Performance Tuning

Neovim with many plugins can become slow if not carefully managed. This lesson shows how to profile and optimize.

Measure Startup Time

# Measure startup time from the command line
nvim --startuptime /tmp/startup.log && nvim +quit
cat /tmp/startup.log | sort -k2 -rn | head -20

" Inside Neovim with lazy.nvim
:Lazy profile

Lazy Loading (The Most Impactful Fix)

Every plugin that doesn't lazy-load increases startup time:

-- Bad: loads immediately
{
  "heavy/plugin",
}

-- Good: loads only when needed
{
  "heavy/plugin",
  event = { "BufReadPost", "BufNewFile" },  -- on file open
  -- or:
  cmd = "HeavyCommand",   -- on command
  -- or:
  ft = { "python" },      -- on filetype
  -- or:
  keys = { "<leader>xx" },  -- on keypress
}

Lazy Loading Priority

Load trigger	When it loads
lazy = false	Immediately (only for critical plugins)
event = "VimEnter"	Right after Vim starts
event = "VeryLazy"	After everything else
event = "BufReadPost"	When opening a file
ft = "python"	Only for Python files
cmd = "Cmd"	Only when command is used
keys = { "..." }	Only when key is pressed

Disable Unused Built-ins

in lazy.setup() options

performance = {
  rtp = {
    disabled_plugins = {
      "gzip",
      "matchit",
      "matchparen",
      "netrwPlugin",    -- if using neo-tree
      "tarPlugin",
      "tohtml",
      "tutor",
      "zipPlugin",
    },
  },
},

Large File Optimizations

lua/config/autocmds.lua

vim.api.nvim_create_autocmd("BufReadPre", {
  callback = function(args)
    local max_filesize = 500 * 1024  -- 500KB
    local ok, stats = pcall(vim.loop.fs_stat, args.file)
    if ok and stats and stats.size > max_filesize then
      -- Disable heavy features for large files
      vim.b.large_file = true
      vim.opt_local.syntax = "off"
      vim.opt_local.swapfile = false
      vim.opt_local.foldmethod = "manual"
      vim.opt_local.undolevels = -1
      vim.cmd("LspStop")
      vim.notify("Large file: disabling LSP, syntax, undo", vim.log.levels.WARN)
    end
  end,
})

Treesitter Performance

-- Disable for large files
highlight = {
  enable = true,
  disable = function(lang, buf)
    local max_filesize = 100 * 1024  -- 100KB
    local ok, stats = pcall(vim.loop.fs_stat, vim.api.nvim_buf_get_name(buf))
    if ok and stats and stats.size > max_filesize then
      return true
    end
  end,
},

Check Memory Usage

# Memory used by Neovim process
ps -o pid,rss,comm -p $(pgrep nvim)

# Inside Neovim
:lua print(collectgarbage("count") .. " KB Lua memory")

Profiling Lua Code

-- Profile a specific plugin config
local start = vim.loop.hrtime()
require("heavy.plugin").setup({})
local end_ = vim.loop.hrtime()
print(("Setup took %.2f ms"):format((end_ - start) / 1e6))

Quick Performance Checklist

• All plugins use event, cmd, ft, or keys for lazy loading
• Built-in unused plugins disabled in lazy.setup()
• LSP updatetime set to 300
• Large file autocmd disables heavy features
• Treesitter highlight disabled for large files
• swapfile = false (avoids disk I/O)
• Startup time measured with :Lazy profile

What's Next

• Cheatsheet