xref: /dflybsd-src/sys/kern/subr_alist.c (revision 33ec1deb6a5f5b42630d5d97405947a1029be8de)

/*
 * ALIST.C -	Bitmap allocator/deallocator, using a radix tree with hinting.
 *		Unlimited-size allocations, power-of-2 only, power-of-2
 *		aligned results only.
 *
 * Copyright (c) 2007 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 * This module has been adapted from the BLIST module, which was written
 * by Matthew Dillon many years ago.
 *
 * This module implements a general power-of-2 bitmap allocator/deallocator.
 * All allocations must be in powers of 2 and will return similarly aligned
 * results.  The module does not try to interpret the meaning of a 'block'
 * other then to return ALIST_BLOCK_NONE on an allocation failure.
 *
 * A maximum of 2 billion blocks is supported so, for example, if one block
 * represented 64 bytes a maximally sized ALIST would represent
 * 128 gigabytes.
 *
 * A radix tree is used to maintain the bitmap and layed out in a manner
 * similar to the blist code.  Meta nodes use a radix of 16 and 2 bits per
 * block while leaf nodes use a radix of 32 and 1 bit per block (stored in
 * a 32 bit bitmap field).  Both meta and leaf nodes have a hint field.
 * This field gives us a hint as to the largest free contiguous range of
 * blocks under the node.  It may contain a value that is too high, but
 * will never contain a value that is too low.  When the radix tree is
 * searched, allocation failures in subtrees update the hint.
 *
 * The radix tree is layed out recursively using a linear array.  Each meta
 * node is immediately followed (layed out sequentially in memory) by
 * ALIST_META_RADIX lower level nodes.  This is a recursive structure but one
 * that can be easily scanned through a very simple 'skip' calculation.  In
 * order to support large radixes, portions of the tree may reside outside our
 * memory allocation.  We handle this with an early-terminate optimization
 * in the meta-node.  The memory allocation is only large enough to cover
 * the number of blocks requested at creation time even if it must be
 * encompassed in larger root-node radix.
 *
 * This code can be compiled stand-alone for debugging.
 */

#ifdef _KERNEL

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/kernel.h>
#include <sys/alist.h>
#include <sys/malloc.h>
#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>
#include <vm/vm_page.h>

#else

#ifndef ALIST_NO_DEBUG
#define ALIST_DEBUG
#endif

#include <sys/types.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>

#define kmalloc(a,b,c)	malloc(a)
#define kfree(a,b)	free(a)
#define kprintf		printf
#define KKASSERT(exp)	assert(exp)
struct malloc_type;

#include <sys/alist.h>

void panic(const char *ctl, ...);

#endif

/*
 * static support functions
 */

static alist_blk_t alst_leaf_alloc(almeta_t *scan, alist_blk_t blk,
				alist_blk_t start, alist_blk_t count);
static alist_blk_t alst_meta_alloc(almeta_t *scan, alist_blk_t blk,
				alist_blk_t start, alist_blk_t count,
				alist_blk_t radix, alist_blk_t skip);
static void alst_leaf_free(almeta_t *scan, alist_blk_t relblk,
				alist_blk_t count);
static void alst_meta_free(almeta_t *scan, alist_blk_t freeBlk,
				alist_blk_t count, alist_blk_t radix,
				alist_blk_t skip, alist_blk_t blk);
static alist_blk_t alst_radix_init(almeta_t *scan, alist_blk_t blk,
				alist_blk_t radix, alist_blk_t skip,
				alist_blk_t count);
#ifndef _KERNEL
static void	alst_radix_print(almeta_t *scan, alist_blk_t blk,
					alist_blk_t radix, alist_blk_t skip,
					int tab);
#endif

/*
 * Create a alist capable of handling up to the specified number of blocks.
 * Blocks must be greater then 0 but does not have to be a power of 2.
 *
 * The smallest alist consists of a single leaf node capable of
 * managing ALIST_BMAP_RADIX blocks.
 */
alist_t
alist_create(alist_blk_t blocks, struct malloc_type *mtype)
{
	alist_t bl;
	alist_blk_t radix;
	alist_blk_t skip = 0;

