Merge pull request #10905 from erw7/vim-8.1.0475

vim-patch:8.1.{475,800,868,1007,1027,1031,1033,1037,1058,1435,1484,1485}

src/nvim/eval.c

@@ -444,7 +444,7 @@ void eval_clear(void)
   // unreferenced lists and dicts
   (void)garbage_collect(false);
 
-  // functions
+  // functions not garbage collected
   free_all_functions();
 }
 
@@ -873,17 +873,19 @@ char_u *eval_to_string(char_u *arg, char_u **nextcmd, int convert)
 char_u *eval_to_string_safe(char_u *arg, char_u **nextcmd, int use_sandbox)
 {
   char_u      *retval;
-  void        *save_funccalp;
+  funccal_entry_T funccal_entry;
 
-  save_funccalp = save_funccal();
+  save_funccal(&funccal_entry);
-  if (use_sandbox)
+  if (use_sandbox) {
-    ++sandbox;
+    sandbox++;
-  ++textlock;
+  }
-  retval = eval_to_string(arg, nextcmd, FALSE);
+  textlock++;
-  if (use_sandbox)
+  retval = eval_to_string(arg, nextcmd, false);
-    --sandbox;
+  if (use_sandbox) {
-  --textlock;
+    sandbox--;
-  restore_funccal(save_funccalp);
+  }
+  textlock--;
+  restore_funccal();
   return retval;
 }
 
@@ -5026,7 +5028,7 @@ bool garbage_collect(bool testing)
 
     // 3. Check if any funccal can be freed now.
     //    This may call us back recursively.
-    did_free = did_free || free_unref_funccal(copyID, testing);
+    did_free = free_unref_funccal(copyID, testing) || did_free;
   } else if (p_verbose > 0) {
     verb_msg(_(
         "Not enough memory to set references, garbage collection aborted!"));
@@ -9766,9 +9768,11 @@ const void *var_shada_iter(const void *const iter, const char **const name,
 
 void var_set_global(const char *const name, typval_T vartv)
 {
-  funccall_T *const saved_funccal = (funccall_T *)save_funccal();
+  funccal_entry_T funccall_entry;
+
+  save_funccal(&funccall_entry);
   set_var(name, strlen(name), &vartv, false);
-  restore_funccal(saved_funccal);
+  restore_funccal();
 }
 
 int store_session_globals(FILE *fd)
@@ -10324,8 +10328,10 @@ typval_T eval_call_provider(char *provider, char *method, list_T *arguments)
     .autocmd_fname = autocmd_fname,
     .autocmd_match = autocmd_match,
     .autocmd_bufnr = autocmd_bufnr,
-    .funccalp = save_funccal()
+    .funccalp = (void *)get_current_funccal()
   };
+  funccal_entry_T funccal_entry;
+  save_funccal(&funccal_entry);
   provider_call_nesting++;
 
   typval_T argvars[3] = {
@@ -10352,7 +10358,7 @@ typval_T eval_call_provider(char *provider, char *method, list_T *arguments)
 
   tv_list_unref(arguments);
   // Restore caller scope information
-  restore_funccal(provider_caller_scope.funccalp);
+  restore_funccal();
   provider_caller_scope = saved_provider_caller_scope;
   provider_call_nesting--;
   assert(provider_call_nesting >= 0);

src/nvim/eval/funcs.c

@@ -7243,7 +7243,7 @@ static void f_rpcrequest(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   uint8_t *save_sourcing_name, *save_autocmd_fname, *save_autocmd_match;
   linenr_T save_sourcing_lnum;
   int save_autocmd_bufnr;
-  void *save_funccalp;
+  funccal_entry_T funccal_entry;
 
   if (l_provider_call_nesting) {
     // If this is called from a provider function, restore the scope
@@ -7254,7 +7254,7 @@ static void f_rpcrequest(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     save_autocmd_fname = autocmd_fname;
     save_autocmd_match = autocmd_match;
     save_autocmd_bufnr = autocmd_bufnr;
-    save_funccalp = save_funccal();
+    save_funccal(&funccal_entry);
 
     current_sctx = provider_caller_scope.script_ctx;
     sourcing_name = provider_caller_scope.sourcing_name;
@@ -7262,7 +7262,7 @@ static void f_rpcrequest(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     autocmd_fname = provider_caller_scope.autocmd_fname;
     autocmd_match = provider_caller_scope.autocmd_match;
     autocmd_bufnr = provider_caller_scope.autocmd_bufnr;
-    restore_funccal(provider_caller_scope.funccalp);
+    set_current_funccal((funccall_T *)(provider_caller_scope.funccalp));
   }
 
