Do not send pending writes to I/O threads while OOM

src/networking.c

@@ -2398,6 +2398,8 @@ int handleClientsWithPendingWrites(void) {
     listIter li;
     listNode *ln;
     listRewind(server.clients_pending_write, &li);
+    /* Don't try to send to I/O threads if we are OOM as we want to free the clients' COB as soon as possible. */
+    int try_send_to_io_threads = server.active_io_threads_num > 1 && !(server.maxmemory > 0 && zmalloc_used_memory() > server.maxmemory);
     while ((ln = listNext(&li))) {
         client *c = listNodeValue(ln);
         c->flag.pending_write = 0;
@@ -2413,8 +2415,7 @@ int handleClientsWithPendingWrites(void) {
         if (!clientHasPendingReplies(c)) continue;
 
         /* If we can send the client to the I/O thread, let it handle the write. */
-//        int oom = server.maxmemory > 0 && zmalloc_used_memory() > server.maxmemory;
-        if (trySendWriteToIOThreads(c) == C_OK) continue;
+        if (try_send_to_io_threads && trySendWriteToIOThreads(c) == C_OK) continue;
 
         /* We can't write to the client while IO operation is in progress. */
         if (c->io_write_state != CLIENT_IDLE || c->io_read_state != CLIENT_IDLE) continue;