FreeRTOS

Memory Allocation

• heap

  1. Heap Init ,如果沒有使用過的話

  2. xWantSize +=HeapStructSize 和做 alingment

     • heapSTRUCT_SIZE = ( ( sizeof( BlockLink_t ) + ( portBYTE_ALIGNMENT - 1 ) ) & ~portBYTE_ALIGNMENT_MASK );

  3. 如果( xWantedSize > 0 ) && (xWantedSize <=xFreeBytesRemaining ) ，繼續 allocate

  4. 找到第一個 足夠的 BlockSize 進行使用

  5. 如果要使用的 BlockSize > heapMINIMUM_BLOCK_SIZE，則把它進行分割加入 Free List

     ​​​​​​​​    pxNewBlockLink = (void *) ( ( (uint8_t *) pxBlock ) + xWantedSize ); 
     ​​​​​​​​    pxNewBlockLink->xBlockSize = pxBlock->xBlockSize - xWantedSize; 
     ​​​​​​​​    pxBlock->xBlockSize = xWantedSize; 
     ​​​​​​​​    prvInsertBlockIntoFreeList( ( pxNewBlockLink ) );
     

     • heapMINIMUM_BLOCK_SIZE = heapSTRUCT_SIZE *2
     • prvInsertBlockIntoFreeList( ( pxNewBlockLink ) );
       • Heap2 : 按照 Block Size 大小排序加入 Free List (小 =>大)
       • Heap 4 : 按照 Block Address 高低排序加入 Free List (小 =>大)，會在這個時候做 continuous block 的合併

  6. retuen allocate address

hart:

A component that contains a hardware execution context, which
includes all the state mandated by the RISC-V ISA: a PC and some registers.

core:

A component that contains one or more harts that share a
single independent instruction fetch unit.