// Overview / API / FAQ / Resources

mem: Memory Allocator library

https://en.wikipedia.org/wiki/Allocator_C++

Features

• Single header (https://raw.githubusercontent.com/qlibs/mem/main/mem) / C++20 module (https://raw.githubusercontent.com/qlibs/mem/main/mem.cppm)
• C++23 standard compliant API
• Verifies itself upon include/import (can be disabled with -DNTEST - see FAQ)

Requirements

• C++20+ (clang++12+, g++11+) / Linux* / numactl*

Overview

import mem;

int main() {
  static_assert(mem::allocator_like<std::allocator<int>>);
  static_assert(mem::allocator_like<mem::allocator::aligned<int, std::align_val_t(64u)>>);
  static_assert(mem::allocator_like<mem::allocator::stack<int, 1024u>>);
  static_assert(mem::allocator_like<mem::allocator::transparent_huge_pages<int>>);
  static_assert(mem::allocator_like<mem::allocator::huge_pages<int>>);
  static_assert(mem::allocator_like<mem::allocator::numa<int>>);

  {
    std::vector<int, mem::allocator::aligned<int, std::align_val_t(64u)>> v{};
    std::vector<int, mem::allocator::stack<int, 1024u>> v{};
    // echo 20 > /proc/sys/vm/nr_hugepages
    std::vector<int, mem::allocator::huge_pages<int>> v{};
    // echo always > /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled
    std::vector<int, mem::allocator::transparent_huge_pages<int>> v{};
    // -lnuma # requires libnuma-dev
    std::vector<int, mem::allocator::numa<int>> v{};
  }
}

API

• https://github.com/qlibs/mem/blob/main/mem.cppm

FAQ

• How to disable running tests at compile-time?
  When -DNTEST is defined static_asserts tests wont be executed upon inclusion. Note: Use with caution as disabling tests means that there are no gurantees upon inclusion that given compiler/env combination works as expected.

• Similar projects?
  std::pmr

Resources

std::allocator

• https://eel.is/c++draft/allocator.requirements
• https://en.cppreference.com/w/cpp/memory/allocator

Transparent Huge Pages

• https://www.kernel.org/doc/html/latest/admin-guide/mm/transhuge.html
• https://man7.org/linux/man-pages/man2/madvise.2.html
• https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/6/html/performance_tuning_guide/s-memory-transhuge

Huge Pages

• https://www.kernel.org/doc/html/latest/admin-guide/mm/hugetlbpage.html
• https://www.man7.org/linux/man-pages/man2/mmap.2.html
• https://www.intel.com/content/www/us/en/docs/programmable/683840/1-2-1/enabling-hugepages.html
• https://github.com/libhugetlbfs/libhugetlbfs
• https://wiki.debian.org/Hugepages

Non Uniform Memory Access

• https://en.wikipedia.org/wiki/Non-uniform_memory_access
• https://man7.org/linux/man-pages/man3/numa.3.html
• https://www.intel.com/content/www/us/en/developer/articles/technical/use-intel-quickassist-technology-efficiently-with-numa-awareness.html

License

• MIT