TLSF Memory Storage allocator implementation. Version 2.4 Feb 2008 Authors: Miguel Masmano, Ismael Ripoll & Alfons Crespo. Copyright UPVLC, OCERA Consortium. TLSF is released in the GPL/LGPL licence. The exact terms of the licence are described in the COPYING file. This component provides basic memory allocation functions: malloc and free, as defined in the standard "C" library. This allocator was designed to provide real-time performance, that is: 1.- Bounded time malloc and free. 2.- Fast response time. 3.- Efficient memory management, that is low fragmentation. The worst response time for both malloc and free is O(1). How to use it: This code is prepared to be used as a stand-alone code that can be linked with a regular application or it can be compiled to be a Linux module (which required the BigPhysicalArea patch). Initially the module was designed to work jointly with RTLinux-GPL, but it can be used as a stand alone Linux module. When compiled as a regular linux process the API is: Initialisation and destruction functions ---------------------------------------- init_memory_pool may be called before any request or release call: - size_t init_memory_pool(size_t, void *); - void destroy_memory_pool(void *); Request and release functions ----------------------------- As can be seen, there are two functions for each traditional memory allocation function (malloc, free, realloc, and calloc). One with the prefix "tlsf_" and the other with the suffix "_ex". The versions with the prefix "tlsf_" provides the expected behaviour, that is, allocating/releasing memory from the default memory pool. The default memory pool is the last pool initialised by the init_memory_pool function. On the other hand, the functions with the prefix "_ex" enable the use of several memory pools. - void *tlsf_malloc(size_t); - void *malloc_ex(size_t, void *); - void tlsf_free(void *ptr); - void free_ex(void *, void *); - void *tlsf_realloc(void *ptr, size_t size); - void *realloc_ex(void *, size_t, void *); - void *tlsf_calloc(size_t nelem, size_t elem_size); - void *calloc_ex(size_t, size_t, void *); EXAMPLE OF USE: char memory_pool[1024*1024]; { ... init_memory_pool(1024*1024, memory_pool); ... ptr1=malloc_ex(100, memory_pool); ptr2=tlsf_malloc(100); // This function will use memory_pool ... tlsf_free(ptr2); free_ex(ptr1, memory_pool); } Growing the memory pool ----------------------- Starting from the version 2.4, the function add_new_area adds an memory area to an existing memory pool. - size_t add_new_area(void *, size_t, void *); This feature is pretty useful when an existing memory pool is running low and we want to add more free memory to it. EXAMPLE OF USE: char memory_pool[1024*1024]; char memory_pool2[1024*1024]; { ... init_memory_pool(1024*1024, memory_pool); ... ptr[0]=malloc_ex(1024*256 memory_pool); ptr[1]=malloc_ex(1024*512, memory_pool); add_new_area(memory_pool2, 1024*1024, memory_pool); // Now we have an extra free memory area of 1Mb // The next malloc may not fail ptr[2]=malloc_ex(1024*512, memory_pool); ... } SBRK and MMAP support --------------------- The version 2.4 can use the functions SBRK and MMAP to _automatically_ growing the memory pool, before running out of memory. So, when this feature is enabled, unless the operating system were out of memory, a malloc operation would not fail due to an "out-of-memory" error. To enable this support, compile tlsf.c with the FLAGS -DUSE_MMAP=1 or -DUSE_SBRK=1 depending on whether you want to use "mmap" or "sbrk" or both. ** By default (default Makefile) this feature is enabled. EXAMPLE OF USE: gcc -o tlsf.o -O2 -Wall -DUSE_MMAP=1 -DUSE_SBRK=1 --- If the sbrk/mmap support is enabled and we are _only_ going to use one memory pool, it is not necessary to call init_memory_pool EXAMPLE OF USE (with MMAP/SBRK support enabled): { ... ptr2=tlsf_malloc(100); // This function will use memory_pool ... tlsf_free(ptr2); } This work has been supported by the followin projects: EUROPEAN: IST-2001-35102(OCERA) http://www.ocera.org. SPANISH: TIN2005-08665-C3-03