April 16, 2026 by Phil Eaton
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jemalloc is an alternative malloc implementation built particularly for long-running, multi-threaded programs. It also has builtin tools for profiling memory and debugging memory leaks. The original author and biggest contributor, Jason Evans, released it around 2006 for FreeBSD (where it's still in use) and worked on it at Meta for a decade.
Alternative malloc implementations are popular because they are usually trivial to start using on Linux if the program uses the system malloc. Set LD_PRELOAD=/path/to/my_alt_malloc.so and you (might) get magical performance gains (lower memory usage, faster allocations, etc.) without editing a single line of code.
There are many to pick from. Google has tcmalloc. It was first released as part of gperftools which hit 1.0 in 2009, but tcmalloc development continued separately from gperftools and these improvements were only made public in 2020. Microsoft has mimalloc (1.0 in 2019) and snmalloc (actively developed but not yet 1.0).
It will take another article entirely to survey users of these malloc implementations. Back to jemalloc...
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About the author
Phil is the founder of The Consensus. Before this, he contributed to Postgres products at EnterpriseDB, cofounded and led marketing at TigerBeetle, and was an engineering manager at Oracle. He runs the Software Internals Discord, the Software Internals Email Book Club, and co-runs NYC Systems. @eatonphil
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