tlsf

Two-Level Segregated Fit memory allocator implementation. Written by Matthew Conte (matt@baisoku.org). Released under the BSD license.

Features

• O(1) cost for malloc, free, realloc, memalign
• Extremely low overhead per allocation (4 bytes)
• Low overhead per TLSF management of pools (~3kB)
• Low fragmentation
• Compiles to only a few kB of code and data
• Support for adding and removing memory pool regions on the fly

Caveats

• Currently, assumes architecture can make 4-byte aligned accesses
• Not designed to be thread safe; the user must provide this

Notes

This code was based on the TLSF 1.4 spec and documentation found at:

http://www.gii.upv.es/tlsf/main/docs

It also leverages the TLSF 2.0 improvement to shrink the per-block overhead from 8 to 4 bytes.

History

2016/04/10 - v3.1

• Code moved to github
• tlsfbits.h rolled into tlsf.c
• License changed to BSD

2014/02/08 - v3.0

• This version is based on improvements from 3DInteractive GmbH
• Interface changed to allow more than one memory pool
• Separated pool handling from control structure (adding, removing, debugging)
• Control structure and pools can still be constructed in the same memory block
• Memory blocks for control structure and pools are checked for alignment
• Added functions to retrieve control structure size, alignment size, min and max block size, overhead of pool structure, and overhead of a single allocation
• Minimal Pool size is tlsf_block_size_min() + tlsf_pool_overhead()
• Pool must be empty when it is removed, in order to allow O(1) removal

2011/10/20 - v2.0

• 64-bit support
• More compiler intrinsics for ffs/fls
• ffs/fls verification during TLSF creation in debug builds

2008/04/04 - v1.9

• Add tlsf_heap_check, a heap integrity check
• Support a predefined tlsf_assert macro
• Fix realloc case where block should shrink; if adjacent block is in use, execution would go down the slow path

2007/02/08 - v1.8

• Fix for unnecessary reallocation in tlsf_realloc

2007/02/03 - v1.7

• tlsf_heap_walk takes a callback
• tlsf_realloc now returns NULL on failure
• tlsf_memalign optimization for 4-byte alignment
• Usage of size_t where appropriate

2006/11/21 - v1.6

• ffs/fls broken out into tlsfbits.h
• tlsf_overhead queries per-pool overhead

2006/11/07 - v1.5

• Smart realloc implementation
• Smart memalign implementation

2006/10/11 - v1.4

• Add some ffs/fls implementations
• Minor code footprint reduction

2006/09/14 - v1.3

• Profiling indicates heavy use of blocks of size 1-128, so implement small block handling
• Reduce pool overhead by about 1kb
• Reduce minimum block size from 32 to 12 bytes
• Realloc bug fix

2006/09/09 - v1.2

• Add tlsf_block_size
• Static assertion mechanism for invariants
• Minor bugfixes

2006/09/01 - v1.1

• Add tlsf_realloc
• Add tlsf_walk_heap

2006/08/25 - v1.0

• First release