Poor performance Elasticsearch

Hi, I'm having problem with my elasticsearch running server. At the beginning it was working fine, when I needed to update Data. But suddenly after trying to update several files at once (5 files), the system is performing poorly, taking more than 7 or 8 hours to process a file, when previously is was 1 hour. Also, the performance problem has reached Kibana (it takes 2 minutes to load the main page with date and previously it was less than a second). I think the problem is because of the heap ( which is configured as -Xms2g -Xmx8g) and, for example, Kibana is using 99%. I tried to delete all the indices from the node and the problem persist.
I tried to set up bootstrap.mlockall: true, but the server that's allow it (Unable to lock JVM Memory: error=12,reason=Cannot allocate memory).
The server has 8GB of RAM.

This is the current status of the health state cluster:
{
"cluster_name" : "elasticsearch",
"status" : "green",
"timed_out" : false,
"number_of_nodes" : 1,
"number_of_data_nodes" : 1,
"active_primary_shards" : 6,
"active_shards" : 6,
"relocating_shards" : 0,
"initializing_shards" : 0,
"unassigned_shards" : 0,
"delayed_unassigned_shards" : 0,
"number_of_pending_tasks" : 0,
"number_of_in_flight_fetch" : 0,
"task_max_waiting_in_queue_millis" : 0,
"active_shards_percent_as_number" : 100.0
}

You should follow these guidelines when setting the heap size.

Before posting this, the heap size was set up 2GB min and 8 GB max. Now I've changed it according to your link with 4GB max, but the performance is the same.

What kind of storage do you have? What does disk I/O and iowait look like when you are updating? How are you performing the updates?

right now the performance when executing filebeat is:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND

root 20 0 4604800 476744 18296 S 148.5 5.8 3:01.82 java

elastic+ 20 0 8042688 687640 19948 S 48.5 8.4 1:18.83. java

root 20 0 379012 27884 8644 S 30.9 0.3 0:15.81 filebeat

Can you run iostat -x while the update is going on?

What type of disk do you have?

How are you performing the updates?