 
@@ -7280,7 +7280,7 @@ static void f_rpcrequest(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     autocmd_fname = save_autocmd_fname;
     autocmd_match = save_autocmd_match;
     autocmd_bufnr = save_autocmd_bufnr;
-    restore_funccal(save_funccalp);
+    restore_funccal();
   }
 
   if (ERROR_SET(&err)) {

src/nvim/eval/typval_encode.c.h

@@ -607,7 +607,7 @@ _convert_one_value_regular_dict: {}
                                              kMPConvDict);
       TYPVAL_ENCODE_CONV_DICT_START(tv, tv->vval.v_dict,
                                     tv->vval.v_dict->dv_hashtab.ht_used);
-      assert(saved_copyID != copyID && saved_copyID != copyID - 1);
+      assert(saved_copyID != copyID);
       _mp_push(*mpstack, ((MPConvStackVal) {
         .tv = tv,
         .type = kMPConvDict,

src/nvim/eval/userfunc.c

@@ -43,11 +43,11 @@ hashtab_T func_hashtab;
 static garray_T funcargs = GA_EMPTY_INIT_VALUE;
 
 // pointer to funccal for currently active function
-funccall_T *current_funccal = NULL;
+static funccall_T *current_funccal = NULL;
 
 // Pointer to list of previously used funccal, still around because some
 // item in it is still being used.
-funccall_T *previous_funccal = NULL;
+static funccall_T *previous_funccal = NULL;
 
 static char *e_funcexts = N_(
     "E122: Function %s already exists, add ! to replace it");
@@ -541,14 +541,8 @@ static void add_nr_var(dict_T *dp, dictitem_T *v, char *name, varnumber_T nr)
   v->di_tv.vval.v_number = nr;
 }
 
-/*
+// Free "fc"
- * Free "fc" and what it contains.
+static void free_funccal(funccall_T *fc)
- */
-static void
-free_funccal(
-    funccall_T *fc,
-    int free_val              // a: vars were allocated
-)
 {
   for (int i = 0; i < fc->fc_funcs.ga_len; i++) {
     ufunc_T *fp = ((ufunc_T **)(fc->fc_funcs.ga_data))[i];
@@ -563,34 +557,74 @@ free_funccal(
   }
   ga_clear(&fc->fc_funcs);
 
-  // The a: variables typevals may not have been allocated, only free the
+  func_ptr_unref(fc->func);
-  // allocated variables.
+  xfree(fc);
-  vars_clear_ext(&fc->l_avars.dv_hashtab, free_val);
+}
 
+// Free "fc" and what it contains.
+// Can be called only when "fc" is kept beyond the period of it called,
+// i.e. after cleanup_function_call(fc).
+static void free_funccal_contents(funccall_T *fc)
+{
   // Free all l: variables.
   vars_clear(&fc->l_vars.dv_hashtab);
 
-  // Free the a:000 variables if they were allocated.
+  // Free all a: variables.
-  if (free_val) {
+  vars_clear(&fc->l_avars.dv_hashtab);
-    TV_LIST_ITER(&fc->l_varlist, li, {
-      tv_clear(TV_LIST_ITEM_TV(li));
-    });
-  }
 
-  func_ptr_unref(fc->func);
+  // Free the a:000 variables.
-  xfree(fc);
+  TV_LIST_ITER(&fc->l_varlist, li, {
+    tv_clear(TV_LIST_ITEM_TV(li));
+  });
+
+  free_funccal(fc);
 }
 
 /// Handle the last part of returning from a function: free the local hashtable.
 /// Unless it is still in use by a closure.
 static void cleanup_function_call(funccall_T *fc)
 {
+  bool may_free_fc = fc->fc_refcount <= 0;
+  bool free_fc = true;
+
   current_funccal = fc->caller;
 
