How to tune elasticsearch performance

I am using ES to ingest flow data from other application, but I found that the ES speed isn't high enough, so sometimes it would drop flow.
How can I change the setting of ES performance ?
I have seen the elasticsearch.yml, jvm.options and, but there seems no setting about ES performance.

Thanks a lot.

What does your collection pipeline look like? What does your Elasticsearch cluster look like, e.g. Elasticsearch version, number of nodes, number of CPU cores, type of storage and heap size?

ES version: 5.6.2
CPU:2 cores

thanks for your reply!

this is the command from the input application:
ntopng /c -F "es;ntopng;ntopng-%Y.%m.%d;;"

What does your collection pipeline look like? How have you determined that it is Elasticsearch, and not your collection pipeline, that is the bottleneck? How large are your documents?

I think it's the same thread as you already opened at

As it seems you already have another thread open, I suggest we continue the discussion there. Please do not open multiple threads for the same issue.

sorry for that

Please see Tuning the ES performance