tikv-jemallocator

tikv-jemallocator is the maintained Rust wrapper for jemalloc, providing the most stable allocation latency across all size classes and thread counts. It includes built-in heap profiling via tikv-jemalloc-ctl. The underlying jemalloc allocator delivers approximately 30% higher throughput at high contention vs system malloc, and its xallocx API is the user-space counterpart to mremap — letting containers like folly-fbvector grow in place without copying. tikv-jemallocator inherits these capabilities transparently for any Rust Vec<T> since Vec's reallocation goes through the global allocator's grow path.

When to choose jemalloc

jemalloc is the better choice for servers with mixed allocation sizes — its arena-based design handles the full spectrum from tiny allocations to large mmap'd regions with consistent latency. The built-in profiling (tikv-jemalloc-ctl) lets you inspect heap state without external tools. For long-running workloads where fragmentation accumulates, jemalloc's resistance is materially better than glibc's.

For cross-platform builds or workloads dominated by small allocations (<= 4 KB), mimalloc may be faster. On musl targets, either is nearly mandatory. See rust-memory-allocators for the full picture and fastest-dynamic-arrays for why the allocator choice often matters more than the container choice.