mtree/BSD.root.dist: Use spaces.

[dragonfly.git] / sys / kern / subr_alist.c

/*
 * 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("alst_radix_free: freeing free block");
        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("alst_meta_free: freeing unexpected range");

                /*
                 * 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