Changes between Initial Version and Version 1 of kernel_pmem

Timestamp:

Oct 5, 2014, 1:18:29 PM (11 years ago)

Author:

alain

Comment:

--

kernel_pmem

@@ +1 @@
+= Physical Memory Allocators ==
+
+The [source:soft/giet_vm/giet_common/pmem.c pmem.c] and [source:soft/giet_vm/giet_common/pmem.h pmem.h] files define the data structures and functions used by the boot-loader to allocate physical memory. 
+
+The physical memory allocation is statically done by the boot-loader, and the functions defined here
+should not be used by the kernel.
+
+The physical address format is 40 bits, structured in five fields:
+| 4 | 4 |  11  |  9   |   12   |
+| X | Y | BPPI | SPPI | OFFSET |
+ * The (X,Y) fields define the cluster coordinates in the 2D mesh.
+ * The BPPI field is the Big Physical Page Index
+ * The SPPI field is the Small Physical Page Index
+ * The |X|Y|BPPI|SPPI| concatenation is the PPN (Physical Page Number)
+
+As the physical memory can be distributed in all clusters, there is one physical memory allocator in each cluster, and the allocation state is defined by the boot_pmem_alloc[x][y] array (defined in the
+boot.c file). As the allocated physical memory is never released, the allocator structure is very simple, and is defined in the pmem_alloc_t structure.
+
+As the boot-loader is executed by one single processor, this structure does not contain any lock protecting exclusive access.
+
+Both small pages allocator and big pages allocators allocate a variable number of CONTIGUOUS pages in the physical space. The first big page in cluster[0][0] is reserved for identity mapping vsegs, and is not allocated by the physical memory allocators.
+
+
+=== void _pmem_alloc_init( unsigned int x, unsigned int y, unsigned int base, unsigned int size ) ===
+
+This function initialises the physical memory allocator in cluster (x,y).
+The pseg base address and the pseg size must be multiple of 2 Mbytes (one big page).
+ * base is the pseg local base address (no cluster extension)
+ * size is the pseg length (bytes)
+The first page in cluster[0][0] is reserved for the boot code identity mapping vsegs.
+
+=== unsigned int _get_small_ppn( pmem_alloc_t* p, unsigned int  n ) ===
+
+This function allocates n contiguous small pages (4 Kbytes), 
+from the physical memory allocator defined by the p pointer. 
+It returns the PPN (28 bits) of the first physical small page. 
+Exit if not enough free space.
+
+=== unsigned int _get_big_ppn( pmem_alloc_t* p, unsigned int  n ) ===
+
+This function allocates n contiguous big pages (2 Mbytes), 
+from the physical memory allocator defined by the p pointer. 
+It returns the PPN (28 bits) of the first physical big page (the SPPI field of the ppn is always 0). 
+Exit if not enough free space.
+
+