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Add mm/README.txt
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5140 42af7a65-404d-4744-a932-0658087f49c3
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patacongo
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5 changed files with 84 additions and 3 deletions
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@ -3333,3 +3333,5 @@
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is not yet functional.
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* configs/stm3240g-eval/discover: A configuration for testing
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the UDP discovery utility. Contributed by Max Holtzberg.
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* mm/README.txt: Add a new README file.
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@ -8,7 +8,7 @@
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<tr align="center" bgcolor="#e4e4e4">
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<td>
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<h1><big><font color="#3c34ec"><i>NuttX README Files</i></font></big></h1>
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<p>Last Updated: August 1, 2012</p>
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<p>Last Updated: September 12, 2012</p>
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</td>
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</tr>
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</table>
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@ -237,6 +237,8 @@
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| | `- <a href="http://nuttx.svn.sourceforge.net/viewvc/nuttx/trunk/nuttx/lib/README.txt?view=log"><b><i>README.txt</i></b></a>
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| |- libxx/
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| | `- <a href="http://nuttx.svn.sourceforge.net/viewvc/nuttx/trunk/nuttx/libxx/README.txt?view=log"><b><i>README.txt</i></b></a>
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| |- mm/
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| | `- <a href="http://nuttx.svn.sourceforge.net/viewvc/nuttx/trunk/nuttx/mm/README.txt?view=log"><b><i>README.txt</i></b></a>
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| |- syscall/
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| | `- <a href="http://nuttx.svn.sourceforge.net/viewvc/nuttx/trunk/nuttx/syscall/README.txt?view=log"><b><i>README.txt</i></b></a>
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| `- tools/
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@ -806,6 +806,8 @@ nuttx
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| `- README.txt
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|- libxx/
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| `- README.txt
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|- mm/
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| `- README.txt
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|- syscall/
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| `- README.txt
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`- tools/
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71
mm/README.txt
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71
mm/README.txt
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mm/README.txt
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=============
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This directory contains the NuttX memory management logic. This include:
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1) The standard memory management functions as prototyped in stdlib.h as
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specified in the Base definitions volume of IEEE Std 1003.1-2001. This
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include the files:
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o Standard Interfaces: mm_malloc.c, mm_calloc.c, mm_realloc.c,
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mm_memalign.c, mm_free.c
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o Less-Standard Interfaces: mm_zalloc.c, mm_mallinfo.c
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o Internal Implementation: mm_initialize.c mm_sem.c mm_addfreechunk.c
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mm_size2ndx.c mm_shrinkchunk.c, mm_internal.h
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o Build and Configuration files: Kconfig, Makefile
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Memory Models:
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o Small Memory Model. If the MCU supports only 16-bit data addressing
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then the small memory model is automatically used. The maximum size
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of the heap is then 64K. The small memory model can also be forced
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MCUs with wider addressing by defining CONFIG_SMALL_MEMORY in the
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NuttX configuration file.
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o Large Memory Model. Otherwise, the allocator uses a model that
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supports a heap of up to 4G.
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This implementation uses a variable length allocator with the following
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properties:
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o Overhead: Either 8- or 4-bytes per allocation for large and small
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models, respectively.
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o Alignment: All allocations are aligned to 8- or 4-bytes for large
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and small models, respectively.
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2) Test Program. There is also a host-best test program that can be
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used to verify the memory manager. These are the file:
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Makefile.test, mm_test.c, and mm_environment.h.
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Build instructions:
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make -f Makefile.test
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The executable will be built in the top-level directory as nuttx/mm_text
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(or mm_test.exe under Cygwin).
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3) Granule Allocator. A non-standard granule allocator is also available
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in this directory The granule allocator allocates memory in units
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of a fixed sized block ("granule"). All memory is aligned to the size
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of one granule.
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The granule allocator interfaces are defined in nuttx/include/nuttx/gran.h.
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The granule allocator consists of these files in this directory:
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mm_gran.h, mm_granalloc.c, mm_grancritical.c, mm_granfree.c
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mm_graninit.c
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The granule allocator is not used anywhere within the base NuttX code
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as of this writing. The intent of the granule allocator is to provide
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a tool to support platform-specific management of aligned DMA memory.
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NOTE: Because each granule is aligned to the granule size and each
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allocations is in units of the granule size, selection of the granule
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size is important: Larger granules will give better performance and
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less overhead but more losses of memory due to alignment and quantization
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waste.
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The current implementation also restricts the maximum allocation size
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to 32 granules. That restriction could be eliminated with some
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additional coding effort, but currently requires larger granule
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sizes for larger allocations.
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@ -105,12 +105,16 @@ extern void mm_addregion(FAR void *heapstart, size_t heapsize);
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/* Debug macros are always on */
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# define CONFIG_DEBUG
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# define CONFIG_DEBUG 1
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# undef mdbg
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# define mdbg(format, arg...) printf(format, ##arg)
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# undef mvdg
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# define mvdbg(format, arg...) printf(format, ##arg)
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# undef mlldbg
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# define mlldbg(format, arg...) printf(format, ##arg)
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# undef mllvdg
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# define mllvdbg(format, arg...) printf(format, ##arg)
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#else
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# define mm_errno get_errno()
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