Emacs was taking forever to start. Found the built-in profiler to track down the culprit.

The Commands

M-x profiler-start
# Do the slow thing (restart Emacs, open files, etc.)
M-x profiler-report

That’s it. Shows you what’s eating CPU time.

What I Found

In my case:

- 89% org-mode
  - 67% org-roam-db-sync
    - 45% emacsql queries

org-roam was syncing on every startup. Way too slow.

The Fix

;; Don't auto-sync on startup
(setq org-roam-db-autosync-mode nil)

;; Manually sync when needed
M-x org-roam-db-sync

Startup time: 15s → 2s

How It Works

Profiler samples your Emacs process and shows:

• Which functions are called most
• Where time is spent
• Call stack breakdown

Interactive report lets you expand/collapse call trees.

Other Uses

Not just for startup:

• Slow file opening
• Laggy commands
• Memory leaks (use profiler-start with memory profiling)

Alternative: esup

For startup-specific profiling:

# Install esup
M-x package-install RET esup

# Profile init file
M-x esup

Shows timing for each line in your init.el.

But built-in profiler works for everything, so I usually just use that.

Quick tip: if Emacs is slow, profile it. Don’t guess.