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Performance tips

Fluent Bit is designed for high performance and minimal resource usage. Depending on your use case, you can optimize further using specific configuration options to achieve faster performance or reduce resource consumption.

Reading files with tail

The Tail input plugin is used to read data from files on the filesystem. By default, it uses a small memory buffer of 32KB per monitored file. While this is sufficient for most generic use cases and helps keep memory usage low when monitoring many files, there are scenarios where you might want to increase performance by using more memory.

If your files are typically larger than 32KB, consider increasing the buffer size to speed up file reading. For example, you can experiment with a buffer size of 128KB:

pipeline:
  inputs:
    - name: tail
      path: '/var/log/containers/*.log'
      buffer_chunk_size: 128kb
      buffer_max_size: 128kb

By increasing the buffer size, Fluent Bit will make fewer system calls (read(2)) to read the data, reducing CPU usage and improving performance.

Fluent Bit and SIMD for JSON encoding

The release of Fluent Bit v4.1.0 introduced new performance improvements for JSON encoding using Single Instruction, Multiple Data (SIMD). Plugins that convert logs from the Fluent Bit internal binary representation to JSON can now do so 2.5 times (read) faster. Powered by the yyjson project.

Enabling SIMD support

Ensure that your Fluent Bit binary is built with SIMD support. This feature is available for architectures such as x86_64, amd64, aarch64, and arm64. As of now, SIMD is only enabled by default in Fluent Bit container images.

You can check if SIMD is enabled by looking for the following log entry when Fluent Bit starts:

[2024/11/10 22:25:53] [ info] [fluent bit] version=3.2.0, commit=12cb22e0e9, pid=74359
[2024/11/10 22:25:53] [ info] [storage] ver=1.5.2, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2024/11/10 22:25:53] [ info] [simd    ] SSE2
[2024/11/10 22:25:53] [ info] [cmetrics] version=0.9.8
[2024/11/10 22:25:53] [ info] [ctraces ] version=0.5.7
[2024/11/10 22:25:53] [ info] [sp] stream processor started

Look for the simd entry, which will indicate the SIMD support type, such as SSE2, NEON, or none.

If your Fluent Bit binary wasn't built with SIMD enabled, and you are using a supported platform, you can build Fluent Bit from source using the CMake option -DFLB_SIMD=On.

Run input plugins in threaded mode

By default, most input plugins run in the same system thread than the main event loop, however by configuration you can instruct them to run in a separate thread which will allow you to take advantage of other CPU cores in your system.

To run an input plugin in threaded mode, add threaded: true as in the following example:

pipeline:
  inputs:
    - name: tail
      path: '/var/log/containers/*.log'
      threaded: true