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Memory Allocator Optimization

1 post · Mar 2026

What this trail covers

Meilisearch has undergone significant memory allocator optimization, moving from mimalloc v2 to mimalloc v3 and investigating the interaction with LMDB. This has resulted in reduced memory usage and improved performance, particularly on network-attached storage. The investigation revealed issues with allocator cooperation between Meilisearch and LMDB, leading to memory bloat. Unifying the allocator (mimalloc v3) resolved these issues and improved performance.

All Meilisearch trails
  1. The good, the bad, and the leaky: jemalloc, bumpalo, and mimalloc in MeilisearchThis post details the investigation and resolution of a memory leak and high memory usage in Meilisearch. It covers the challenges of debugging memory issues in Rust, the use of jemalloc for profiling, the identification of a leak related to bumpalo's `into_bump_slice` and storing `std::Vec` within it, and the critical discovery that LMDB's default allocator was not cooperating with Meilisearch's custom allocator (mimalloc v2). The solution involved unifying the allocator to mimalloc v3, which significantly reduced memory usage and improved performance, especially on network-attached storage. Benchmarks showed performance gains and losses, highlighting tradeoffs.