vecmem::details::binary_page_memory_resource_impl Struct Reference

Implementation of vecmem::binary_page_memory_resource. More...

#include </home/runner/work/vecmem/vecmem/core/src/memory/details/binary_page_memory_resource_impl.hpp>

Classes
struct	page_ref
	Helper class to refer to pages in superpages. More...
struct	superpage
	Container for superpages in our buddy allocator. More...

Public Types
enum class	page_state { OCCUPIED , VACANT , SPLIT , NON_EXTANT }
	The different possible states a page can be in. More...

Public Member Functions
	binary_page_memory_resource_impl (memory_resource &upstream)
	Constructor, on top of another memory resource.
std::optional< page_ref >	find_free_page (std::size_t)
	Find the smallest free page that could fit the requested size.
void	allocate_upstream (std::size_t)
	Perform an upstream allocation.
Functions implementing the @c vecmem::memory_resource interface
void *	allocate (std::size_t size, std::size_t align)
	Allocate a blob of memory.
void	deallocate (void *p, std::size_t size, std::size_t align)
	De-allocate a previously allocated memory blob.

Public Attributes
memory_resource &	m_upstream
std::vector< superpage >	m_superpages

Static Public Attributes
static constexpr std::size_t	min_superpage_size = 20
	The minimum size (log_2) of superpages in our buddy allocator.
static constexpr std::size_t	delta_superpage_size = 8
	The maximum difference (log_2) between the size of the superpage and its smallest page.
static constexpr std::size_t	min_page_size = 8
	The minimum size (log_2) of pages in our buddy allocator.

Detailed Description

Implementation of vecmem::binary_page_memory_resource.

Member Enumeration Documentation

page_state

enum class vecmem::details::binary_page_memory_resource_impl::page_state

strong

The different possible states a page can be in.

We define three different page states. An OCCUPIED state is non-free, and used directly (thus it is not split). A VACANT page is not split and unused. A SPLIT page is split in two, and has two children pages. Non-extant pages do not exist, because their parent is not split.

Member Function Documentation

allocate_upstream()

void vecmem::details::binary_page_memory_resource_impl::allocate_upstream

(

std::size_t

size

)

Perform an upstream allocation.

This method performs an allocation through the upstream memory resource and immediately creates a page to represent this new chunk of memory.

find_free_page()

std::optional< binary_page_memory_resource_impl::page_ref > vecmem::details::binary_page_memory_resource_impl::find_free_page

(

std::size_t

size

)

Find the smallest free page that could fit the requested size.

Note that this method might return split pages if both children are free. In that case, the page should first be unsplit. In some cases, the returned page might be (significantly) larger than the request, and should be split before allocating.

Member Data Documentation

delta_superpage_size

constexpr std::size_t vecmem::details::binary_page_memory_resource_impl::delta_superpage_size = 8

staticconstexpr

The maximum difference (log_2) between the size of the superpage and its smallest page.

The default value of 8 indicates that there are at most 8 orders of magnitude (log_2) between the size of the superpage, and the smallest page in it.

min_page_size

constexpr std::size_t vecmem::details::binary_page_memory_resource_impl::min_page_size = 8

staticconstexpr

The minimum size (log_2) of pages in our buddy allocator.

The default value of 2 indicates that the size is equal to 2^8=256 bytes.

min_superpage_size

constexpr std::size_t vecmem::details::binary_page_memory_resource_impl::min_superpage_size = 20

staticconstexpr

The minimum size (log_2) of superpages in our buddy allocator.

The default value of 20 indicates the the default size is equal to 2^20=1048576 bytes.

Note

Pages can (counterintuitively) be smaller than this value. This happens if an allocation is so small that the allocation size plus the delta is smaller than the minimum page size. The minimum superpage size indicates the size of the superpage above which we will not optimistically overallocate.

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The documentation for this struct was generated from the following files:

• core/src/memory/details/binary_page_memory_resource_impl.hpp
• core/src/memory/details/binary_page_memory_resource_impl.cpp