[GR-19220] Several gems need at least some value for total_allocated_objects (#2292)

PullRequest: truffleruby/2489

Author: eregon

CHANGELOG.md

@@ -67,6 +67,7 @@ Compatibility:
 * Implemented the `Time.at` `in:` parameter.
 * Implemented `Kernel#raise` `cause` parameter.
 * Improved compatibility of `Signal.trap` and `Kernel#trap` (#2287, @chrisseaton).
+* Implemented `GC.stat(:total_allocated_objects)` as `0` (#2292, @chrisseaton).
 
 Performance:
 

doc/user/compatibility.md

@@ -157,6 +157,10 @@ Additionally, `FPE`, `ILL`, `KILL`, `SEGV`, `STOP`, and `VTALRM` cannot be trapp
 
 When TruffleRuby is run as part of a polyglot application, any signals that are handled by another language become unavailable for TruffleRuby to trap.
 
+### GC statistics
+
+TruffleRuby provides similar `GC.stat` statistics to MRI, but not all statistics are available, and some statistics may be approximations. Use `GC.stat.keys` to see which are provided with real or approximate values. Missing values will return `0`.
+
 ## Features with Very Low Performance
 
 ### `ObjectSpace`

spec/ruby/core/gc/stat_spec.rb

@@ -1,19 +1,16 @@
 require_relative '../../spec_helper'
 
 describe "GC.stat" do
-  it "supports access by key" do
-    keys = [:heap_free_slots, :total_allocated_objects, :count]
-    keys.each do |key|
-      GC.stat(key).should be_kind_of(Integer)
-    end
-  end
-
   it "returns hash of values" do
     stat = GC.stat
     stat.should be_kind_of(Hash)
     stat.keys.should include(:count)
   end
 
+  it "can return a single value" do
+    GC.stat(:count).should be_kind_of(Integer)
+  end
+
   it "increases count after GC is run" do
     count = GC.stat(:count)
     GC.start
@@ -25,4 +22,19 @@
     GC.start
     GC.stat(:major_gc_count).should > count
   end
+
+  it "provides some number for count" do
+    GC.stat(:count).should be_kind_of(Integer)
+    GC.stat[:count].should be_kind_of(Integer)
+  end
+
+  it "provides some number for heap_free_slots" do
+    GC.stat(:heap_free_slots).should be_kind_of(Integer)
+    GC.stat[:heap_free_slots].should be_kind_of(Integer)
+  end
+
+  it "provides some number for total_allocated_objects" do
+    GC.stat(:total_allocated_objects).should be_kind_of(Integer)
+    GC.stat[:total_allocated_objects].should be_kind_of(Integer)
+  end
 end

src/main/ruby/truffleruby/core/gc.rb

@@ -75,11 +75,11 @@ def garbage_collect
     GC.start
   end
 
-  def self.stat(option = nil)
-    time, count, minor_count, major_count, unknown_count, heap, memory_pool_names, memory_pool_info = Primitive.gc_stat()
+  def self.stat(key = nil)
+    time, count, minor_count, major_count, unknown_count, heap, memory_pool_names, memory_pool_info = Primitive.gc_stat
     used, committed, init, max = heap
 
-    # Initialize stat for statistics that come from memory pools, and populate it with some final stats
+    # Initialize stat for statistics that come from memory pools, and populate it with some final stats (ordering similar to MRI)
     stat = {
       count: count,
       time: time,
@@ -93,48 +93,41 @@ def self.stat(option = nil)
       committed: committed,
       init: init,
       max: max,
-      peak_used: 0,
-      peak_committed: 0,
-      peak_init: 0,
-      peak_max: 0,
-      last_used: 0,
-      last_committed: 0,
-      last_init: 0,
-      last_max: 0,
     }
-
-    memory_pool_names.each_with_index do |memory_pool_name, i|
-      # Populate memory pool specific stats
-      info = memory_pool_info[i]
-      if info
-        stat[memory_pool_name] = data = {
-          used: info[0],
-          committed: info[1],
-          init: info[2],
-          max: info[3],
-          peak_used: info[4],
-          peak_committed: info[5],
-          peak_init: info[6],
-          peak_max: info[7],
-          last_used: info[8],
-          last_committed: info[9],
-          last_init: info[10],
-          last_max: info[11],
-        }
-
-        # Calculate stats across memory pools for peak_/last_ (we already know the values for current usage)
-        data.each_pair do |key, value|
-          stat[key] += value if key.start_with?('peak_', 'last_')
+    stat.default = 0
+
+    unless Primitive.object_kind_of?(key, Symbol) # memory_pool_names are Strings
+      memory_pool_names.each_with_index do |memory_pool_name, i|
+        # Populate memory pool specific stats
+        info = memory_pool_info[i]
+        if info
+          stat[memory_pool_name] = data = {
+            used: info[0],
+            committed: info[1],
+            init: info[2],
+            max: info[3],
+            peak_used: info[4],
+            peak_committed: info[5],
+            peak_init: info[6],
+            peak_max: info[7],
+            last_used: info[8],
+            last_committed: info[9],
+            last_init: info[10],
+            last_max: info[11],
+          }
+
+          # Calculate stats across memory pools for peak_/last_ (we already know the values for current usage)
+          data.each_pair do |k,v|
+            stat[k] += v if k.start_with?('peak_', 'last_')
+          end
         end
       end
     end
 
-    return stat unless option
-
-    if stat[option]
-      stat[option]
+    if key
+      stat[key]
     else
-      0
+      stat
     end
   end