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

Signed-off-by: Uri Yagelnik <uriy@amazon.com>

src/networking.c

@@ -2397,6 +2397,8 @@ int handleClientsWithPendingWrites(void) {
     listIter li;
     listNode *ln;
     listRewind(server.clients_pending_write, &li);
+    /* Avoid sending to I/O threads during out-of-memory conditions to free clients' COBs as quickly as possible */
+    int try_send_to_io_threads = server.active_io_threads_num > 1 && getMaxmemoryState(NULL, NULL, NULL, NULL) == C_OK;
     while ((ln = listNext(&li))) {
         client *c = listNodeValue(ln);
         c->flag.pending_write = 0;
@@ -2412,7 +2414,7 @@ int handleClientsWithPendingWrites(void) {
         if (!clientHasPendingReplies(c)) continue;
 
         /* If we can send the client to the I/O thread, let it handle the write. */
-        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;