3fad1523c7
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@22528 a1c6a512-1295-4272-9138-f99709370657
163 lines
4.1 KiB
Text
163 lines
4.1 KiB
Text
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TLSF Memory Storage allocator implementation.
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Version 2.4 Feb 2008
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Authors: Miguel Masmano, Ismael Ripoll & Alfons Crespo.
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Copyright UPVLC, OCERA Consortium.
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TLSF is released in the GPL/LGPL licence. The exact terms of the licence
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are described in the COPYING file.
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This component provides basic memory allocation functions:
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malloc and free, as defined in the standard "C" library.
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This allocator was designed to provide real-time performance, that is:
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1.- Bounded time malloc and free.
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2.- Fast response time.
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3.- Efficient memory management, that is low fragmentation.
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The worst response time for both malloc and free is O(1).
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How to use it:
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This code is prepared to be used as a stand-alone code that can be
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linked with a regular application or it can be compiled to be a Linux
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module (which required the BigPhysicalArea patch). Initially the
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module was designed to work jointly with RTLinux-GPL, but it can be
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used as a stand alone Linux module.
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When compiled as a regular linux process the API is:
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Initialisation and destruction functions
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----------------------------------------
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init_memory_pool may be called before any request or release call:
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- size_t init_memory_pool(size_t, void *);
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- void destroy_memory_pool(void *);
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Request and release functions
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-----------------------------
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As can be seen, there are two functions for each traditional memory
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allocation function (malloc, free, realloc, and calloc). One with the
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prefix "tlsf_" and the other with the suffix "_ex".
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The versions with the prefix "tlsf_" provides the expected behaviour,
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that is, allocating/releasing memory from the default memory pool. The
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default memory pool is the last pool initialised by the
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init_memory_pool function.
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On the other hand, the functions with the prefix "_ex" enable the use of several memory pools.
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- void *tlsf_malloc(size_t);
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- void *malloc_ex(size_t, void *);
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- void tlsf_free(void *ptr);
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- void free_ex(void *, void *);
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- void *tlsf_realloc(void *ptr, size_t size);
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- void *realloc_ex(void *, size_t, void *);
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- void *tlsf_calloc(size_t nelem, size_t elem_size);
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- void *calloc_ex(size_t, size_t, void *);
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EXAMPLE OF USE:
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char memory_pool[1024*1024];
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{
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...
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init_memory_pool(1024*1024, memory_pool);
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...
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ptr1=malloc_ex(100, memory_pool);
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ptr2=tlsf_malloc(100); // This function will use memory_pool
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...
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tlsf_free(ptr2);
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free_ex(ptr1, memory_pool);
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}
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Growing the memory pool
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-----------------------
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Starting from the version 2.4, the function add_new_area adds an
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memory area to an existing memory pool.
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- size_t add_new_area(void *, size_t, void *);
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This feature is pretty useful when an existing memory pool is running
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low and we want to add more free memory to it.
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EXAMPLE OF USE:
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char memory_pool[1024*1024];
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char memory_pool2[1024*1024];
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{
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...
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init_memory_pool(1024*1024, memory_pool);
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...
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ptr[0]=malloc_ex(1024*256 memory_pool);
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ptr[1]=malloc_ex(1024*512, memory_pool);
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add_new_area(memory_pool2, 1024*1024, memory_pool);
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// Now we have an extra free memory area of 1Mb
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// The next malloc may not fail
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ptr[2]=malloc_ex(1024*512, memory_pool);
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...
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}
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SBRK and MMAP support
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---------------------
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The version 2.4 can use the functions SBRK and MMAP to _automatically_
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growing the memory pool, before running out of memory.
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So, when this feature is enabled, unless the operating system were out
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of memory, a malloc operation would not fail due to an "out-of-memory"
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error.
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To enable this support, compile tlsf.c with the FLAGS -DUSE_MMAP=1 or
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-DUSE_SBRK=1 depending on whether you want to use "mmap" or "sbrk" or both.
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** By default (default Makefile) this feature is enabled.
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EXAMPLE OF USE:
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gcc -o tlsf.o -O2 -Wall -DUSE_MMAP=1 -DUSE_SBRK=1
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---
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If the sbrk/mmap support is enabled and we are _only_ going to use one
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memory pool, it is not necessary to call init_memory_pool
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EXAMPLE OF USE (with MMAP/SBRK support enabled):
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{
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...
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ptr2=tlsf_malloc(100); // This function will use memory_pool
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...
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tlsf_free(ptr2);
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}
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This work has been supported by the followin projects:
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EUROPEAN: IST-2001-35102(OCERA) http://www.ocera.org.
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SPANISH: TIN2005-08665-C3-03
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