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.

runtime/lua/vim/highlight.lua

@@ -129,13 +129,13 @@ function M.on_yank(opts)
     yank_cancel()
   end
 
+  vim.api.nvim_win_add_ns(winid, yank_ns)
   M.range(bufnr, yank_ns, higroup, "'[", "']", {
     regtype = event.regtype,
     inclusive = event.inclusive,
     priority = opts.priority or M.priorities.user,
     _scoped = true,
   })
-  vim.api.nvim_win_add_ns(winid, yank_ns)
 
   yank_cancel = function()
     yank_timer = nil

src/nvim/api/extmark.c

@@ -1234,7 +1234,9 @@ Boolean nvim_win_add_ns(Window window, Integer ns_id, Error *err)
 
   set_put(uint32_t, &win->w_ns_set, (uint32_t)ns_id);
 
-  changed_window_setting(win);
+  if (map_has(uint32_t, win->w_buffer->b_extmark_ns, (uint32_t)ns_id)) {
+    changed_window_setting(win);
+  }
 
   return true;
 }
@@ -1279,7 +1281,9 @@ Boolean nvim_win_remove_ns(Window window, Integer ns_id, Error *err)
 
   set_del(uint32_t, &win->w_ns_set, (uint32_t)ns_id);
 
-  changed_window_setting(win);
+  if (map_has(uint32_t, win->w_buffer->b_extmark_ns, (uint32_t)ns_id)) {
+    changed_window_setting(win);
+  }
 
   return true;
 }

src/nvim/extmark.c

@@ -206,7 +206,9 @@ bool extmark_clear(buf_T *buf, uint32_t ns_id, int l_row, colnr_T l_col, int u_r
     }
   }
 
-  bool marks_cleared = false;
+  bool marks_cleared_any = false;
+  bool marks_cleared_all = l_row == 0 && l_col == 0;
+
   MarkTreeIter itr[1] = { 0 };
   marktree_itr_get(buf->b_marktree, l_row, l_col, itr);
   while (true) {
@@ -214,16 +216,29 @@ bool extmark_clear(buf_T *buf, uint32_t ns_id, int l_row, colnr_T l_col, int u_r
     if (mark.pos.row < 0
         || mark.pos.row > u_row
         || (mark.pos.row == u_row && mark.pos.col > u_col)) {
+      if (mark.pos.row >= 0) {
+        marks_cleared_all = false;
+      }
       break;
     }
     if (mark.ns == ns_id || all_ns) {
-      marks_cleared = true;
+      marks_cleared_any = true;
       extmark_del(buf, itr, mark, true);
     } else {
       marktree_itr_next(buf->b_marktree, itr);
     }
   }
-  return marks_cleared;
+
+  if (marks_cleared_all) {
+    if (all_ns) {
+      map_destroy(uint32_t, buf->b_extmark_ns);
+      *buf->b_extmark_ns = (Map(uint32_t, uint32_t)) MAP_INIT;
+    } else {
+      map_del(uint32_t, uint32_t)(buf->b_extmark_ns, ns_id, NULL);
+    }
+  }
+
+  return marks_cleared_any;
 }
 
 /// @return  the position of marks between a range,
@@ -315,10 +330,6 @@ MTPair extmark_from_id(buf_T *buf, uint32_t ns_id, uint32_t id)
 /// free extmarks from the buffer
 void extmark_free_all(buf_T *buf)
 {
-  if (!map_size(buf->b_extmark_ns)) {
-    return;
-  }
-
   MarkTreeIter itr[1] = { 0 };
   marktree_itr_get(buf->b_marktree, 0, 0, itr);
   while (true) {

src/nvim/memfile.c

@@ -677,7 +677,7 @@ static int mf_trans_add(memfile_T *mfp, bhdr_T *hp)
 ///          The old number           When not found.
 blocknr_T mf_trans_del(memfile_T *mfp, blocknr_T old_nr)
 {
-  blocknr_T *num = map_ref(int64_t, int64_t)(&mfp->mf_trans, old_nr, false);
+  blocknr_T *num = map_ref(int64_t, int64_t)(&mfp->mf_trans, old_nr, NULL);
   if (num == NULL) {  // not found
     return old_nr;
   }

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)

test/functional/api/extmark_spec.lua

@@ -1896,6 +1896,24 @@ describe('Extmarks buffer api with many marks', function()
     end
     eq(ns_marks[ns1], get_marks(ns1))
     eq(ns_marks[ns2], get_marks(ns2))
+
+    api.nvim_buf_clear_namespace(0, ns1, 0, 10)
+    for id, mark in pairs(ns_marks[ns1]) do
+      if mark[1] < 10 then
+        ns_marks[ns1][id] = nil
+      end
+    end
+    eq(ns_marks[ns1], get_marks(ns1))
+    eq(ns_marks[ns2], get_marks(ns2))
+
+    api.nvim_buf_clear_namespace(0, ns1, 20, -1)
+    for id, mark in pairs(ns_marks[ns1]) do
+      if mark[1] >= 20 then
+        ns_marks[ns1][id] = nil
+      end
+    end
+    eq(ns_marks[ns1], get_marks(ns1))
+    eq(ns_marks[ns2], get_marks(ns2))
   end)
 
   it('can delete line', function()