffer-read-only: t column-number-mode: t line-number-mode: t transient-mark-mode: t