Sampler is a performance analysis tool to investigate any slowdown or related issue for both client and server.

Until further documentation or the GUI are done the target audience is mostly advanced users or anyone asked to provide debugging data by mod or mod pack authors.

Its most important features are:

A sampling profiler (sampler) to see exactly where the Minecraft client/server spends its time: start, (wait), stop, export sub-commands
Event-based sampling triggers, e.g. to capture only lag spikes: trigger sub-command
Actually precise tickrate information: tps sub-command or F3
Counts for ticking game objects to notice any excess: counts sub-command, more detailed when invoked with the dimension id
Memory information and garbage collection statistics: memory sub-command
Highlights for tile entity special renderers (potentially expensively rendered blocks): tesr sub-command
Highlights for the sources of chunk updates: renderupdates sub-command
Various other sub-commands for investigating network I/O, chunk loads, saves, finding blocks/entities, ...

This mod is designed to have no observable overhead while idle and very little overhead during profiling. Its feature set is extensive and best explored using its help functionality.

The user interface is purely command driven at this point, see

/sampler help

for all server-side commands and

/csampler help

for all client-side commands.

Every command is following the pattern /sampler <subcommand> [<arguments>...] for the server side and /csampler <subcommand> [<arguments>...] for the client side. Detailed help for each sub-command is available through /(c)sampler help <subcommand>.

(The logo is a chart from an analysis frontend that is still under development and not publicly available at this time)