Document how to benchmark Dragonfly

docs/development/benchmarking.md

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+# Benchmarking
+
+Do you have an existing Redis environment and would like to see if Dragonfly could be a better
+replacement? <br/>
+Are you developing a service and would like to determine which cloud instance type to
+allocate for Dragonfly? <br/>
+Do you wonder how many replicas you need to support your workload?
+
+If so, read on, because this page is for you!
+
+## Squeezing the Best Performance
+
+A benchmark is done to assess the performance aspects of a system. In the case of Dragonfly, a
+benchmark is commonly used to assess the CPU and memory performance & utilization.
+
+Depending on the goals of your benchmark, you should choose the machine size accordingly. For a
+production mimicking benchmark, you should use a machine size and traffic load similar to that of
+your busiest production timing, or even higher to allow for some cushion.
+
+### `io_uring`
+
+Dragonfly supports both `epoll` and [`io_uring`](https://en.wikipedia.org/wiki/Io_uring) Linux APIs.
+`io_uring` is a newer API, which is faster. Dragonfly runs best with `io_uring`, but it is only
+available with Linux kernels >= 5.1.
+
+`io_uring` is available in Debian versions Bullseye (11) or later, Ubuntu 21.04 or later, Red Hat
+Enterprise Linux 9.3 or later, Fedora 37 or later.
+
+To find if your machine has `io_uring` support you could run the following:
+
+```shell
+grep io_uring_setup /proc/kallsyms
+```
+
+### Choosing Instance Type
+
+Cloud providers, such as Amazon AWS, provide different types and sizes of virtual machines. When in
+doubt, you could always opt in for a bigger instance (for both Dragonfly and the client to send the
+benchmarking traffic) so that you'll know what the upper limit is.
+
+### Choosing Thread Count
+
+By default, Dragonfly will create a thread for each available CPU on the machine. You can modify
+this behavior with the `--proactor_threads` flag. Generally you should not use this flag for a
+machine dedicated to running Dragonfly. You can specify a lower number if you only want Dragonfly to
+utilize some of the machine, but don't specify a higher number (i.e. more than CPUs) as it would
+degrade performance.
+
+## Setting Up Dragonfly
+
+Dragonfly can run in [Docker](/getting-started/docker) or directly installed as a
+[binary](/getting-started/binary) on your machine. See the [Getting Started](/getting-started) page
+for other options and the latest documentation.
+
+## Reducing Noise
+
+Ideally, a benchmark should be run in as similar as possible environment as the production setup.
+
+In busy production deployments, it is common to run Dragonfly in its own machine (virtual or
+dedicated). If you plan to do so in your production setup as well (which we highly recommend),
+consider running the benchmark in a similar way.
+
+In practice, it means that any other systems in your setup (like other services & databases) should
+run in other machines. Importantly, also **the software that sends the traffic should run in another
+machine.**
+
+## Sending Traffic
+
+If your service already has existing benchmarking tools, or ways to record and replay production
+traffic, you should definitely use them. That would be the closest estimation to what a real
+production deployment with a backing Dragonfly would look like.
+
+If, like many others, you do not (yet) have such a tool, you could either write your own tool to
+simulate production traffic or use an existing tool like `memtier_benchmark`.
+
+When writing your own tool, try to recreate the production traffic as closely as possible. Use the
+same commands (like `SET`, `GET`, `SADD`, etc), with the expected ratio between them, and the
+expected key and value sizes.
+
+If you choose to use an existing benchmarking tool, a popular and mature one is
+[`memtier_benchmark`](https://github.com/RedisLabs/memtier_benchmark). It's an Open Source tool for
+generic load generation and benchmarking with many features. We use it for benchmarking constantly.
+Check out their [documentation
+page](https://redis.com/blog/memtier_benchmark-a-high-throughput-benchmarking-tool-for-redis-memcached/)
+for more details, but as a quick reference you could use:
+
+```shell
+memtier_benchmark \
+    --server=<IP / Host> \
+    --threads=<thread count> \
+    --clients=<clients per thread> \
+    --requests=<requests per client>
+```
+
+## Having Troubles? Anything Unclear?
+
+Improving our documentation and helping the community is always of the higher priority for us, so
+please feel free to reach out!