Handle the performance issue

I am using Dremio version 20. Users report Dremio has slow performance even login. It took around 4-5 seconds. Try to identify the heavy loading queries or change the
DREMIO_MAX_DIRECT_MEMORY_SIZE_MB to 65535 in each executors but no luck. How can I do to identify the cause of issue? Any best practices can analyze the Dremio performance issue.

@Ming Login slowness is on the coordinator, I assume you are on community edition. Have run a thread dump on the coordinator during the time taken to login and see what is going on