	/*
	 * Calculate radix and skip field used for scanning.
	 */
	radix = ALIST_BMAP_RADIX;

	while (radix < blocks) {
		radix *= ALIST_META_RADIX;
		skip = (skip + 1) * ALIST_META_RADIX;
	}

	bl = kmalloc(sizeof(struct alist), mtype, M_WAITOK | M_ZERO);

	bl->bl_blocks = blocks;
	bl->bl_radix = radix;
	bl->bl_skip = skip;
	bl->bl_rootblks = 1 + alst_radix_init(NULL, 0, bl->bl_radix,
					      bl->bl_skip, blocks);
	bl->bl_root = kmalloc(sizeof(almeta_t) * bl->bl_rootblks,
			      mtype, M_WAITOK);

#if defined(ALIST_DEBUG)
	kprintf(
		"ALIST representing %d blocks (%d MB of swap)"
		", requiring %dK (%d bytes) of ram\n",
		bl->bl_blocks,
		bl->bl_blocks * 4 / 1024,
		(bl->bl_rootblks * sizeof(almeta_t) + 1023) / 1024,
		(bl->bl_rootblks * sizeof(almeta_t))
	);
	kprintf("ALIST raw radix tree contains %d records\n", bl->bl_rootblks);
#endif
	alst_radix_init(bl->bl_root, 0, bl->bl_radix, bl->bl_skip, blocks);

	return(bl);
}

void
alist_init(alist_t bl, alist_blk_t blocks,
	   almeta_t *records, alist_blk_t nrecords)
{
	alist_blk_t radix;
	alist_blk_t skip = 0;

	/*
	 * Calculate radix and skip field used for scanning.
	 */
	radix = ALIST_BMAP_RADIX;

	while (radix < blocks) {
		radix *= ALIST_META_RADIX;
		skip = (skip + 1) * ALIST_META_RADIX;
	}
	bzero(bl, sizeof(*bl));

	bl->bl_blocks = blocks;
	bl->bl_radix = radix;
	bl->bl_skip = skip;
	bl->bl_rootblks = 1 + alst_radix_init(NULL, 0, bl->bl_radix,
					      bl->bl_skip, blocks);
	KKASSERT(bl->bl_rootblks <= nrecords);
	bl->bl_root = records;

#if defined(ALIST_DEBUG)
	kprintf(
		"ALIST representing %d blocks (%d MB of swap)"
		", requiring %dK (%d bytes) of ram\n",
		bl->bl_blocks,
		bl->bl_blocks * 4 / 1024,
		(bl->bl_rootblks * sizeof(almeta_t) + 1023) / 1024,
		(bl->bl_rootblks * sizeof(almeta_t))
	);
	kprintf("ALIST raw radix tree contains %d records\n", bl->bl_rootblks);
#endif
	alst_radix_init(bl->bl_root, 0, bl->bl_radix, bl->bl_skip, blocks);
}

void
alist_destroy(alist_t bl, struct malloc_type *mtype)
{
	kfree(bl->bl_root, mtype);
	kfree(bl, mtype);
}

/*
 * Reserve space in the block bitmap.  Return the base of a contiguous
 * region or ALIST_BLOCK_NONE if space could not be allocated.
 *
 * This nominally allocates a power-of-2 number of blocks.  However,
 * non-powers of 2 are accepted and implemented by first allocating
 * the nearest power of 2 and then freeing the remainder.
 */
alist_blk_t
alist_alloc(alist_t bl, alist_blk_t start, alist_blk_t count)
{
	alist_blk_t blk = ALIST_BLOCK_NONE;

