Bgdrop

A minimal background dropper for Rust. Free memory in background threads to reduce latency spikes by 100 times.

---- tests::benchmark stdout ----
Duration without background drop: 27.3477ms
Duration with background drop: 108.5µs
Duration with background drop and threads: 105.2µs
Speedup with background drop: 252.05x
Speedup with background drop and threads: 259.96x

Test results by releasing 1000 trees of 1000 nodes each.

📦 Installation

• Edit Cargo.toml

# Cargo.toml
[dependencies]
bgdrop = "0.1"

• Or use Cargo

cargo add bgdrop

🔧 Usage

use bgdrop::Bgdrop;

fn main() {
    // Create a background dropper with 1 thread
    let dropper = Bgdrop::new();

    // Drop a large Vec in the background
    let large_vec = vec![0u8; 10_000_000];
    dropper.drop(large_vec);

    // Create a background dropper with multiple threads
    let pool = Bgdrop::with_threads(4);
    for _ in 0..10 {
        pool.drop(vec![0u8; 1_000_000]);
    }
}

⚠️ Notice

• Creating a Bgdrop instance will start at least one dedicated background thread for memory dropping.
• Avoid creating Bgdrop instances frequently. Use .clone() to share the same background thread.
• For large or complex data structures (e.g., Vec<Vec<_>>, HashMap<_, _>, or trees), offloading the drop to background can improve performance by 10× or more, especially in latency-critical code paths.
• For small types like tiny Vecs, primitive types, or types that do not implement Clone, bgdrop is unnecessary and adds overhead.
• Use bgdrop only when dropping time becomes a measurable bottleneck.

💡 Motivation

In performance-sensitive applications like games, real-time systems, or low-latency services, releasing large memory allocations (e.g. Vec<u8>, HashMap, etc.) may cause noticeable spikes in frame time or latency.

By moving the drop operation to a background thread, bgdrop helps smooth the performance curve.

🔒 Thread Safety

All types submitted to drop() must be:

• Send
• 'static lifetime

Internally, values are wrapped in Box<dyn Send> and sent via a lock-free crossbeam::channel to a background thread that performs the drop.

🚧 Limitations

• !Sync types cannot be used.
• Type erasure using Box<dyn Send> incurs a minor allocation cost.
• Dropped objects' destructors cannot observe ordering with respect to other code.

📜 License

MIT