world loading memory pressure detector

Signed-off-by: Pavel Okhlopkov <pavel.okhlopkov@flant.com>

src/core/memory_monitor.cpp

@@ -126,5 +126,12 @@ bool MemoryMonitor::isMemoryPressure() const {
     return available < (totalRAM_ * 10 / 100);
 }
 
+bool MemoryMonitor::isSevereMemoryPressure() const {
+    size_t available = getAvailableRAM();
+    // Severe pressure if < 15% RAM available — background workers should
+    // pause entirely to avoid OOM-killing other applications.
+    return available < (totalRAM_ * 15 / 100);
+}
+
 } // namespace core
 } // namespace wowee

src/rendering/terrain_manager.cpp

@@ -1212,6 +1212,28 @@ void TerrainManager::workerLoop() {
                 break;
             }
 
+            // --- Memory-aware throttling ---
+            // Back-pressure: if the ready queue is deep (finalization can't
+            // keep up), or the system is running low on RAM, sleep instead
+            // of pulling more tiles.  Each prepared tile can hold hundreds
+            // of MB of decoded textures; limiting concurrency here prevents
+            // WoWee from consuming all system memory during world load.
+            const auto& memMon = core::MemoryMonitor::getInstance();
+            if (memMon.isSevereMemoryPressure()) {
+                // Severe pressure — don't pull ANY work until main thread
+                // finalizes tiles and frees decoded texture data.
+                lock.unlock();
+                std::this_thread::sleep_for(std::chrono::milliseconds(200));
+                continue;
+            }
+            if (readyQueue.size() >= maxReadyQueueSize_ || memMon.isMemoryPressure()) {
+                // Moderate pressure or ready queue is backing up — sleep briefly
+                // to let the main thread catch up with finalization.
+                lock.unlock();
+                std::this_thread::sleep_for(std::chrono::milliseconds(50));
+                continue;
+            }
+
             if (!loadQueue.empty()) {
                 coord = loadQueue.front();
                 loadQueue.pop_front();