	/*
	 * Check non power-of-2
	 */
	KKASSERT(count);
	if ((count | (count - 1)) != (count << 1) - 1) {
		alist_blk_t ncount = (count < 256) ? 1 : 256;
		while (ncount < count)
			ncount <<= 1;
		blk = alist_alloc(bl, start, ncount);
		if (blk != ALIST_BLOCK_NONE)
			alist_free(bl, blk + count, ncount - count);
		return (blk);
	}

	/*
	 * Power of 2
	 */
	if (bl && count < bl->bl_radix) {
		if (bl->bl_radix == ALIST_BMAP_RADIX) {
			blk = alst_leaf_alloc(bl->bl_root, 0, start, count);
		} else {
			blk = alst_meta_alloc(bl->bl_root, 0, start, count,
					      bl->bl_radix, bl->bl_skip);
		}
		if (blk != ALIST_BLOCK_NONE)
			bl->bl_free -= count;
	}
	return(blk);
}

/*
 * Free up space in the block bitmap.  The starting block and count do not
 * need to be power-of-2 aligned.  The related blocks must be in an allocated
 * state.
 */
void
alist_free(alist_t bl, alist_blk_t blkno, alist_blk_t count)
{
	if (bl) {
		KKASSERT(blkno + count <= bl->bl_blocks);
		if (bl->bl_radix == ALIST_BMAP_RADIX) {
			alst_leaf_free(bl->bl_root, blkno, count);
		} else {
			alst_meta_free(bl->bl_root, blkno, count,
				       bl->bl_radix, bl->bl_skip, 0);
		}
		bl->bl_free += count;
	}
}

/*
 * Returns the current total number of free blocks and the
 * approximate trailing largest contiguous free block available.
 */
alist_blk_t
alist_free_info(alist_t bl, alist_blk_t *startp, alist_blk_t *countp)
{
	alist_blk_t radix = bl->bl_radix;
	alist_blk_t skip = bl->bl_skip;
	alist_blk_t next_skip;
	alist_blk_t i;
	alist_bmap_t mask;
	almeta_t *scan = bl->bl_root;

	*startp = 0;
	*countp = 0;

	while (radix != ALIST_BMAP_RADIX) {
		radix /= ALIST_META_RADIX;
		next_skip = skip / ALIST_META_RADIX;

		/*
		 * Find the biggest fully allocated chunk.
		 */
		for (i = ALIST_META_RADIX - 1; i != ALIST_BLOCK_NONE; --i) {
			mask = (scan->bm_bitmap >> (i * 2)) & 3;
			if (mask == 0) {
				/*
				 * All allocated, continue the loop
				 */
				continue;
			}
			if (mask == 1) {
				/*
				 * Partially allocated, push into this guy
				 */
				break;
			}
			if (mask == 2) {
				/*
				 * Unknown state
				 */
				return(bl->bl_free);
			}
			/*
			 * All free, we can return the chunk.
			 */
			*startp += i * radix;
			*countp = radix;
			return(bl->bl_free);
		}

		/*
		 * If we failed to find anything stop here, otherwise push
		 * in.
		 */
		if (i == ALIST_BLOCK_NONE)
			return(bl->bl_free);
		*startp += i * radix;
		scan += 1 + next_skip * i;
		skip = next_skip - 1;
	}

	/*
	 * If we got all the way down to a leaf node locate the last block,
	 * power-of-2 aligned and power-of-2 sized.  Well, the easiest way
	 * to deal with this is to just return 1 block.
	 */
	if (radix == ALIST_BMAP_RADIX) {
		mask = scan->bm_bitmap;
		for (i = ALIST_BMAP_RADIX - 1; i != ALIST_BLOCK_NONE; --i) {
			if ((mask & ((alist_bmap_t)1U << i)))
				break;
		}

		/*
		 * did not find free entry
		 */
		if (i == ALIST_BLOCK_NONE)
			return(bl->bl_free);

		/*
		 * Return one block.
		 */
		*startp += i;
		*countp = 1;
		return(bl->bl_free);
	}
	return(bl->bl_free);
}

