zeropool 0.3.0

High-performance buffer pool with constant-time allocation, thread-safe operations, and 5x speedup over bytes crate
Documentation

ZeroPool

A high-performance, security-focused buffer pool for Rust

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Why ZeroPool?

ZeroPool is a thread-safe buffer pool that combines high performance with strong security guarantees. Unlike traditional buffer pools that trade security for speed, ZeroPool provides both:

  • Secure by default: All memory is automatically zeroed to prevent information leakage
  • Safe Rust: No unsafe memory operations, only safe abstractions
  • High performance: Thread-local caching and smart allocation strategies minimize overhead
  • Auto-configured: Adapts to your CPU topology for optimal multi-threaded performance

Perfect for applications that handle sensitive data (credentials, encryption keys, PII) while maintaining high throughput.

Quick Start

use zeropool::BufferPool;

let pool = BufferPool::new();

// Get a buffer (automatically zeroed and returned to pool when dropped)
let mut buffer = pool.get(1024 * 1024); // 1MB

// Use it for I/O or data processing
file.read(&mut buffer)?;

// Buffer automatically zeroed and returned to pool here

Key Features

Security First 🔒

  • Memory zeroing: All buffers are explicitly zeroed on allocation and return
  • No information leakage: Previous data never exposed to new allocations
  • Safe Rust: Zero unsafe memory operations (only safe Send/Sync trait impls)
  • Optional memory pinning: Prevent sensitive data from swapping to disk

High Performance ⚡

  • Thread-local caching: Lock-free fast path for 60-110ns allocation latency
  • Smart sharding: Minimal contention with power-of-2 shard count
  • Auto-configured: CPU-aware defaults (4-128 shards, 2-8 TLS cache size)
  • Configurable eviction: Choose between LIFO or CLOCK-Pro algorithms

Simple API 🎯

  • Just get() and drop(): Buffers automatically return to the pool
  • Builder pattern: Easy customization when needed
  • Type-safe: Leverages Rust's ownership for automatic resource management

Architecture

Thread 1     Thread 2     Thread N
┌─────────┐  ┌─────────┐  ┌─────────┐
│ TLS (4) │  │ TLS (4) │  │ TLS (4) │  ← Lock-free (60-110ns)
└────┬────┘  └────┬────┘  └────┬────┘
     └──────────┬─────────────┘
                ↓
       ┌────────────────┐
       │ Sharded Pool   │              ← Thread affinity
       │ [0][1]...[N]   │              ← Minimal contention
       └────────────────┘

Fast path: Thread-local cache (lock-free, ~60-110ns) Slow path: Thread-affinity shard selection (better cache locality) Optimization: Power-of-2 shards enable bitwise AND instead of modulo

Performance

Cache Behavior Benchmarks

Pattern Metric Result
Ping-pong (LIFO) Time per operation 3.56 µs
Ping-pong (ClockPro) Time per operation 3.68 µs
Hot/cold buffers Time per operation 1.05 µs
Multi-size workload Time per operation 6.2 µs
TLS cache (2 bufs) Allocation latency 60.5 ns
TLS cache (4 bufs) Allocation latency 108 ns
TLS cache (8 bufs) Allocation latency 288 ns
Eviction pressure Time per operation 400 ns

Multi-threaded Scaling

Threads Time per 1000 ops Notes
1 44.7 µs Single-threaded baseline
4 141 µs Good scaling with TLS cache
8 282 µs Near-linear scaling
16 605 µs Still scales well at high concurrency

Performance Characteristics

  • Constant latency: 60-110ns for TLS cache hits regardless of buffer size
  • Secure by default: ~20-25% overhead vs unsafe implementations (acceptable trade-off)
  • Lock-free fast path: Thread-local cache eliminates contention
  • Scales linearly: Near-linear scaling up to 16+ threads

Run yourself:

cargo bench

Test System

  • CPU: Intel i9-10900K @ 3.7GHz (10 cores, 20 threads, 5.3GHz turbo)
  • RAM: 32GB DDR4
  • OS: Linux 6.17.0

Configuration

use zeropool::BufferPool;

let pool = BufferPool::builder()
    .tls_cache_size(8)               // Buffers per thread
    .min_buffer_size(512 * 1024)     // Keep buffers ≥ 512KB
    .max_buffers_per_shard(32)       // Max pooled buffers
    .num_shards(16)                  // Override auto-detection
    .build();

Defaults (auto-configured based on CPU count):

  • Shards: 4-128 (power-of-2, ~1 shard per 2 cores)
  • TLS cache: 2-8 buffers per thread
  • Min buffer size: 1MB
  • Max per shard: 16-64 buffers

Memory Pinning

Lock buffer memory in RAM to prevent swapping sensitive data:

use zeropool::BufferPool;

let pool = BufferPool::builder()
    .pinned_memory(true)
    .build();

Useful for high-performance computing, security-sensitive data, or real-time systems. May require elevated privileges on some systems. Falls back gracefully if pinning fails.

