hotpath - Rust Performance, CPU & Memory Profiler

hotpath-rs is an easy-to-configure Rust performance profiler that shows exactly where your code spends time, burns CPU, and allocates memory.

It helps you distinguish between functions that are slow because they wait on I/O and those that are CPU-intensive. Instrument functions, channels, futures, and streams to find bottlenecks and focus optimizations where they matter most. Get actionable insights into time, memory, and async data flow with minimal setup.

Try the TUI demo via SSH - no installation required:

ssh demo.hotpath.rs

Explore the full documentation at hotpath.rs. See CONTRIBUTING.md for development setup and guidelines.

You can use it to produce one-off performance (timing, memory or CPU) reports:

compare performance between different app versions:

or use the live TUI dashboard to monitor real-time performance metrics with debug info:

https://github.com/user-attachments/assets/2e890417-2b43-4b1b-8657-a5ef3b458153

Features

• Time, CPU & memory profiling - identify expensive functions and allocations.
• Async observability - futures, channels and streams.
• Concurrency metrics - Mutex/RwLock wait time and contention.
• Tokio runtime monitoring - workers, scheduling and queues.
• Live TUI dashboard & static reports - real-time or one-off analysis.
• CI regression detection - benchmark every PR automatically.
• MCP server for AI agents - query profiling data in real time.
• Zero cost when disabled - fully feature-gated.

Current roadmap

• hotpath::channel!/stream!/future! events batching
• hotpath::mutex!/rw_lock!
• hotpath::channel!(..., wrap = true)
• hotpath::channel! timing histogram
• Instrument AsyncRead/AsyncWrite and Read/Write wrappers
• hotpath::sql!(...)
• hotpath::http!(...)
• ENV['HOTPATH_DISABLE_TIMING']

Getting Started

Installation

Add to your Cargo.toml:

[dependencies]
hotpath = "0.18"

[features]
hotpath = ["hotpath/hotpath"]
hotpath-cpu = ["hotpath/hotpath-cpu"]
hotpath-alloc = ["hotpath/hotpath-alloc"]

This config ensures that the lib has no compile time or runtime overhead unless explicitly enabled via a hotpath feature. All the lib dependencies are optional (i.e. not compiled) and all macros are noop unless profiling is enabled.

Basic setup

You'll need only #[hotpath::main] and #[hotpath::measure] macros to get started:

#[hotpath::measure]
fn sync_function(sleep: u64) {
    std::thread::sleep(Duration::from_nanos(sleep));
    let vec1 = vec![1, 2, 3];
    std::hint::black_box(&vec1); // force mem allocation
}

#[hotpath::measure]
async fn async_function(sleep: u64) {
    tokio::time::sleep(Duration::from_nanos(sleep)).await;
}

// When using with tokio, place the #[tokio::main] first
#[tokio::main]
#[hotpath::main]
async fn main() {
    for i in 0..10000 {
        sync_function(i);
        async_function(i * 2).await;

        hotpath::measure_block!("custom_block", {
            std::thread::sleep(Duration::from_nanos(i * 3))
        });
    }
}

Now, run your program with hotpath (and optionally hotpath-alloc features):

cargo run --features='hotpath,hotpath-alloc'

On exit it will print a report with timings, memory allocations and thread usage metrics:

[hotpath] 1.20s | timing, alloc, threads

timing - Function execution time metrics.
+------------------------------+-------+----------+----------+----------+---------+
| Function                     | Calls | Avg      | P95      | Total    | % Total |
+------------------------------+-------+----------+----------+----------+---------+
| docs_example::main           | 1     | 1.20 s   | 1.20 s   | 1.20 s   | 100.00% |
+------------------------------+-------+----------+----------+----------+---------+
| docs_example::async_function | 1000  | 1.15 ms  | 1.20 ms  | 1.15 s   | 96.10%  |
+------------------------------+-------+----------+----------+----------+---------+
| custom_block                 | 1000  | 18.13 µs | 31.71 µs | 18.13 ms | 1.51%   |
+------------------------------+-------+----------+----------+----------+---------+
| docs_example::sync_function  | 1000  | 16.58 µs | 27.63 µs | 16.58 ms | 1.38%   |
+------------------------------+-------+----------+----------+----------+---------+

