MEMKINDALLOCATOR(3)

NAME
libmemkind::static_kind::allocator<T> - The C++ allocator compatible with the C++ standard library allocator concepts
Note: memkind_allocator.h functionality is considered as stable API (STANDARD API).

SYNOPSIS
#include <memkind_allocator.h>

Link with -lmemkind

libmemkind::static_kind::allocator(libmemkind::kinds kind);
template <typename U> libmemkind::static_kind::allocator<T>::allocator(const libmemkind::static_kind::allocator<U>&) noexcept;
template <typename U> libmemkind::static_kind::allocator(const allocator<U>&& other) noexcept;
libmemkind::static_kind::allocator<T>::~allocator();
T *libmemkind::static_kind::allocator<T>::allocate(std::size_t n) const;
void libmemkind::static_kind::allocator<T>::deallocate(T *p, std::size_t n) const;
template <class U, class... Args> void libmemkind::static_kind::allocator<T>::construct(U *p, Args... args) const;
void libmemkind::static_kind::allocator<T>::destroy(T *p) const;

DESCRIPTION
The libmemkind::static_kind::allocator<T> is intended to be used with STL containers to allocate from static kinds memory. Memory management is based on memkind library. Refer memkind(3) man page for more details.

The libmemkind::kinds specifies allocator static kinds of memory, representing type of memory which offers different characteristics. The available types of allocator kinds of memory:

libmemkind::kinds::DEFAULT Default allocation using standard memory and default page size.

libmemkind::kinds::HIGHEST_CAPACITY Allocate from a NUMA node(s) that has the highest capacity among all nodes in the system.

libmemkind::kinds::HIGHEST_CAPACITY_PREFERRED Same as libmemkind::kinds::HIGHEST_CAPACITY except that if there is not enough memory in the NUMA node that has the highest capacity in the local domain to satisfy the request, the allocation will fall back on other memory NUMA nodes. Note: For this kind, the allocation will not succeed if there are two or more NUMA nodes that have the highest capacity.

libmemkind::kinds::HIGHEST_CAPACITY_LOCAL Allocate from a NUMA node that has the highest capacity among all NUMA Nodes from the local domain. NUMA Nodes have the same local domain for a set of CPUs associated with them, e.g. socket or sub-NUMA cluster. Note: If there are multiple NUMA nodes in the same local domain that have the highest capacity - allocation will be done from NUMA node with worse latency attribute. This kind requires locality information described in SYSTEM CONFIGURATION section.

libmemkind::kinds::HIGHEST_CAPACITY_LOCAL_PREFERRED Same as libmemkind::kinds::HIGHEST_CAPACITY_LOCAL except that if there is not enough memory in the NUMA node that has the highest capacity to satisfy the request, the allocation will fall back on other memory NUMA nodes.

libmemkind::kinds::LOWEST_LATENCY_LOCAL Allocate from a NUMA node that has the lowest latency among all NUMA Nodes from the local domain. NUMA Nodes have the same local domain for a set of CPUs associated with them, e.g. socket or sub-NUMA cluster. Note: If there are multiple NUMA nodes in the same local domain that have the lowest latency - allocation will be done from NUMA node with smaller memory capacity. This kind requires locality and memory performance characteristics information described in SYSTEM CONFIGURATION section.

libmemkind::kinds::LOWEST_LATENCY_LOCAL_PREFERRED Same as libmemkind::kinds::LOWEST_LATENCY_LOCAL except that if there is not enough memory in the NUMA node that has the lowest latency to satisfy the request, the allocation will fall back on other memory NUMA nodes.

libmemkind::kinds::HIGHEST_BANDWIDTH_LOCAL Allocate from a NUMA node that has the highest bandwidth among all NUMA Nodes from the local domain. NUMA Nodes have the same local domain for a set of CPUs associated with them, e.g. socket or sub-NUMA cluster. Note: If there are multiple NUMA nodes in the same local domain that have the highest bandwidth - allocation will be done from NUMA node with smaller memory capacity. This kind requires locality and memory performance characteristics information described in SYSTEM CONFIGURATION section.

libmemkind::kinds::HIGHEST_BANDWIDTH_LOCAL_PREFERRED Same as libmemkind::kinds::HIGHEST_BANDWIDTH_LOCAL except that if there is not enough memory in the NUMA node that has the highest bandwidth to satisfy the request, the allocation will fall back on other memory NUMA nodes.

libmemkind::kinds::HUGETLB Allocate from standard memory using huge pages. Note: This kind requires huge pages configuration described in SYSTEM CONFIGURATION section.

libmemkind::kinds::INTERLEAVE Allocate pages interleaved across all NUMA nodes with transparent huge pages disabled.

