Crate page_allocator

Provides an allocator for virtual memory pages. The minimum unit of allocation is a single page.

This also supports early allocation of pages (up to 32 separate chunks) before heap allocation is available, and does so behind the scenes using the same single interface.

Once heap allocation is available, it uses a dynamically-allocated list of page chunks to track allocations.

The core allocation function is allocate_pages_deferred(), but there are several convenience functions that offer simpler interfaces for general usage.

Notes

This allocator only makes one attempt to merge deallocated pages into existing free chunks for de-fragmentation. It does not iteratively merge adjacent chunks in order to maximally combine separate chunks into the biggest single chunk. Instead, free chunks are lazily merged only when running out of address space or when needed to fulfill a specific request.

Structs

• AllocatedPages
  Represents a range of allocated VirtualAddresses, specified in Pages.
• DeferredAllocAction
  A series of pending actions related to page allocator bookkeeping, which may result in heap allocation.

Enums

• AllocationError
  Possible errors returned by the page allocator.
• AllocationRequest
  Possible options when requesting pages from the page allocator.

Functions

• allocate_pages
  Allocates the given number of pages with no constraints on the starting virtual address.
• allocate_pages_at
  Allocates the given number of pages starting at (inclusive of) the page containing the given VirtualAddress.
• allocate_pages_by_bytes
  Allocates pages with no constraints on the starting virtual address, with a size given by the number of bytes.
• allocate_pages_by_bytes_at
  Allocates pages starting at the given VirtualAddress with a size given in number of bytes.
• allocate_pages_by_bytes_deferred
  Similar to allocated_pages_deferred(), but accepts a size value for the allocated pages in number of bytes instead of number of pages.
• allocate_pages_by_bytes_in_range
  Allocates pages with a size given in number of bytes with the constraint that they must be within the given inclusive range of pages.
• allocate_pages_deferred
  The core page allocation routine that allocates the given number of virtual pages, optionally at the requested starting VirtualAddress.
• allocate_pages_in_range
  Allocates the given number of pages with the constraint that they must be within the given inclusive range of pages.
• init
  Initialize the page allocator.