Eviction Policy

Choose between simple LIFO or intelligent CLOCK-Pro buffer eviction:

use zeropool::{BufferPool, EvictionPolicy};

let pool = BufferPool::builder()
    .eviction_policy(EvictionPolicy::ClockPro)  // Better cache locality (default)
    .build();

let pool_lifo = BufferPool::builder()
    .eviction_policy(EvictionPolicy::Lifo)     // Simple, lowest overhead
    .build();

CLOCK-Pro (default): Uses access counters to favor recently-used buffers, preventing cache thrashing in mixed-size workloads. ~8 bytes overhead per buffer.

LIFO: Simple last-in-first-out eviction. Minimal memory overhead, best for uniform buffer sizes.

How It Works

Thread-local caching (lock-free)

  • Lock-free access to recently used buffers
  • No atomic operations on fast path (60-110ns latency)
  • Zero cache-line bouncing

Thread-local shard affinity

  • Each thread consistently uses the same shard (cache locality)
  • shard = hash(thread_id) & (num_shards - 1) (no modulo)
  • Minimal lock contention + better CPU cache utilization
  • Auto-scales with CPU count

First-fit allocation

  • O(1) instead of O(n) best-fit
  • Perfect for predictable I/O buffer sizes

Secure memory zeroing

  • All buffers are zeroed on return using fill(0)
  • All buffers are zeroed on allocation using resize(size, 0)
  • Prevents information leakage between buffer users
  • Safe for security-sensitive workloads

Thread Safety

BufferPool is Clone and thread-safe:

let pool = BufferPool::new();

for _ in 0..4 {
    let pool = pool.clone();
    std::thread::spawn(move || {
        let buf = pool.get(1024);
        // Each thread gets its own TLS cache
        // Buffer automatically returned when dropped
    });
}

Safety and Security

ZeroPool prioritizes both safety and security:

Memory Zeroing

  • All buffers are explicitly zeroed when returned to the pool using fill(0)
  • All buffers are zeroed when allocated from the pool using resize(size, 0)
  • Prevents information leakage between different buffer users
  • Safe for processing sensitive data (credentials, encryption keys, PII)

Safe Rust

  • Uses only safe Rust operations for memory management
  • No unsafe set_len() calls or uninitialized memory
  • Send and Sync automatically derived (no unsafe trait implementations)
  • All safety guaranteed by Rust's type system

Security Best Practices

  • Defense-in-depth: Zeroing at both allocation and deallocation
  • Optional memory pinning: Prevent swapping sensitive data to disk
  • Auditable: Simple, safe code that's easy to review
  • Production-ready: Suitable for security-critical applications

Use Cases

Security-Sensitive Applications

  • Cryptographic operations: Handle keys and sensitive material safely
  • Authentication systems: Process credentials without leakage risk
  • PII processing: GDPR/HIPAA compliant data handling
  • Secure communications: Network buffers for encrypted protocols

High-Performance I/O

  • Async file loading: io_uring, tokio, async-std
  • Network servers: HTTP, gRPC, WebSocket servers
  • Data processing: ETL pipelines, log processing
  • LLM inference: Fast checkpoint loading

Real-World Example

Before ZeroPool, loading GPT-2 checkpoints took 200ms with 70% spent on buffer allocation. With ZeroPool: 53ms (3.8x faster) while maintaining security guarantees.

System Scaling

ZeroPool automatically adapts to your system:

System Cores TLS Cache Shards Buffers/Shard Total Capacity
Embedded 4 4 4 16 64 (~64MB)
Laptop 8 6 8 16 128 (~128MB)
Workstation 16 6 8 32 256 (~256MB)
Small Server 32 8 16 64 1024 (~1GB)
Large Server 64 8 32 64 2048 (~2GB)
Supercompute 128 8 64 64 4096 (~4GB)

Comparison with Alternatives

Feature ZeroPool bytes::BytesMut Lifeguard Sharded-Slab
Memory zeroing ✅ Always ❌ No ❌ No ❌ No
Safe Rust ✅ 100% ⚠️ Some unsafe ⚠️ Some unsafe ⚠️ Heavy unsafe
Thread-safe ✅ Yes ❌ No ⚠️ Limited ✅ Yes
Lock-free path ✅ TLS cache ❌ No ❌ No ⚠️ Partial
Auto-configured ✅ CPU-aware ❌ Manual ❌ Manual ❌ Manual
Security focus ✅ Primary ❌ No ❌ No ❌ No

ZeroPool is the only buffer pool designed for security-first applications while maintaining competitive performance.

License

Dual licensed under Apache-2.0 or MIT.

Contributing

PRs welcome! Please include benchmarks for performance changes and ensure all tests pass:

cargo test
cargo bench
cargo fmt
cargo clippy

Changelog

See CHANGELOG.md for version history.

Credits

Built with ❤️ for the Rust community. Inspired by the need for secure, high-performance buffer management in production systems.