-  // If the a:000 list and the l: and a: dicts are not referenced and there
+  // Free all l: variables if not referred.
-  // is no closure using it, we can free the funccall_T and what's in it.
+  if (may_free_fc && fc->l_vars.dv_refcount == DO_NOT_FREE_CNT) {
-  if (!fc_referenced(fc)) {
+    vars_clear(&fc->l_vars.dv_hashtab);
-    free_funccal(fc, false);
+  } else {
+    free_fc = false;
+  }
+
+  // If the a:000 list and the l: and a: dicts are not referenced and
+  // there is no closure using it, we can free the funccall_T and what's
+  // in it.
+  if (may_free_fc && fc->l_avars.dv_refcount == DO_NOT_FREE_CNT) {
+    vars_clear_ext(&fc->l_avars.dv_hashtab, false);
+  } else {
+    free_fc = false;
+
+    // Make a copy of the a: variables, since we didn't do that above.
+    TV_DICT_ITER(&fc->l_avars, di, {
+      tv_copy(&di->di_tv, &di->di_tv);
+    });
+  }
+
+  if (may_free_fc && fc->l_varlist.lv_refcount   // NOLINT(runtime/deprecated)
+      == DO_NOT_FREE_CNT) {
+    fc->l_varlist.lv_first = NULL;  // NOLINT(runtime/deprecated)
+
+  } else {
+    free_fc = false;
+
+    // Make a copy of the a:000 items, since we didn't do that above.
+    TV_LIST_ITER(&fc->l_varlist, li, {
+      tv_copy(TV_LIST_ITEM_TV(li), TV_LIST_ITEM_TV(li));
+    });
+  }
+
+  if (free_fc) {
+    free_funccal(fc);
   } else {
     static int made_copy = 0;
 
@@ -600,19 +634,12 @@ static void cleanup_function_call(funccall_T *fc)
     fc->caller = previous_funccal;
     previous_funccal = fc;
 
-    // Make a copy of the a: variables, since we didn't do that above.
+    if (want_garbage_collect) {
-    TV_DICT_ITER(&fc->l_avars, di, {
+      // If garbage collector is ready, clear count.
-      tv_copy(&di->di_tv, &di->di_tv);
+      made_copy = 0;
-    });
+    } else if (++made_copy >= (int)((4096 * 1024) / sizeof(*fc))) {
-
+      // We have made a lot of copies, worth 4 Mbyte.  This can happen
-    // Make a copy of the a:000 items, since we didn't do that above.
+      // when repetitively calling a function that creates a reference to
-    TV_LIST_ITER(&fc->l_varlist, li, {
-      tv_copy(TV_LIST_ITEM_TV(li), TV_LIST_ITEM_TV(li));
-    });
-
-    if (++made_copy == 10000) {
-      // We have made a lot of copies.  This can happen when
-      // repetitively calling a function that creates a reference to
       // itself somehow.  Call the garbage collector soon to avoid using
       // too much memory.
       made_copy = 0;
@@ -639,7 +666,7 @@ static void funccal_unref(funccall_T *fc, ufunc_T *fp, bool force)
     for (pfc = &previous_funccal; *pfc != NULL; pfc = &(*pfc)->caller) {
       if (fc == *pfc) {
         *pfc = fc->caller;
-        free_funccal(fc, true);
+        free_funccal_contents(fc);
         return;
       }
     }
@@ -766,7 +793,7 @@ void call_user_func(ufunc_T *fp, int argcount, typval_T *argvars,
   // check for CTRL-C hit
   line_breakcheck();
   // prepare the funccall_T structure
-  fc = xmalloc(sizeof(funccall_T));
+  fc = xcalloc(1, sizeof(funccall_T));
   fc->caller = current_funccal;
   current_funccal = fc;
   fc->func = fp;
@@ -881,9 +908,11 @@ void call_user_func(ufunc_T *fp, int argcount, typval_T *argvars,
     }
 
     if (ai >= 0 && ai < MAX_FUNC_ARGS) {
-      tv_list_append(&fc->l_varlist, &fc->l_listitems[ai]);
+      listitem_T *li = &fc->l_listitems[ai];
-      *TV_LIST_ITEM_TV(&fc->l_listitems[ai]) = argvars[i];
+
-      TV_LIST_ITEM_TV(&fc->l_listitems[ai])->v_lock = VAR_FIXED;
+      *TV_LIST_ITEM_TV(li) = argvars[i];
+      TV_LIST_ITEM_TV(li)->v_lock =  VAR_FIXED;
+      tv_list_append(&fc->l_varlist, li);
     }
   }
 