libmemkind::kinds::HBW Allocate from the closest high bandwidth memory NUMA node at the time of allocation. If there is not enough high bandwidth memory to satisfy the request, errno is set to ENOMEM and the allocated pointer is set to NULL. Note: This kind requires memory performance characteristics information described in SYSTEM CONFIGURATION section.

libmemkind::kinds::HBW_ALL Same as libmemkind::kinds::HBW except decision regarding closest NUMA node is postponed until the time of first write.

libmemkind::kinds::HBW_HUGETLB Same as libmemkind::kinds::HBW except the allocation is backed by huge pages. Note: This kind requires huge pages configuration described in SYSTEM CONFIGURATION section.

libmemkind::kinds::HBW_ALL_HUGETLB Combination of libmemkind::kinds::HBW_ALL and libmemkind::kinds::HBW_HUGETLB properties. Note: This kind requires huge pages configuration described in SYSTEM CONFIGURATION section.

libmemkind::kinds::HBW_PREFERRED Same as libmemkind::kinds::HBW except that if there is not enough high bandwidth memory to satisfy the request, the allocation will fall back on standard memory.

libmemkind::kinds::HBW_PREFERRED_HUGETLB Same as libmemkind::kinds::HBW_PREFERRED except the allocation is backed by huge pages. Note: This kind requires huge pages configuration described in SYSTEM CONFIGURATION section.

libmemkind::kinds::HBW_INTERLEAVE Same as libmemkind::kinds::HBW except that the pages that support the allocation are interleaved across all high bandwidth nodes and transparent huge pages are disabled.

libmemkind::kinds::REGULAR Allocate from regular memory using the default page size. Regular means general purpose memory from the NUMA nodes containing CPUs.

libmemkind::kinds::DAX_KMEM Allocate from the closest persistent memory NUMA node at the time of allocation. If there is not enough memory in the closest persistent memory NUMA node to satisfy the request, errno is set to ENOMEM and the allocated pointer is set to NULL.

libmemkind::kinds::DAX_KMEM_ALL Allocate from the closest persistent memory NUMA node available at the time of allocation. If there is not enough memory on any of persistent memory NUMA nodes to satisfy the request, errno is set to ENOMEM and the allocated pointer is set to NULL.

libmemkind::kinds::DAX_KMEM_PREFERRED Same as libmemkind::kinds::DAX_KMEM except that if there is not enough memory in the closest persistent memory NUMA node to satisfy the request, the allocation will fall back on other memory NUMA nodes. Note: For this kind, the allocation will not succeed if two or more persistent memory NUMA nodes are in the same shortest distance to the same CPU on which process is eligible to run. Check on that eligibility is done upon starting the application.

libmemkind::kinds::DAX_KMEM_INTERLEAVE Same as libmemkind::kinds::DAX_KMEM except that the pages that support the allocation are interleaved across all persistent memory NUMA nodes.

All public member types and functions correspond to standard library allocator concepts and definitions. The current implementation supports C++11 standard.

Template arguments:
T is an object type aliased by value_type.
U is an object type.

Note:
T *libmemkind::static_kind::allocator<T>::allocate(std::size_t n) allocates memory using memkind_malloc(). Throw std::bad_alloc when:
    n = 0
    or there is not enough memory to satisfy the request.

libmemkind::static_kind::allocator<T>::deallocate(T *p, std::size_t n) deallocates memory associated with pointer returned by allocate() using memkind_free().

SYSTEM CONFIGURATION
Interfaces for obtaining 2MB (HUGETLB) memory need allocated huge pages in the kernel's huge page pool.

HUGETLB (huge pages)
    Current number of "persistent" huge pages can be read from /proc/sys/vm/nr_hugepages file. Proposed way of setting hugepages is: sudo sysctl vm.nr_hugepages=<number_of_hugepages>. More information can be found here: https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt

Interfaces for obtaining locality information are provided by libhwloc dependency. Functionality based on locality requires that memkind library is configured and built with the support of libhwloc (./configure --enable-hwloc).

Interfaces for obtaining memory performance characteristics information are based on HMAT (Heterogeneous Memory Attribute Table) https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf Functionality based on memory performance characteristics requires that platform configuration fully supports HMAT and memkind library is configured and built with the support of libhwloc (./configure --enable-hwloc).

Note: For a given target NUMA Node, the OS exposes only the performance characteristics of the best performing NUMA node.

libhwloc can be reached on: https://www.open-mpi.org/projects/hwloc

COPYRIGHT
Copyright (C) 2019 - 2021 Intel Corporation. All rights reserved.

SEE ALSO
memkind(3)