alloc - Cumulative allocations during each function call (including nested calls).
+------------------------------+-------+---------+---------+---------+---------+
| Function                     | Calls | Avg     | P95     | Total   | % Total |
+------------------------------+-------+---------+---------+---------+---------+
| docs_example::main           | 1     | 63.0 KB | 63.1 KB | 63.0 KB | 100.00% |
+------------------------------+-------+---------+---------+---------+---------+
| docs_example::sync_function  | 1000  | 12 B    | 12 B    | 11.7 KB | 18.58%  |
+------------------------------+-------+---------+---------+---------+---------+
| custom_block                 | 1000  | 0 B     | 0 B     | 0 B     | 0.00%   |
+------------------------------+-------+---------+---------+---------+---------+
| docs_example::async_function | 1000  | 0 B     | 0 B     | 0 B     | 0.00%   |
+------------------------------+-------+---------+---------+---------+---------+

threads - Thread CPU and memory statistics. (RSS: 7.8 MB, Alloc: 2.1 MB, Dealloc: 304.3 KB, Diff: 1.8 MB, 5/10)
+--------------+----------+------+------+----------+---------+-----------+----------+----------+----------+
| Thread       | Status   | CPU% | Max% | CPU User | CPU Sys | CPU Total | Alloc    | Dealloc  | Diff     |
+--------------+----------+------+------+----------+---------+-----------+----------+----------+----------+
| hp-functions | Sleeping | 1.8% | 1.8% | 0.018s   | 0.001s  | 0.019s    | 1.8 MB   | 291.3 KB | 1.5 MB   |
+--------------+----------+------+------+----------+---------+-----------+----------+----------+----------+
| main         | Sleeping | 6.3% | 6.3% | 0.123s   | 0.070s  | 0.193s    | 367.8 KB | 9.9 KB   | 357.9 KB |
+--------------+----------+------+------+----------+---------+-----------+----------+----------+----------+
| hp-threads   | Running  | 0.0% | 0.0% | 0.000s   | 0.001s  | 0.001s    | 10.3 KB  | 3.0 KB   | 7.3 KB   |
+--------------+----------+------+------+----------+---------+-----------+----------+----------+----------+
| hp-server    | Sleeping | 0.0% | 0.0% | 0.000s   | 0.001s  | 0.001s    | 1.8 KB   | 56 B     | 1.7 KB   |
+--------------+----------+------+------+----------+---------+-----------+----------+----------+----------+
| thread_5     | Sleeping | -    | -    | 0.000s   | 0.000s  | 0.000s    | 640 B    | 24 B     | 616 B    |
+--------------+----------+------+------+----------+---------+-----------+----------+----------+----------+

Full documentation

See the full docs and advanced config tutorials at hotpath.rs.

• Sampling Comparison - when to use hotpath vs CPU sampling profilers
• Profiling modes - static reports vs live TUI dashboard
• Functions - measure execution time and memory allocations
• CPU profiling - attribute CPU samples to instrumented functions
• A/B Benchmarks - compare performance between app versions
• Async Data Flow - monitor channels, streams, and futures
• Debug & Metrics - track custom values with dbg!, val!, and gauge! macros
• Threads - monitor threads usage
• Tokio Runtime - monitor Tokio runtime worker stats and task scheduling
• MCP Server - LLM integration via Model Context Protocol
• GitHub CI - automated benchmarking and regression detection in CI
• Configuration - explore all config options

Waitlist

My long-term goal for hotpath-rs is to become the single place to understand all performance signals in a Rust application. From CPU and memory usage to locks, channels, and async execution, all the way up to SQL queries and HTTP/RPC calls.

I'm also building a hosted version that makes profiling reports easier to share, compare, and analyze across pull requests, deployments, and teams.

If that sounds useful, join the waitlist for early access:

https://hotpath.rs/#waitlist

Status

This project is under active development. Core public APIs are stable, but implementation details (JSON report formats, TUI/MCP internals, and advanced config options) may change between releases as the project evolves.