@@ -1106,21 +1135,26 @@ static bool func_name_refcount(char_u *name)
   return isdigit(*name) || *name == '<';
 }
 
-/*
+static funccal_entry_T *funccal_stack = NULL;
- * Save the current function call pointer, and set it to NULL.
- * Used when executing autocommands and for ":source".
- */
-void *save_funccal(void)
-{
-  funccall_T *fc = current_funccal;
 
+// Save the current function call pointer, and set it to NULL.
+// Used when executing autocommands and for ":source".
+void save_funccal(funccal_entry_T *entry)
+{
+  entry->top_funccal = current_funccal;
+  entry->next = funccal_stack;
+  funccal_stack = entry;
   current_funccal = NULL;
-  return (void *)fc;
 }
 
-void restore_funccal(void *vfc)
+void restore_funccal(void)
 {
-  current_funccal = (funccall_T *)vfc;
+  if (funccal_stack == NULL) {
+    IEMSG("INTERNAL: restore_funccal()");
+  } else {
+    current_funccal = funccal_stack->top_funccal;
+    funccal_stack = funccal_stack->next;
+  }
 }
 
 funccall_T *get_current_funccal(void)
@@ -1128,6 +1162,11 @@ funccall_T *get_current_funccal(void)
   return current_funccal;
 }
 
+void set_current_funccal(funccall_T *fc)
+{
+  current_funccal = fc;
+}
+
 #if defined(EXITFREE)
 void free_all_functions(void)
 {
@@ -1137,10 +1176,13 @@ void free_all_functions(void)
   uint64_t todo = 1;
   uint64_t used;
 
-  // Clean up the call stack.
+  // Clean up the current_funccal chain and the funccal stack.
   while (current_funccal != NULL) {
     tv_clear(current_funccal->rettv);
     cleanup_function_call(current_funccal);
+    if (current_funccal == NULL && funccal_stack != NULL) {
+      restore_funccal();
+    }
   }
 
   // First clear what the functions contain. Since this may lower the
@@ -3121,7 +3163,7 @@ bool free_unref_funccal(int copyID, int testing)
     if (can_free_funccal(*pfc, copyID)) {
       funccall_T *fc = *pfc;
       *pfc = fc->caller;
-      free_funccal(fc, true);
+      free_funccal_contents(fc);
       did_free = true;
       did_free_funccal = true;
     } else {
@@ -3314,9 +3356,18 @@ bool set_ref_in_call_stack(int copyID)
   bool abort = false;
 
   for (funccall_T *fc = current_funccal; fc != NULL; fc = fc->caller) {
-    abort = abort || set_ref_in_ht(&fc->l_vars.dv_hashtab, copyID, NULL);
+    abort = abort || set_ref_in_funccal(fc, copyID);
-    abort = abort || set_ref_in_ht(&fc->l_avars.dv_hashtab, copyID, NULL);
   }
+
+  // Also go through the funccal_stack.
+  for (funccal_entry_T *entry = funccal_stack; entry != NULL;
+       entry = entry->next) {
+    for (funccall_T *fc = entry->top_funccal; !abort && fc != NULL;
+         fc = fc->caller) {
+      abort = abort || set_ref_in_funccal(fc, copyID);
+    }
+  }
+
   return abort;
 }
 

src/nvim/eval/userfunc.h

@@ -11,6 +11,12 @@ typedef struct {
   dictitem_T  *fd_di;  ///< Dictionary item used.
 } funcdict_T;
 
+typedef struct funccal_entry funccal_entry_T;
+struct funccal_entry {
+  void *top_funccal;
+  funccal_entry_T *next;
+};
+
 /// errors for when calling a function
 typedef enum {
   ERROR_UNKNOWN = 0,

src/nvim/ex_cmds2.c

@@ -3107,7 +3107,6 @@ int do_source(char_u *fname, int check_other, int is_vimrc)
   int retval = FAIL;
   static scid_T last_current_SID = 0;
   static int last_current_SID_seq = 0;
-  void                    *save_funccalp;
   int save_debug_break_level = debug_break_level;
   scriptitem_T            *si = NULL;
   proftime_T wait_start;
@@ -3228,7 +3227,8 @@ int do_source(char_u *fname, int check_other, int is_vimrc)
 
   // Don't use local function variables, if called from a function.
   // Also starts profiling timer for nested script.
-  save_funccalp = save_funccal();
+  funccal_entry_T funccalp_entry;
+  save_funccal(&funccalp_entry);
 