#ifdef ALIST_DEBUG

/*
 * alist_print()    - dump radix tree
 */

void
alist_print(alist_t bl)
{
	kprintf("ALIST {\n");
	alst_radix_print(bl->bl_root, 0, bl->bl_radix, bl->bl_skip, 4);
	kprintf("}\n");
}

#endif

/************************************************************************
 *			  ALLOCATION SUPPORT FUNCTIONS			*
 ************************************************************************
 *
 *	These support functions do all the actual work.  They may seem
 *	rather longish, but that's because I've commented them up.  The
 *	actual code is straight forward.
 *
 */

/*
 * alist_leaf_alloc() -	allocate at a leaf in the radix tree (a bitmap).
 *
 *	This is the core of the allocator and is optimized for the 1 block
 *	and the ALIST_BMAP_RADIX block allocation cases.  Other cases are
 *	somewhat slower.  The 1 block allocation case is log2 and extremely
 *	quick.
 *
 *	mask bit is 0  allocated, not available
 *	mask bit is 1  free, available for allocation
 */

static alist_blk_t
alst_leaf_alloc(almeta_t *scan, alist_blk_t blk, alist_blk_t start,
		alist_blk_t count)
{
	alist_bmap_t orig = scan->bm_bitmap;

	/*
	 * Allocate only beyond the start point.  Mask to 0 the low bits
	 * below start.  If start == blk no bits get cleared so don't
	 * bother.
	 */
	if (start >= blk + ALIST_BMAP_RADIX)
		return(ALIST_BLOCK_NONE);

	if (start > blk && start < blk + ALIST_BMAP_RADIX)
		orig &= ~(((alist_bmap_t)1U << (start - blk)) - 1);

	start &= ALIST_BMAP_RADIX - 1;

	/*
	 * Optimize bitmap all-allocated case.  Also, count = 1
	 * case assumes at least 1 bit is free in the bitmap, so
	 * we have to take care of this case here.
	 */
	if (orig == 0) {
		if (start <= blk)
			scan->bm_bighint = 0;
		return(ALIST_BLOCK_NONE);
	}

	/*
	 * Optimized code to allocate one bit out of the bitmap
	 */
	if (count == 1) {
		alist_bmap_t mask;
		alist_blk_t j = ALIST_BMAP_RADIX/2;
		alist_blk_t r = 0;

		mask = (alist_bmap_t)-1 >> (ALIST_BMAP_RADIX/2);

		while (j) {
			if ((orig & mask) == 0) {
			    r += j;
			    orig >>= j;
			}
			j >>= 1;
			mask >>= j;
		}
		scan->bm_bitmap &= ~(1 << r);
		return(blk + r);
	}

	/*
	 * non-optimized code to allocate N bits out of the bitmap.
	 * The more bits, the faster the code runs.  It will run
	 * the slowest allocating 2 bits, but since there aren't any
	 * memory ops in the core loop (or shouldn't be, anyway),
	 * you probably won't notice the difference.
	 *
	 * Similar to the blist case, the alist code also requires
	 * allocations to be power-of-2 sized and aligned to the
	 * size of the allocation, which simplifies the algorithm.
	 */
	{
		alist_blk_t j;
		alist_blk_t n = ALIST_BMAP_RADIX - count;
		alist_bmap_t mask;

		mask = (alist_bmap_t)-1 >> n;

		for (j = 0; j <= n; j += count) {
			if ((orig & mask) == mask) {
				scan->bm_bitmap &= ~mask;
				return(blk + j);
			}
			mask = mask << count;
		}
	}

	/*
	 * We couldn't allocate count in this subtree, update bighint
	 * if we were able to check the entire node.
	 */
	if (start <= blk)
		scan->bm_bighint = count - 1;
	return(ALIST_BLOCK_NONE);
}

