For Performance/slowness issues instead of taking Threaddump manually or instead of invoking PerformanceTool make use of the below URL when the issue occurs,

The above URL works even when the server is not responding.

Invoking the above URL collects the below outputs,

ThreadDump

RunningQueries

LockedQueries

ConnectionDump

at the time of the issue occurrence and automatically place it in the logs folder in the ServiceDeskPLus-MSP folder.

Once the above files are generated the below message will be shown in the browser,

Builds less than V9.4, zip log folder under ManageEngine/ServiceDeskPlus MSP/ server/default

This is applicable for Build from 9306.

P.S. If the performance issue is due to OutOfMemory error, then perform the usual debugging for out of memory like tuning java, getting HeapDump and analyzing the root cause.