   // Check if this script was sourced before to finds its SID.
   // If it's new, generate a new SID.
@@ -3353,7 +3353,7 @@ int do_source(char_u *fname, int check_other, int is_vimrc)
   }
 
   current_sctx = save_current_sctx;
-  restore_funccal(save_funccalp);
+  restore_funccal();
   if (l_do_profiling == PROF_YES) {
     prof_child_exit(&wait_start);    // leaving a child now
   }

src/nvim/fileio.c

@@ -6736,7 +6736,6 @@ static bool apply_autocmds_group(event_T event, char_u *fname, char_u *fname_io,
   static int nesting = 0;
   AutoPatCmd patcmd;
   AutoPat     *ap;
-  void        *save_funccalp;
   char_u      *save_cmdarg;
   long save_cmdbang;
   static int filechangeshell_busy = FALSE;
@@ -6926,8 +6925,9 @@ static bool apply_autocmds_group(event_T event, char_u *fname, char_u *fname_io,
   if (do_profiling == PROF_YES)
     prof_child_enter(&wait_time);     /* doesn't count for the caller itself */
 
-  /* Don't use local function variables, if called from a function */
+  // Don't use local function variables, if called from a function.
-  save_funccalp = save_funccal();
+  funccal_entry_T funccal_entry;
+  save_funccal(&funccal_entry);
 
   /*
    * When starting to execute autocommands, save the search patterns.
@@ -7016,9 +7016,10 @@ static bool apply_autocmds_group(event_T event, char_u *fname, char_u *fname_io,
   autocmd_bufnr = save_autocmd_bufnr;
   autocmd_match = save_autocmd_match;
   current_sctx = save_current_sctx;
-  restore_funccal(save_funccalp);
+  restore_funccal();
-  if (do_profiling == PROF_YES)
+  if (do_profiling == PROF_YES) {
     prof_child_exit(&wait_time);
+  }
   KeyTyped = save_KeyTyped;
   xfree(fname);
   xfree(sfname);

src/nvim/testdir/runtest.vim

@@ -44,6 +44,10 @@ if &lines < 24 || &columns < 80
   qa!
 endif
 
+if has('reltime')
+  let s:start_time = reltime()
+endif
+
 " Common with all tests on all systems.
 source setup.vim
 
@@ -100,6 +104,9 @@ endfunc
 
 func RunTheTest(test)
   echo 'Executing ' . a:test
+  if has('reltime')
+    let func_start = reltime()
+  endif
 
   " Avoid stopping at the "hit enter" prompt
   set nomore
@@ -124,7 +131,11 @@ func RunTheTest(test)
     endtry
   endif
 
-  call add(s:messages, 'Executing ' . a:test)
+  let message = 'Executed ' . a:test
+  if has('reltime')
+    let message ..= ' in ' .. reltimestr(reltime(func_start)) .. ' seconds'
+  endif
+  call add(s:messages, message)
   let s:done += 1
 
   if a:test =~ 'Test_nocatch_'
@@ -230,6 +241,9 @@ func FinishTesting()
   else
     let message = 'Executed ' . s:done . (s:done > 1 ? ' tests' : ' test')
   endif
+  if has('reltime')
+    let message ..= ' in ' .. reltimestr(reltime(s:start_time)) .. ' seconds'
+  endif
   echo message
   call add(s:messages, message)
   if s:fail > 0