/*
 * Attempt to allocate at a meta node.  If we can't, we update
 * bighint and return a failure.  Updating bighint optimize future
 * calls that hit this node.  We have to check for our collapse cases
 * and we have a few optimizations strewn in as well.
 */
static alist_blk_t
alst_meta_alloc(almeta_t *scan, alist_blk_t blk, alist_blk_t start,
		alist_blk_t count, alist_blk_t radix, alist_blk_t skip)
{
	alist_blk_t i;
	alist_bmap_t mask;
	alist_bmap_t pmask;
	alist_blk_t next_skip = ((u_int)skip / ALIST_META_RADIX);
	alist_blk_t orig_blk;

	/*
	 * ALL-ALLOCATED special case
	 */
	if (scan->bm_bitmap == 0)  {
		scan->bm_bighint = 0;
		return(ALIST_BLOCK_NONE);
	}

	radix /= ALIST_META_RADIX;

	/*
	 * Radix now represents each bitmap entry for this meta node.  If
	 * the number of blocks being allocated can be fully represented,
	 * we allocate directly out of this meta node.
	 *
	 * Meta node bitmaps use 2 bits per block.
	 *
	 *	00	ALL-ALLOCATED
	 *	01	PARTIALLY-FREE/PARTIALLY-ALLOCATED
	 *	10	(RESERVED)
	 *	11	ALL-FREE
	 */
	if (count >= radix) {
		alist_blk_t n = count / radix * 2;	/* number of bits */
		alist_blk_t j;

		mask = (alist_bmap_t)-1 >> (ALIST_BMAP_RADIX - n);
		for (j = 0; j < ALIST_META_RADIX; j += n / 2) {
			if ((scan->bm_bitmap & mask) == mask &&
			    blk + j * radix >= start) {
				scan->bm_bitmap &= ~mask;
				return(blk + j * radix);
			}
			mask <<= n;
		}
		if (scan->bm_bighint >= count && start <= blk)
			scan->bm_bighint = count >> 1;
		return(ALIST_BLOCK_NONE);
	}

	/*
	 * If not we have to recurse.
	 */
	mask = 0x00000003;
	pmask = 0x00000001;
	orig_blk = blk;
	for (i = 1; i <= skip; i += next_skip) {
		if (scan[i].bm_bighint == (alist_blk_t)-1) {
			/*
			 * Terminator
			 */
			break;
		}

		/*
		 * If the element is marked completely free (11), initialize
		 * the recursion.
		 */
		if ((scan->bm_bitmap & mask) == mask) {
			scan[i].bm_bitmap = (alist_bmap_t)-1;
			scan[i].bm_bighint = radix;
		}

		if ((scan->bm_bitmap & mask) == 0) {
			/*
			 * Object marked completely allocated, recursion
			 * contains garbage.
			 */
			/* Skip it */
		} else if (blk + radix <= start) {
			/*
			 * Object does not contain or is not beyond our
			 * start point.
			 */
			/* Skip it */
		} else if (count <= scan[i].bm_bighint) {
			/*
			 * count fits in object.  If successful and the
			 * deeper level becomes all allocated, mark our
			 * level as all-allocated.
			 */
			alist_blk_t r;
			if (next_skip == 1) {
				r = alst_leaf_alloc(&scan[i], blk, start,
						    count);
			} else {
				r = alst_meta_alloc(&scan[i], blk, start,
						    count,
						    radix, next_skip - 1);
			}
			if (r != ALIST_BLOCK_NONE) {
				if (scan[i].bm_bitmap == 0) {
					scan->bm_bitmap &= ~mask;
				} else {
					scan->bm_bitmap &= ~mask;
					scan->bm_bitmap |= pmask;
				}
				return(r);
			}
		}
		blk += radix;
		mask <<= 2;
		pmask <<= 2;
	}

	/*
	 * We couldn't allocate count in this subtree, update bighint
	 * if we were able to check the entire node.
	 */
	if (scan->bm_bighint >= count && start <= orig_blk)
		scan->bm_bighint = count >> 1;
	return(ALIST_BLOCK_NONE);
}

