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® 9-2 Typical Memory Layout sysPhysMemTop() sysMemTop() FREE_RAM_ADRS RAM_LOW_ADRS LOCAL_MEM_LOCAL_ADRS.

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Presentation on theme: "® 9-2 Typical Memory Layout sysPhysMemTop() sysMemTop() FREE_RAM_ADRS RAM_LOW_ADRS LOCAL_MEM_LOCAL_ADRS."— Presentation transcript:

1 ® 9-2 Typical Memory Layout sysPhysMemTop() sysMemTop() FREE_RAM_ADRS RAM_LOW_ADRS LOCAL_MEM_LOCAL_ADRS

2 ® 9-3 Target Server Memory Pool A pool of memory on the target reserved for use by the Tornado tools: –Dynamic loading of object modules. –Passing string arguments to tasks spawned on target. –Creation of variables from WindSh. The target server manages the pool, keeping overhead such as block lists on the host. The initial size of the target server memory pool is configured by WDB_POOL_SIZE. The default is 1/16 of sysMemTop( ) - FREE_RAM_ADRS. Additional memory is silently allocated from the system memory pool if needed.

3 ® 9-4 System Memory Pool Used for dynamic memory allocation in programs: –malloc( ). –Creating tasks (stack and TCB). –VxWorks memory requests. Initialized at system start-up. –Can modify USER_RESERVED_MEM to reserve memory for application-specific use. –May need to modify sysPhysMemTop( ) (or just LOCAL_MEM_SIZE) when adding memory to your board. Check your BSP documentation. To add off-board memory: void memAddToPool (pPool, poolSize) pPool must be the local address of the memory.

4 ® 9-5 Allocating/Releasing Memory To dynamically allocate memory: void *malloc (nBytes) Returns a pointer to the newly allocated memory or NULL on error. Uses first-fit algorithm. –Free memory is stored in a linked list. –Some (small) overhead for each malloc( ). To release allocated memory: void free (ptr) Adjacent blocks are coalesced.

5 ® 9-6 Debugging Options Default malloc( ) debugging: If request too large, log an error message. Default free( ) debugging: –Check block for consistency. –If corrupted: suspend task, log error message. Can change default debugging options with: void memOptionsSet (options) Options can be: + MEM_ALLOC_ERROR_LOG_FLAG - MEM_ALLOC_ERROR_SUSPEND_FLAG + MEM_BLOCK_CHECK + MEM_BLOCK_ERROR_LOG_FLAG + MEM_BLOCK_ERROR_SUSPEND_FLAG

6 ® 9-7 Examining Memory Use the Browser. Enter the memory partition ID in the Show box. System Memory Pool Size Currently Allocated Free Blocks Total Allocated Free List

7 ® 9-8 Additional System Memory Management Routines void * calloc (nElems, size)Allocate zeroed memory for an array. void * realloc (ptr, newSize)Resize an allocated block. The block may be moved. int memFindMax( )Returns the size of the largest free block in system memory.

8 ® 9-9 Fine Tuning For fast, deterministic allocation of fixed size buffers, use message queues instead of malloc( ).

9 ® 9-10 Generic Partition Manager VxWorks provides low-level routines to create and manipulate alternate memory pools. High-level routines like malloc( ) and free( ) call these lower level routines, specifying the system memory pool. Application may use alternate memory partitions to reduce fragmentation. Application may use alternate memory partitions to manage memory with different properties.

10 ® 9-11 Creating a Memory Partition PART_ID memPartCreate (pPool, size) pPoolPointer to memory for this partition. sizeSize of memory partition in bytes. Returns a partition id (PART_ID), or NULL on error. The memory for this partition (pPool) may be taken from: –A separate memory board. –A block allocated from the system memory partition. –The top of the CPU board’s RAM.

11 ® 9-12 Managing Memory Partitions System partition management routines call routines listed below, specifying the PART_ID as memSysPartId. GenericSystem Memory Pool memPartAlloc( )malloc( ) memPartFree( )free( ) memPartShow( )memShow( ) memPartAddToPool( )memAddToPool( ) memPartOptionsSet( )memOptionsSet( ) memPartRealloc( )realloc( ) memPartFindMax( )memFindMax( )

12 ® 9-13 Example Creating a Memory Partition partId =memPartCreate(pMemory,100000) ->partId =memPartCreate(pMemory,100000) new symbol “partId” added to symbol table. partId = 0x23ff318: value = = 0x23ff328 = partId + 0x10 ->ptr=memPartAlloc(partId,200) new symbol “ptr” added to symbol table. ptr = 0x23ff2ec: value = = 0x23e8898 show partId ->show partId status bytes blocks ave block max block current free alloc cumulative alloc

13 ® 9-14 Summary Standard C routines are used for dynamic memory allocation. To configure the system memory pool: –Modify sysPhysMemTop( ). –Specify USER_RESERVED_MEM. –Call memAddToPool( ). For fast, deterministic allocation of fixed size buffers, use message queues instead of malloc( ). Create separate memory partition for off-board memory, or to help reduce fragmentation.


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