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dendrite/docs/installation/11_optimisation.md
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Optimise your installation Installation true 11 /installation/start/optimisation

Optimise your installation

Now that you have Dendrite running, the following tweaks will improve the reliability and performance of your installation.

File descriptor limit

Most platforms have a limit on how many file descriptors a single process can open. All connections made by Dendrite consume file descriptors — this includes database connections and network requests to remote homeservers. When participating in large federated rooms where Dendrite must talk to many remote servers, it is often very easy to exhaust default limits which are quite low.

We currently recommend setting the file descriptor limit to 65535 to avoid such issues. Dendrite will log immediately after startup if the file descriptor limit is too low:

level=warning msg="IMPORTANT: Process file descriptor limit is currently 1024, it is recommended to raise the limit for Dendrite to at least 65535 to avoid issues"

UNIX systems have two limits: a hard limit and a soft limit. You can view the soft limit by running ulimit -Sn and the hard limit with ulimit -Hn:

$ ulimit -Hn
1048576

$ ulimit -Sn
1024

Increase the soft limit before starting Dendrite:

ulimit -Sn 65535

The log line at startup should no longer appear if the limit is sufficient.

If you are running under a systemd service, you can instead add LimitNOFILE=65535 option to the [Service] section of your service unit file.

DNS caching

Dendrite has a built-in DNS cache which significantly reduces the load that Dendrite will place on your DNS resolver. This may also speed up outbound federation.

Consider enabling the DNS cache by modifying the global section of your configuration file:

  dns_cache:
    enabled: true
    cache_size: 4096
    cache_lifetime: 600s

Time synchronisation

Matrix relies heavily on TLS which requires the system time to be correct. If the clock drifts then you may find that federation no works reliably (or at all) and clients may struggle to connect to your Dendrite server.

Ensure that the time is synchronised on your system by enabling NTP sync.