Fix issue where GC is not free'd until a BGSAVE

Former-commit-id: e19350005b571591876e49219bfca75e905604a5

src/server.cpp

@@ -2440,6 +2440,16 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
     /* CRON functions may trigger async writes, so do this last */
     ProcessPendingAsyncWrites();
 
+    run_with_period(10) {
+        // Server threads don't free the GC, but if we don't have a
+        //  a bgsave or some other async task then we'll hold onto the
+        //  data for too long
+        g_pserver->asyncworkqueue->AddWorkFunction([]{
+            auto epoch = g_pserver->garbageCollector.startEpoch();
+            g_pserver->garbageCollector.endEpoch(epoch);
+        });
+    }
+
     g_pserver->cronloops++;
     return 1000/g_pserver->hz;
 }