/*
 * Free allocated block from leaf bitmap
 */
static void
alst_leaf_free(almeta_t *scan, alist_blk_t blk, alist_blk_t count)
{
	/*
	 * free some data in this bitmap
	 *
	 * e.g.
	 *	0000111111111110000
	 *          \_________/\__/
	 *		v        n
	 */
	alist_blk_t n = blk & (ALIST_BMAP_RADIX - 1);
	alist_bmap_t mask;

	mask = ((alist_bmap_t)-1 << n) &
	    ((alist_bmap_t)-1 >> (ALIST_BMAP_RADIX - count - n));

	if (scan->bm_bitmap & mask)
		panic("%s: freeing free block", __func__);
	scan->bm_bitmap |= mask;

	/*
	 * We could probably do a better job here.  We are required to make
	 * bighint at least as large as the biggest contiguous block of
	 * data.  If we just shoehorn it, a little extra overhead will
	 * be incured on the next allocation (but only that one typically).
	 */
	scan->bm_bighint = ALIST_BMAP_RADIX;
}

/*
 * Free allocated blocks from radix tree meta info.   This support routine
 * frees a range of blocks from the bitmap.  The range must be entirely
 * enclosed by this radix node.  If a meta node, we break the range down
 * recursively to free blocks in subnodes (which means that this code
 * can free an arbitrary range whereas the allocation code cannot allocate
 * an arbitrary range).
 */
static void
alst_meta_free(almeta_t *scan, alist_blk_t freeBlk, alist_blk_t count,
	       alist_blk_t radix, alist_blk_t skip, alist_blk_t blk)
{
	alist_blk_t next_skip = ((u_int)skip / ALIST_META_RADIX);
	alist_bmap_t mask;
	alist_bmap_t pmask;
	alist_blk_t i;

	/*
	 * Break the free down into its components.  Because it is so easy
	 * to implement, frees are not limited to power-of-2 sizes.
	 *
	 * Each block in a meta-node bitmap takes two bits.
	 */
	radix /= ALIST_META_RADIX;

	i = (freeBlk - blk) / radix;
	blk += i * radix;
	mask = 0x00000003 << (i * 2);
	pmask = 0x00000001 << (i * 2);

	i = i * next_skip + 1;

	while (i <= skip && blk < freeBlk + count) {
		alist_blk_t v;

		v = blk + radix - freeBlk;
		if (v > count)
			v = count;

		if (scan->bm_bighint == (alist_blk_t)-1)
			panic("%s: freeing unexpected range", __func__);

		/*
		 * WARNING on bighint updates.  When we free an element in
		 * a chunk if the chunk becomes wholely free it is possible
		 * that the whole node is now free, so bighint must be set
		 * to cover the whole node.  Otherwise address-specific
		 * allocations may fail.
		 *
		 * We don't bother figuring out how much of the node is
		 * actually free in this case.
		 */
		if (freeBlk == blk && count >= radix) {
			/*
			 * The area being freed covers the entire block,
			 * assert that we are marked all-allocated and
			 * then mark it all-free.
			 */
			KKASSERT((scan->bm_bitmap & mask) == 0);
			scan->bm_bitmap |= mask;
			scan->bm_bighint = radix * ALIST_META_RADIX;
		} else {
			/*
			 * If we were previously marked all-allocated, fix-up
			 * the next layer so we can recurse down into it.
			 */
			if ((scan->bm_bitmap & mask) == 0) {
				scan[i].bm_bitmap = (alist_bmap_t)0;
				scan[i].bm_bighint = 0;
			}

