Re: bootmem allocator

[William Lee Irwin III <wli@holomorphy.com>]

On Sat, Feb 02, 2002 at 10:50:00AM -0800, Mcen navaraj wrote:
> please explain me what is the use of the bootmem
> allocator ?
> i am reading the bootmem.c file but i cannot get the
> full details about the bootmem allocator.
> tell me what is the use of the node_boot_start
> variable in the bootmem_data structure in the mmzone.h
> ? please explain the use of each variable in the
> bootmem_data structure .
> please explain this as simple as possible.
> i am newbie to linux kernel.
> bye

It's undocumented.

typedef struct bootmem_data {
	/*
	 * The lowest address of available memory within the node.
	 */
        unsigned long node_boot_start;

	/*
	 * The highest page frame number of available memory
	 * within the node.
	 */
        unsigned long node_low_pfn;

	/*
	 * Pointer to the beginning of the bitmap, which is
	 * linearly-scanned using atomic bit operations.
	 */
        void *node_bootmem_map;

	/*
	 * In order to deal with sequential sub-page-sized allocations,
	 * these state variables keeps track of the precise address of
	 * the last allocation. Then some really dense code is used to
	 * figure out where the next block to be allocated comes from.
	 */
        unsigned long last_offset;	/* offset into the page */
        unsigned long last_pos;		/* position in the bitmap */
} bootmem_data_t;


Cheers,
Bill
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