Class MultilevelBitmapFrameAllocator

kernel/src/memory/frame_allocator.rs:78–95

An allocator which uses bitmaps to keep track of available frames At the lowest level one bit represents one frame (1 = available) Higher levels indicate whether chunks of 32 bits at level-1 have ANY non-zero bits. Multiple levels are used, until the top level has only a single chunk of up to 32 bits.

/// only a single chunk of up to 32 bits.
///
pub struct MultilevelBitmapFrameAllocator {
    /// Virtual address of the first level 2 entry
    /// Each entry is 32 bits long, one bit per level-1 entry
    bitmap_virt_addr: [VirtAddr; FRAME_ALLOCATOR_MAX_LEVELS],

    /// Number of frames
    nframes: u64,

    /// Number of levels
    nlevels: usize,

    /// Physical start address of the frames
    frame_phys_addr: PhysAddr,

    /// Stack of up to FRAME_ALLOCATOR_STACK_SIZE frames
    frame_stack: [u64; FRAME_ALLOCATOR_STACK_SIZE],
    frame_stack_number: usize,
}

impl MultilevelBitmapFrameAllocator {