			/*
			 * Recursion case, then either mark all-free or
			 * partially free.
			 */
			if (next_skip == 1) {
				alst_leaf_free(&scan[i], freeBlk, v);
			} else {
				alst_meta_free(&scan[i], freeBlk, v,
					       radix, next_skip - 1, blk);
			}
			if (scan[i].bm_bitmap == (alist_bmap_t)-1) {
				scan->bm_bitmap |= mask;
				scan->bm_bighint = radix * ALIST_META_RADIX;
			} else {
				scan->bm_bitmap &= ~mask;
				scan->bm_bitmap |= pmask;
				if (scan->bm_bighint < scan[i].bm_bighint)
				    scan->bm_bighint = scan[i].bm_bighint;
			}
		}
		mask <<= 2;
		pmask <<= 2;
		count -= v;
		freeBlk += v;
		blk += radix;
		i += next_skip;
	}
}

/*
 * Initialize our meta structures and bitmaps and calculate the exact
 * amount of space required to manage 'count' blocks - this space may
 * be considerably less then the calculated radix due to the large
 * RADIX values we use.
 */
static alist_blk_t
alst_radix_init(almeta_t *scan, alist_blk_t blk, alist_blk_t radix,
		alist_blk_t skip, alist_blk_t count)
{
	alist_blk_t i;
	alist_blk_t next_skip;
	alist_bmap_t mask;
	alist_bmap_t pmask;
	alist_blk_t memindex;

	/*
	 * Leaf node
	 */
	if (radix == ALIST_BMAP_RADIX) {
		if (scan) {
			scan->bm_bighint = 0;
			scan->bm_bitmap = 0;
		}
		return(0);
	}

	/*
	 * Meta node.  If allocating the entire object we can special
	 * case it.  However, we need to figure out how much memory
	 * is required to manage 'count' blocks, so we continue on anyway.
	 */
	if (scan) {
		scan->bm_bighint = 0;
		scan->bm_bitmap = 0;
	}
	memindex = 0;

	radix /= ALIST_META_RADIX;
	next_skip = skip / ALIST_META_RADIX;
	mask = 0x00000003;
	pmask = 0x00000001;

	for (i = 1; i <= skip; i += next_skip) {
		if (count >= blk + radix) {
			/*
			 * Allocate the entire object
			 */
			memindex += alst_radix_init(((scan) ? &scan[i] : NULL),
						    blk, radix,
						    next_skip - 1, count);
			/* already marked as wholely allocated */
		} else if (count > blk) {
			/*
			 * Allocate a partial object, well it's really
			 * all-allocated, we just aren't allowed to
			 * free the whole thing.
			 */
			memindex += alst_radix_init(((scan) ? &scan[i] : NULL),
						    blk, radix,
						    next_skip - 1, count);
			/* already marked as wholely allocated */
		} else {
			/*
			 * Add terminator but continue the loop.  Populate
			 * all terminators.
			 */
			if (scan) {
				scan[i].bm_bighint = (alist_blk_t)-1;
				scan[i].bm_bitmap = 0;
			}
			/* already marked as wholely allocated */
		}
		mask <<= 2;
		pmask <<= 2;
		blk += radix;
	}
	memindex += ALIST_META_RADIX;
	return(memindex);
}

#ifdef ALIST_DEBUG

static void
alst_radix_print(almeta_t *scan, alist_blk_t blk, alist_blk_t radix,
		 alist_blk_t skip, int tab)
{
	alist_blk_t i;
	alist_blk_t next_skip;
	alist_bmap_t mask;

	if (radix == ALIST_BMAP_RADIX) {
		kprintf(
		    "%*.*s(%04x,%d): bitmap %08x big=%d\n",
		    tab, tab, "",
		    blk, radix,
		    scan->bm_bitmap,
		    scan->bm_bighint
		);
		return;
	}

	if (scan->bm_bitmap == 0) {
		kprintf(
		    "%*.*s(%04x,%d) ALL ALLOCATED\n",
		    tab, tab, "",
		    blk,
		    radix
		);
		return;
	}
	if (scan->bm_bitmap == (alist_bmap_t)-1) {
		kprintf(
		    "%*.*s(%04x,%d) ALL FREE\n",
		    tab, tab, "",
		    blk,
		    radix
		);
		return;
	}

