Function: malloc

Applicable Products

Description

Allocates linear memory of the size on the device and returns the pointer to the allocated memory through dev_ptr. The start address of the memory is 64-byte aligned. The memory allocated by this API needs to be freed by calling acl.rt.free.

The allocated memory is byte-aligned. The alignment policy varies depending on the product model.

• For the Ascend 950PR / Ascend 950DT , the memory allocated by this API is byte-aligned. The size bytes requested by users are rounded up to the nearest multiple of 32 bytes.
• For the product models below, the memory allocated by this API is byte-aligned. The size bytes requested by users are rounded up to the nearest multiple of 32 bytes, with an additional 32 bytes added. However, for huge pages with the memory allocation granularity of 1 GB, to save huge pages, this API only rounds up the size requested by users to an integer multiple of 32 bytes, but does not add an extra 32 bytes.
  • Atlas A3 training products / Atlas A3 inference products
  • Atlas A2 training products / Atlas A2 inference products
  • Atlas 200I/500 A2 inference products
  • Atlas inference products
  • Atlas training products

Prototype

• C Prototype

  1	aclError aclrtMalloc(void **devPtr, size_t size, aclrtMemMallocPolicy policy)

• Python Function

  1	dev_ptr, ret = acl.rt.malloc(size, policy)

Parameters

Return Values

Restrictions

• Media data processing has higher requirements on the memory for storing the input and output data (for example, the start address of the memory must be 128-byte aligned). Therefore, the following dedicated memory allocation APIs are required:
  • When the media data processing V1 API is called to perform operations such as cropping and resizing on images, the acl.media.dvpp_malloc API is called to allocate memory.
  • When the media data processing V2 API is called to perform operations such as cropping and resizing on images, the acl.himpi.dvpp_malloc API is called to allocate memory.
• The memory allocated by this API is not initialized. Call acl.rt.memset to initialize the memory and clear random numbers in the memory before using the memory.
• This API does not perform implicit device synchronization or stream synchronization. The memory allocation result, either success or failure, is returned immediately.
• The value of policy can only be a single enumeration item and cannot be multiple enumeration items combined with bitwise OR.
• For the ACL_MEM_MALLOC_HUGE_FIRST_P2P and ACL_MEM_MALLOC_HUGE_ONLY_P2P policies, you are advised to use the acl.rt.malloc_with_cfg API. Otherwise, performance issues may occur or memory may fail to be allocated.
• Memory allocated by the acl.rt.malloc call needs to be freed by the acl.rt.free call.
• Performance deterioration will be caused by the frequent calling of acl.rt.malloc to allocate memory and acl.rt.free to free memory. You are advised to allocate or manage memory in advance to avoid frequent memory allocation and deallocation.
• The allocation size of acl.rt.malloc is the input size rounded up to the nearest multiple of 32 bytes, plus 32 bytes.
  If you use this API to allocate a large memory block, and divide and manage the memory, each memory segment must meet the following requirements:

  • The memory size is rounded up to the nearest multiple of 32 plus 32 bytes (m = ALIGN_UP[len,32] + 32 bytes).
  • The memory start address must be 64-byte aligned (ALIGN_UP[m,64]).

  

  len indicates the size of a memory segment. ALIGN_UP[len,k] indicates rounding up to a multiple of k bytes as in this formula: ((len – 1)/k + 1) x k.