perf(extmarks): better track whether namespace has extmarks (#28615)

This avoids redraw when adding/removing an empty namespace for a window.

This also avoids marktree traversal when clearing a namespace that has
already been cleared, which is added as a benchmark.

1 files changed, 45 insertions, 0 deletions

diff --git a/test/benchmark/extmark_spec.lua b/test/benchmark/extmark_spec.lua
new file mode 100644
index 0000000000..0d284b363c
--- /dev/null
+++ b/test/benchmark/extmark_spec.lua
@@ -0,0 +1,45 @@
+local n = require('test.functional.testnvim')()
+
+local clear = n.clear
+local exec_lua = n.exec_lua
+
+describe('extmark perf', function()
+  before_each(function()
+    clear()
+
+    exec_lua([[
+      out = {}
+      function start()
+        ts = vim.uv.hrtime()
+      end
+      function stop(name)
+        out[#out+1] = ('%14.6f ms - %s'):format((vim.uv.hrtime() - ts) / 1000000, name)
+      end
+    ]])
+  end)
+
+  after_each(function()
+    for _, line in ipairs(exec_lua([[return out]])) do
+      print(line)
+    end
+  end)
+
+  it('repeatedly calling nvim_buf_clear_namespace #28615', function()
+    exec_lua([[
+      vim.api.nvim_buf_set_lines(0, 0, -1, true, { 'foo', 'bar' })
+      local ns0 = vim.api.nvim_create_namespace('ns0')
+      local ns1 = vim.api.nvim_create_namespace('ns1')
+
+      for _ = 1, 10000 do
+        vim.api.nvim_buf_set_extmark(0, ns0, 0, 0, {})
+      end
+      vim.api.nvim_buf_set_extmark(0, ns1, 1, 0, {})
+
+      start()
+      for _ = 1, 10000 do
+        vim.api.nvim_buf_clear_namespace(0, ns1, 0, -1)
+      end
+      stop('nvim_buf_clear_namespace')
+    ]])
+  end)
+end)