PersistentValueStorage: remember last free page instead of reshuffling

This unifies the operation when the gc is running with the normal mode,
avoiding a potentially costly iteration over all pages for allocations
during an ongoing gc cycle.

Change-Id: I39e8990c303149e3bc458b10522cc1487e62a401
Reviewed-by: Olivier De Cannière <olivier.decanniere@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/qml/jsruntime/qv4persistent_p.h b/src/qml/jsruntime/qv4persistent_p.h
index 7e208bd4fd..c24d337b60 100644
--- a/src/qml/jsruntime/qv4persistent_p.h
+++ b/src/qml/jsruntime/qv4persistent_p.h
@@ -51,10 +51,13 @@ struct Q_QML_EXPORT PersistentValueStorage
     Iterator begin() { return Iterator(firstPage, 0); }
     Iterator end() { return Iterator(nullptr, 0); }
 
+    void clearFreePageHint();
+
     static ExecutionEngine *getEngine(const Value *v);
 
     ExecutionEngine *engine;
     void *firstPage;
+    void *freePageHint = nullptr;
 private:
     static void freeUnchecked(Value *v);
     static void freePage(void *page);