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base_block_alloc() grows new base blocks along the page size-class series to reduce the number of disjoint VM ranges. This works well when new base blocks are rare. Under high thread churn, many threads can miss the base free pool in parallel while allocating metadata. base_extent_alloc() drops base->mtx after mapping a new block, but before splitting and inserting the rest into the reuse pool. Therefore, each parallel miss can map its own block and each completed allocation then advances base->pind_last. The result is that small metadata requests can drive the growth heuristic to increasingly large mmap() sizes, far beyond the actual allocation demand. Cap the heuristic growth size at 128 MiB. This preserves the usual amortization benefit while bounding the rare pathological case where parallel misses rapidly advance the growth series. Large individual requests are still honored because min_block_size continues to override the cap.
jemalloc is a general purpose malloc(3) implementation that emphasizes fragmentation avoidance and scalable concurrency support. jemalloc first came into use as the FreeBSD libc allocator in 2005, and since then it has found its way into numerous applications that rely on its predictable behavior. In 2010 jemalloc development efforts broadened to include developer support features such as heap profiling and extensive monitoring/tuning hooks. Modern jemalloc releases continue to be integrated back into FreeBSD, and therefore versatility remains critical. Ongoing development efforts trend toward making jemalloc among the best allocators for a broad range of demanding applications, and eliminating/mitigating weaknesses that have practical repercussions for real world applications. The COPYING file contains copyright and licensing information. The INSTALL file contains information on how to configure, build, and install jemalloc. The ChangeLog file contains a brief summary of changes for each release. URL: https://jemalloc.net/