# Handling large message load This section provides tips on optimizing the performance of `syslog-ng`. Optimizing the performance is important for AxoSyslog hosts that handle large traffic. * Disable DNS resolution, or resolve hostnames locally. For details, see [Using name resolution in syslog-ng](../../docs/axosyslog-core/chapter-examples/examples-dns/index.md). * Enable flow-control for the TCP sources. For details, see [Managing incoming and outgoing messages with flow-control](../../docs/axosyslog-core/chapter-routing-filters/concepts-flow-control/index.md). * Do not use the `usertty()` destination driver. Under heavy load, the users are not be able to read the messages from the console, and it slows down `syslog-ng`. * Do not use regular expressions in our filters. Evaluating general regular expressions puts a high load on the CPU. Use simple filter functions and logical operators instead. For details, see [Regular expressions](../../docs/axosyslog-core/chapter-manipulating-messages/regular-expressions/index.md). * Warning When receiving messages using the UDP protocol, increase the size of the UDP receive buffer on the receiver host (that is, the AxoSyslog server or relay receiving the messages). Note that on certain platforms, for example, on Red Hat Enterprise Linux 5, even low message load (~200 messages per second) can result in message loss, unless the `so-rcvbuf()` option of the source is increased. In this cases, you will need to increase the `net.core.rmem_max` parameter of the host (for example, to `1024000`), but do not modify `net.core.rmem_default` parameter. As a general rule, increase the `so-rcvbuf()` so that the buffer size in kilobytes is higher than the rate of incoming messages per second. For example, to receive 2000 messages per second, set the `so-rcvbuf()` at least to `2 097 152` bytes. * Increase the value of the `flush-lines()` parameter. Increasing `flush-lines()` from `0` to `100` can increase the performance of AxoSyslog by 100%. Last modified June 27, 2023: [Update paths to follow-up moving the files (6585a5b1)]()