Are you using the file inputs? It is not clear, if besides the gelf input you are also reading files using the file input, then you should evaluate everything.
Can you provide more context?
Also, any reason to set the pipeline.batch.delay to 1 second? This setting rarely needs to be changed.
I do not use docker, but can you not disable the swap for the logstash container? Will it get OOM errors if you disable it?