.. meta:: :description: rocSHMEM intra-kernel networking runtime for AMD dGPUs on the ROCm platform. :keywords: rocSHMEM, API, ROCm, documentation, HIP, Networking, Communication .. _rocshmem-api-memory-management: --------------------------- Memory management routines --------------------------- ROCSHMEM_MALLOC --------------- .. cpp:function:: __host__ void *rocshmem_malloc(size_t size) :param size: Memory allocation size in bytes. :returns: A pointer to the allocated memory on the symmetric heap. If a valid allocation cannot be made, it returns ``NULL``. **Description:** This routine allocates memory of ``size`` bytes from the symmetric heap. This is a collective operation and must be called by all PEs. ROCSHMEM_ALIGN -------------- .. cpp:function:: __host__ void *rocshmem_align(size_t alignment, size_t size) :param alignment: Required pointer alignment in bytes. Must be a power of two **and** a multiple of ``sizeof(void *)``. :param size: Memory allocation size in bytes. :returns: A pointer to the allocated memory on the symmetric heap, aligned to ``alignment`` bytes. Returns ``NULL`` if ``alignment`` is invalid (not a power of two, or not a multiple of ``sizeof(void *)``) or if the allocation cannot be satisfied. **Description:** This routine allocates ``size`` bytes from the symmetric heap and returns a pointer that is aligned to ``alignment`` bytes. It is a collective operation and must be called by all PEs with identical ``alignment`` and ``size`` arguments. Constraints on ``alignment`` (mirroring OpenSHMEM ``shmem_align`` and POSIX ``posix_memalign`` semantics): * ``alignment`` must be a power of two. * ``alignment`` must be a multiple of ``sizeof(void *)``. Any power of two that is at least ``sizeof(void *)`` (8 bytes on a 64-bit build) automatically satisfies both rules. The smallest accepted value is therefore ``sizeof(void *)``; accepted values are ``sizeof(void *), 2*sizeof(void *), 4*sizeof(void *), ...``. Invalid values (``0``, ``1``, ``2``, ``4`` on 64-bit, or any non power-of-two) cause the routine to return ``NULL`` and emit a warning. The collective barrier is still entered so other PEs do not deadlock. Notes: * ``alignment`` values less than or equal to the default symmetric-heap alignment (128 bytes) yield a 128-byte aligned pointer, identical to :ref:`rocshmem_malloc`. ROCSHMEM_CALLOC --------------- .. cpp:function:: __host__ void *rocshmem_calloc(size_t count, size_t size) :param count: Number of elements. :param size: Size of each element in bytes. :returns: A pointer to ``count * size`` bytes of zero-initialized memory on the symmetric heap, or ``NULL`` if ``count`` or ``size`` is ``0``, if ``count * size`` overflows ``size_t``, or if the allocation cannot be satisfied. **Description:** This routine allocates memory for an array of ``count`` elements of ``size`` bytes each from the symmetric heap and zero-initializes the allocation. It is a collective operation and must be called by all PEs with identical ``count`` and ``size`` arguments. The returned pointer satisfies the same default symmetric-heap alignment as :ref:`rocshmem_malloc`. Mirrors OpenSHMEM ``shmem_calloc`` semantics. Notes: * If ``count`` is ``0``, ``size`` is ``0``, or ``count * size`` would overflow ``size_t``, this routine returns ``NULL`` (and emits a warning for the overflow case). The collective barrier is still entered on every return path so other PEs do not deadlock. ROCSHMEM_FREE ------------- .. cpp:function:: __host__ void rocshmem_free(void *ptr) :param ptr: A pointer to previously allocated memory on the symmetric heap. :returns: None. **Description:** This routine frees a memory allocation from the symmetric heap. It is a collective operation and must be called by all PEs. ROCSHMEM_BUFFER_REGISTER ------------------------ .. cpp:function:: __host__ int rocshmem_buffer_register(void *addr, size_t length); :param addr: Pointer to previously allocated memory :param length: Length of addr :returns: ROCSHMEM_SUCCESS or an error. **Description:** Registers a user-allocated buffer. This buffer can be used as a local buffer to most rocSHMEM communication calls. It is erroneous to use it for a remote buffer. ROCSHMEM_BUFFER_UNREGISTER -------------------------- .. cpp:function:: __host__ int rocshmem_buffer_unregister(void *addr); :param addr: Pointer to previously registered memory :returns: ROCSHMEM_SUCCESS or an error. **Description:** Deregisters a previously registered buffer that was registered using `rocshmem_buffer_register`. ROCSHMEM_BUFFER_UNREGISTER_ALL ------------------------------ .. cpp:function:: __host__ void rocshmem_buffer_unregister_all(); **Description:** Deregisters all buffers that were previously registered using `rocshmem_buffer_register`. ROCSHMEM_BUFFER_REGISTER_SYMMETRIC ---------------------------------- .. cpp:function:: __host__ void *rocshmem_buffer_register_symmetric(void *addr, size_t length); :param addr: Pointer to previously allocated VMM memory. :param length: Length of ``addr`` in bytes. :returns: The rocSHMEM-managed symmetric address on success, ``NULL`` otherwise. **Description:** Registers a user-allocated buffer so that it can be used as the remote target of RMA operations. Unlike :ref:`rocshmem_buffer_register`, this is a **collective** operation that must be called by all PEs with a buffer of the same ``length``. The call maps the user's buffer to a rocSHMEM-managed virtual address and returns it. That returned address (**not** ``addr``) is the symmetric handle the caller must use as the target for RMA routines, and the same address must later be passed to :ref:`rocshmem_buffer_unregister_symmetric`. Notes: * This routine is restricted to memory allocated through the HIP Virtual Memory Management (VMM) APIs (ROCm 7.2 or newer). Passing a non-VMM pointer returns ``NULL``. * Each PE may supply a different underlying buffer, but all PEs must agree on ``length`` and on the buffer's alignment so the region is symmetric across the job. * The underlying buffer ranges must not overlap a region that is already registered. * The maximum number of concurrently registered symmetric buffers is bounded by the ``ROCSHMEM_MAX_SYMM_REGIONS`` environment variable. Backend behavior: * **IPC backend:** peer buffers are mapped into the local address space, so registered buffers are reached directly through inter-process copies. * **GDA backend:** registered buffers are registered with each NIC's protection domain and are reachable over the NIC by every peer. When the IPC fast path is additionally available for node-local peers (see ``ROCSHMEM_DISABLE_MIXED_IPC``), the buffer is also exposed to those peers over IPC, and their accesses use the IPC path in preference to the NIC; the NIC registration remains in place and is used for all other peers. * **RO (reverse offload) backend:** symmetric user-buffer registration is not supported; this routine returns ``NULL``. ROCSHMEM_BUFFER_UNREGISTER_SYMMETRIC ------------------------------------ .. cpp:function:: __host__ int rocshmem_buffer_unregister_symmetric(void *addr); :param addr: The symmetric address returned by ``rocshmem_buffer_register_symmetric``. :returns: ROCSHMEM_SUCCESS on success, ROCSHMEM_ERROR otherwise. **Description:** Deregisters a buffer that was previously registered using :ref:`rocshmem_buffer_register_symmetric`. This is a **collective** operation that must be called by all PEs that participated in the matching ``rocshmem_buffer_register_symmetric`` call. The ``addr`` argument must be the rocSHMEM-managed symmetric address returned by ``rocshmem_buffer_register_symmetric`` (not the caller's original buffer pointer). The call unmaps the rocSHMEM-managed virtual address; the user's original buffer is left untouched.