[PATCH 0/5] Optimize workspace/malloc initialization

[Sebastian Huber]

Hello Karel,

On 30/11/2021 12:04, Karel Gardas wrote:
> just a question. Do you plan to preserve functionality of _Heap_Extend()
> in the future? 

this feature is still available. However, there was a significant change 
in the handling of BSP-provided memory areas between RTEMS 5 and 6.

> Asking since I'm using it for amd64/uefi bsp. During the
> bsp start I get efi services pointers and use that to traverse memory
> map. Based on available free blocks I try to allocate memory using EFI
> API and if successful I'm calling _Heap_Extend with it to pass ram to
> RTEMS. That's the way I found out by searching in the tree in lpc24xx
> and lpc176x bsps. Pity I've not found altera-cyclone-v at that time
> since this looks even more similar to what I need to achieve here. Will
> need to analyze it better (weekend task).
> 
> As I'm still trying to understand better memory allocation in RTEMS, I'm
> of course open to any idea how to implement this in the most clean way
> acceptable for RTEMS and not using _Heap_Extend() -- if it would not be
> allowed or right thing to do or scheduled for future removal.

In RTEMS 6, the BSP has to provide a _Memory_Get() function which 
returns the memory areas which may be used by RTEMS at runtime. Most 
BSPs just return a single memory area. A BSP can also return multiple 
memory areas:

static Memory_Area _Memory_Areas[ 123 ];

static const Memory_Information _Memory_Information =
   MEMORY_INFORMATION_INITIALIZER( _Memory_Areas );

static void bsp_memory_initialize( void )
{
   size_t i;

   for ( i = 0; i < RTEMS_ARRAY_SIZE( _Memory_Areas ); ++i ) {
     _Memory_Initialize( &_Memory_Areas[ i ], begin( i ), end( i ) );
   }
}

RTEMS_SYSINIT_ITEM(
   bsp_memory_initialize,
   RTEMS_SYSINIT_MEMORY,
   RTEMS_SYSINIT_ORDER_MIDDLE
);

const Memory_Information *_Memory_Get( void )
{
   return &_Memory_Information;
}

What the patch set changed is that the BSP provides specialized 
implementations to initialize the RTEMS Workspace and the separate C 
Program Heap according to the _Memory_Get() implementation.

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