GC: change collection trigger (#108)

src/cpp/garbage-collector.cpp

@@ -7,10 +7,12 @@
 
 namespace effil {
 
+constexpr size_t MINIMUN_SIZE_LEFT = 100;
+
 GC::GC()
         : enabled_(true)
-        , lastCleanup_(0)
-        , step_(200) {}
+        , lastCleanup_(MINIMUN_SIZE_LEFT)
+        , step_(2.) {}
 
 // Here is the naive tri-color marking
 // garbage collecting algorithm implementation.
@@ -41,7 +43,7 @@ void GC::collect() {
     DEBUG << "Removing " << (objects_.size() - black.size()) << " out of " << objects_.size() << std::endl;
     objects_ = std::move(black);
 
-    lastCleanup_.store(0);
+    lastCleanup_.store(std::max(objects_.size(), MINIMUN_SIZE_LEFT));
 }
 
 size_t GC::count() const {
@@ -63,9 +65,13 @@ sol::table GC::exportAPI(sol::state_view& lua) {
     api["step"] = [](const sol::stack_object& newStep){
         auto previous = instance().step();
         if (newStep.valid()) {
-            REQUIRE(newStep.get_type() == sol::type::number) << "bad argument #1 to 'effil.gc.step' (number expected, got " << luaTypename(newStep) << ")";
-            REQUIRE(newStep.as<int>() >= 0) << "effil.gc.step: invalid capacity value = " << newStep.as<int>();
-            instance().step(newStep.as<size_t>());
+            REQUIRE(newStep.get_type() == sol::type::number)
+                    << "bad argument #1 to 'effil.gc.step' (number expected, got "
+                    << luaTypename(newStep) << ")";
+            REQUIRE(newStep.as<double>() > 1)
+                    << "effil.gc.step: invalid capacity value = "
+                    << newStep.as<double>();
+            instance().step(newStep.as<double>());
         }
         return previous;
     };

src/cpp/garbage-collector.h

@@ -17,7 +17,7 @@ public:
     // This method is used to create all managed objects.
     template <typename ViewType, typename... Args>
     ViewType create(Args&&... args) {
-        if (enabled_ && lastCleanup_.fetch_add(1) == step_)
+        if (enabled_ && count() >= step_ * lastCleanup_)
             collect();
 
         std::unique_ptr<ViewType> object(new ViewType(std::forward<Args>(args)...));
@@ -43,8 +43,8 @@ public:
 private:
     mutable std::mutex lock_;
     bool enabled_;
-    std::atomic<size_t> lastCleanup_;
-    size_t step_;
+    std::atomic<uint64_t> lastCleanup_;
+    double step_;
     std::unordered_map<GCHandle, std::unique_ptr<BaseGCObject>> objects_;
 
 private:
@@ -55,8 +55,8 @@ private:
     void collect();
     void pause() { enabled_ = false; }
     void resume() { enabled_ = true; }
-    size_t step() const { return step_; }
-    void step(size_t newStep) { step_ = newStep; }
+    double step() const { return step_; }
+    void step(double newStep) { step_ = newStep; }
     bool enabled() { return enabled_; }
     size_t count() const;
 };

tests/lua/gc.lua

@@ -55,3 +55,67 @@ test.gc.store_same_value = function()
     effil.gc.collect()
     c:pop()[1] = 0
 end
+
+local function create_fabric()
+    local f = { data = {} }
+
+    function f:create(num)
+        for i = 1, num do
+            table.insert(self.data, effil.table())
+        end
+    end
+
+    function f:remove(num)
+        for i = 1, num do
+            table.remove(self.data, 1)
+        end
+    end
+    return f
+end
+
+test.gc.check_iterative = function()
+    test.equal(gc.count(), 1)
+    local fabric = create_fabric()
+    test.equal(2, effil.gc.step())
+
+    fabric:create(199)
+    test.equal(gc.count(), 200)
+
+    fabric:remove(50)
+    collectgarbage()
+    test.equal(gc.count(), 200)
+
+    fabric:create(1) -- trigger GC
+    test.equal(gc.count(), 151)
+    fabric:remove(150)
+
+    fabric:create(149)
+    test.equal(gc.count(), 300)
+    collectgarbage()
+
+    fabric:create(1) -- trigger GC
+    test.equal(gc.count(), 151)
+end
+
+test.gc.check_step = function()
+    local fabric = create_fabric()
+    effil.gc.step(3)
+
+    fabric:create(299)
+    fabric:remove(100)
+    test.equal(gc.count(), 300)
+    collectgarbage()
+
+    fabric:create(1) -- trigger GC
+    test.equal(gc.count(), 201)
+
+    test.equal(3, effil.gc.step(2.5))
+
+    fabric:create(299)
+    fabric:remove(250)
+    test.equal(gc.count(), 500)
+    collectgarbage()
+
+    fabric:create(1) -- trigger GC
+    test.equal(gc.count(), 251)
+end