test/functional/legacy/memory_usage_spec.lua

@@ -0,0 +1,161 @@
+local helpers = require('test.functional.helpers')(after_each)
+local clear = helpers.clear
+local eval = helpers.eval
+local eq = helpers.eq
+local feed_command = helpers.feed_command
+local iswin = helpers.iswin
+local retry = helpers.retry
+local ok = helpers.ok
+local source = helpers.source
+
+local monitor_memory_usage = {
+  memory_usage = function(self)
+    local handle
+    if iswin() then
+      handle = io.popen('wmic process where processid=' ..self.pid..' get WorkingSetSize')
+    else
+      handle = io.popen('ps -o rss= -p '..self.pid)
+    end
+    return tonumber(handle:read('*a'):match('%d+'))
+  end,
+  op = function(self)
+    retry(nil, 10000, function()
+      local val = self.memory_usage(self)
+      if self.max < val then
+        self.max = val
+      end
+      table.insert(self.hist, val)
+      ok(#self.hist > 20)
+      local result = {}
+      for key,value in ipairs(self.hist) do
+        if value ~= self.hist[key + 1] then
+          table.insert(result, value)
+        end
+      end
+      table.remove(self.hist, 1)
+      self.last = self.hist[#self.hist]
+      eq(#result, 1)
+    end)
+  end,
+  dump = function(self)
+    return 'max: '..self.max ..', last: '..self.last
+  end,
+  monitor_memory_usage = function(self, pid)
+    local obj = {
+      pid = pid,
+      max = 0,
+      last = 0,
+      hist = {},
+    }
+    setmetatable(obj, { __index = self })
+    obj:op()
+    return obj
+  end
+}
+setmetatable(monitor_memory_usage,
+{__call = function(self, pid)
+  return monitor_memory_usage.monitor_memory_usage(self, pid)
+end})
+
+describe('memory usage', function()
+  local function check_result(tbl, status, result)
+    if not status then
+      print('')
+      for key, val in pairs(tbl) do
+        print(key, val:dump())
+      end
+      error(result)
+    end
+  end
+
+  local function isasan()
+    local version = eval('execute("version")')
+    return version:match('-fsanitize=[a-z,]*address')
+  end
+
+  before_each(clear)
+
+  --[[
+  Case: if a local variable captures a:000, funccall object will be free
+  just after it finishes.
+  ]]--
+  it('function capture vargs', function()
+    if isasan() then
+      pending('ASAN build is difficult to estimate memory usage')
+    end
+    if iswin() and eval("executable('wmic')")  == 0 then
+      pending('missing "wmic" command')
+    elseif eval("executable('ps')")  == 0 then
+      pending('missing "ps" command')
+    end
+
+    local pid = eval('getpid()')
+    local before = monitor_memory_usage(pid)
+    source([[
+      func s:f(...)
+        let x = a:000
+      endfunc
+      for _ in range(10000)
+        call s:f(0)
+      endfor
+    ]])
+    local after = monitor_memory_usage(pid)
+    -- Estimate the limit of max usage as 2x initial usage.
+    -- The lower limit can fluctuate a bit, use 97%.
+    check_result({before=before, after=after},
+                 pcall(ok, before.last * 97 / 100 < after.max))
+    check_result({before=before, after=after},
+                 pcall(ok, before.last * 2 > after.max))
+    -- In this case, garbage collecting is not needed.
+    -- The value might fluctuate a bit, allow for 3% tolerance below and 5% above.
+    -- Based on various test runs.
+    local lower = after.last * 97 / 100
+    local upper = after.last * 105 / 100
+    check_result({before=before, after=after}, pcall(ok, lower < after.max))
+    check_result({before=before, after=after}, pcall(ok, after.max < upper))
+  end)
+
+  --[[
+  Case: if a local variable captures l: dict, funccall object will not be
+  free until garbage collector runs, but after that memory usage doesn't
+  increase so much even when rerun Xtest.vim since system memory caches.
+  ]]--
+  it('function capture lvars', function()
+    if isasan() then
+      pending('ASAN build is difficult to estimate memory usage')
+    end
+    if iswin() and eval("executable('wmic')")  == 0 then
+      pending('missing "wmic" command')
+    elseif eval("executable('ps')")  == 0 then
+      pending('missing "ps" command')
+    end
+
+    local pid = eval('getpid()')
+    local before = monitor_memory_usage(pid)
+    local fname = source([[
+      if !exists('s:defined_func')
+        func s:f()
+          let x = l:
+        endfunc
+      endif
+      let s:defined_func = 1
+      for _ in range(10000)
+        call s:f()
+      endfor
+    ]])
+    local after = monitor_memory_usage(pid)
+    for _ = 1, 3 do
+      feed_command('so '..fname)
+    end
+    local last = monitor_memory_usage(pid)
+    -- The usage may be a bit less than the last value, use 80%.
+    -- Allow for 20% tolerance at the upper limit. That's very permissive, but
+    -- otherwise the test fails sometimes.
+    local lower = before.last * 8 / 10
+    local upper = (after.max + (after.last - before.last)) * 12 / 10
+    check_result({before=before, after=after, last=last},
+                 pcall(ok, lower < last.last))
+    check_result({before=before, after=after, last=last},
+                 pcall(ok, last.last < upper))
+  end)
+end)