Add mm/README.txt

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5140 42af7a65-404d-4744-a932-0658087f49c3

2 files changed, 76 insertions, 1 deletions

diff --git a/nuttx/mm/README.txt b/nuttx/mm/README.txt
new file mode 100644
index 000000000..b0b80deae
--- /dev/null
+++ b/nuttx/mm/README.txt
@@ -0,0 +1,71 @@
+mm/README.txt
+=============
+
+This directory contains the NuttX memory management logic.  This include:
+
+1) The standard memory management functions as prototyped in stdlib.h as
+   specified in the  Base definitions volume of IEEE Std 1003.1-2001.  This
+   include the files:
+
+   o Standard Interfaces: mm_malloc.c, mm_calloc.c, mm_realloc.c,
+       mm_memalign.c, mm_free.c
+   o Less-Standard Interfaces: mm_zalloc.c, mm_mallinfo.c
+   o Internal Implementation: mm_initialize.c mm_sem.c  mm_addfreechunk.c
+       mm_size2ndx.c mm_shrinkchunk.c, mm_internal.h
+   o Build and Configuration files: Kconfig, Makefile
+
+   Memory Models:
+
+   o Small Memory Model.  If the MCU supports only 16-bit data addressing
+     then the small memory model is automatically used.  The maximum size
+     of the heap is then 64K.  The small memory model can also be forced
+     MCUs with wider addressing by defining CONFIG_SMALL_MEMORY in the
+     NuttX configuration file.
+   o Large Memory Model.  Otherwise, the allocator uses a model that
+     supports a heap of up to 4G.
+
+   This implementation uses a variable length allocator with the following
+   properties:
+
+   o Overhead:  Either 8- or 4-bytes per allocation for large and small
+     models, respectively.
+   o Alignment:  All allocations are aligned to 8- or 4-bytes for large
+     and small models, respectively.
+
+2) Test Program.  There is also a host-best test program that can be
+   used to verify the memory manager.  These are the file:
+
+   Makefile.test, mm_test.c, and mm_environment.h.
+
+   Build instructions:
+
+   make -f Makefile.test
+
+   The executable will be built in the top-level directory as nuttx/mm_text
+   (or mm_test.exe under Cygwin).
+
+3) Granule Allocator.  A non-standard granule allocator is also available
+   in this directory  The granule allocator allocates memory in units
+   of a fixed sized block ("granule").  All memory is aligned to the size
+   of one granule.
+
+   The granule allocator interfaces are defined in nuttx/include/nuttx/gran.h.
+   The granule allocator consists of these files in this directory:
+
+     mm_gran.h, mm_granalloc.c, mm_grancritical.c, mm_granfree.c
+     mm_graninit.c
+
+   The granule allocator is not used anywhere within the base NuttX code
+   as of this writing.  The intent of the granule allocator is to provide
+   a tool to support platform-specific management of aligned DMA memory.
+
+   NOTE: Because each granule is aligned to the granule size and each
+   allocations is in units of the granule size, selection of the granule
+   size is important:  Larger granules will give better performance and
+   less overhead but more losses of memory due to alignment and quantization
+   waste.
+
+   The current implementation also restricts the maximum allocation size
+   to 32 granules.  That restriction could be eliminated with some
+   additional coding effort, but currently requires larger granule
+   sizes for larger allocations.
diff --git a/nuttx/mm/mm_environment.h b/nuttx/mm/mm_environment.h
index 70e611116..d28fbf1d7 100644
--- a/nuttx/mm/mm_environment.h
+++ b/nuttx/mm/mm_environment.h
@@ -105,12 +105,16 @@ extern void mm_addregion(FAR void *heapstart, size_t heapsize);
 
 /* Debug macros are always on */
 
-# define CONFIG_DEBUG
+# define CONFIG_DEBUG 1
 
 # undef mdbg
 # define mdbg(format, arg...) printf(format, ##arg)
 # undef mvdg
 # define mvdbg(format, arg...) printf(format, ##arg)
+# undef mlldbg
+# define mlldbg(format, arg...) printf(format, ##arg)
+# undef mllvdg
+# define mllvdbg(format, arg...) printf(format, ##arg)
 
 #else
 # define mm_errno get_errno()