They claim to perform well on at least some multi-thread workloads (read https://github.com/microsoft/mimalloc#performance https://github.com/microsoft/mimalloc

They claim to perform well on at least some multi-thread workloads (read https://github.com/microsoft/mimalloc#performance https://github.com/microsoft/mimalloc#performance): "The larson server workload allocates and frees objects between many threads. Larson and Krishnan [2] observe this behavior (which they call bleeding) in actual server applications, and the benchmark simulates this. Here, mimalloc is more than 2.5× faster than tcmalloc and jemalloc due to the object migration between different threads. This is a difficult benchmark for other allocators too where mimalloc is still 48% faster than the next fastest (snmalloc)."