	kprintf(
	    "%*.*s(%04x,%d): subtree (%d) bitmap=%08x big=%d {\n",
	    tab, tab, "",
	    blk, radix,
	    radix,
	    scan->bm_bitmap,
	    scan->bm_bighint
	);

	radix /= ALIST_META_RADIX;
	next_skip = skip / ALIST_META_RADIX;
	tab += 4;
	mask = 0x00000003;

	for (i = 1; i <= skip; i += next_skip) {
		if (scan[i].bm_bighint == (alist_blk_t)-1) {
			kprintf(
			    "%*.*s(%04x,%d): Terminator\n",
			    tab, tab, "",
			    blk, radix
			);
			break;
		}
		if ((scan->bm_bitmap & mask) == mask) {
			kprintf(
			    "%*.*s(%04x,%d): ALL FREE\n",
			    tab, tab, "",
			    blk, radix
			);
		} else if ((scan->bm_bitmap & mask) == 0) {
			kprintf(
			    "%*.*s(%04x,%d): ALL ALLOCATED\n",
			    tab, tab, "",
			    blk, radix
			);
		} else {
			alst_radix_print(
			    &scan[i],
			    blk,
			    radix,
			    next_skip - 1,
			    tab
			);
		}
		blk += radix;
		mask <<= 2;
	}
	tab -= 4;

	kprintf("%*.*s}\n", tab, tab, "");
}

#endif

#ifdef ALIST_DEBUG

int
main(int ac, char **av)
{
	alist_blk_t size = 1024;
	alist_blk_t da = 0;
	alist_blk_t count = 0;
	alist_t bl;
	int i;

	for (i = 1; i < ac; ++i) {
		const char *ptr = av[i];
		if (*ptr != '-') {
			size = strtol(ptr, NULL, 0);
			continue;
		}
		ptr += 2;
		fprintf(stderr, "Bad option: %s\n", ptr - 2);
		exit(1);
	}
	bl = alist_create(size, NULL);
	alist_free(bl, 0, size);

	for (;;) {
		char buf[1024];
		alist_blk_t bfree;


		kprintf("%d/%d/%d> ", bl->bl_free, size, bl->bl_radix);
		fflush(stdout);
		if (fgets(buf, sizeof(buf), stdin) == NULL)
			break;
		switch(buf[0]) {
		case 'p':
			alist_print(bl);
			break;
		case 'a':
			if (sscanf(buf + 1, "%x %d", &da, &count) == 2) {
				da = alist_alloc(bl, da, count);
				kprintf("    R=%04x\n", da);
			} else if (sscanf(buf + 1, "%d", &count) == 1) {
				da =  alist_alloc(bl, 0, count);
				kprintf("    R=%04x\n", da);
			} else if (count) {
				kprintf("alloc 0x%04x/%d\n", da, count);
				alist_blk_t blk = alist_alloc(bl, da, count);
				kprintf("    R=%04x\n", blk);
			} else {
				kprintf("?\n");
			}
			break;
		case 'f':
			if (sscanf(buf + 1, "%x %d", &da, &count) == 2) {
				alist_free(bl, da, count);
			} else if (count) {
				kprintf("free 0x%04x/%d\n", da, count);
				alist_free(bl, da, count);
			} else {
				kprintf("?\n");
			}
			break;
		case '?':
		case 'h':
			puts("p          -print\n"
			     "a %d       -allocate\n"
			     "f %x %d    -free\n"
			     "h/?        -help");
			break;
		case 'i':
			bfree = alist_free_info(bl, &da, &count);
			kprintf("info: %d free trailing: 0x%04x/%d\n",
				bfree, da, count);
			break;
		default:
			kprintf("?\n");
			break;
		}
	}
	return(0);
}

void
panic(const char *ctl, ...)
{
	__va_list va;

	__va_start(va, ctl);
	vfprintf(stderr, ctl, va);
	fprintf(stderr, "\n");
	__va_end(va);
	exit(1);
}

#endif