lib/libstand/zalloc.c

   1 /*
   2  * This module derived from code donated to the FreeBSD Project by
   3  * Matthew Dillon <dillon@backplane.com>
   4  *
   5  * Copyright (c) 1998 The FreeBSD Project
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * $FreeBSD: src/lib/libstand/zalloc.c,v 1.5.2.1 2002/12/28 18:04:15 dillon Exp $
  30  * $DragonFly: src/lib/libstand/zalloc.c,v 1.2 2003/06/17 04:26:51 dillon Exp $
  31  */
  32
  33 /*
  34  * LIB/MEMORY/ZALLOC.C  - self contained low-overhead memory pool/allocation
  35  *                        subsystem
  36  *
  37  *      This subsystem implements memory pools and memory allocation
  38  *      routines.
  39  *
  40  *      Pools are managed via a linked list of 'free' areas.  Allocating
  41  *      memory creates holes in the freelist, freeing memory fills them.
  42  *      Since the freelist consists only of free memory areas, it is possible
  43  *      to allocate the entire pool without incuring any structural overhead.
  44  *
  45  *      The system works best when allocating similarly-sized chunks of
  46  *      memory.  Care must be taken to avoid fragmentation when
  47  *      allocating/deallocating dissimilar chunks.
  48  *
  49  *      When a memory pool is first allocated, the entire pool is marked as
  50  *      allocated.  This is done mainly because we do not want to modify any
  51  *      portion of a pool's data area until we are given permission.  The
  52  *      caller must explicitly deallocate portions of the pool to make them
  53  *      available.
  54  *
  55  *      z[n]xalloc() works like z[n]alloc() but the allocation is made from
  56  *      within the specified address range.  If the segment could not be
  57  *      allocated, NULL is returned.  WARNING!  The address range will be
  58  *      aligned to an 8 or 16 byte boundry depending on the cpu so if you
  59  *      give an unaligned address range, unexpected results may occur.
  60  *
  61  *      If a standard allocation fails, the reclaim function will be called
  62  *      to recover some space.  This usually causes other portions of the
  63  *      same pool to be released.  Memory allocations at this low level
  64  *      should not block but you can do that too in your reclaim function
  65  *      if you want.  Reclaim does not function when z[n]xalloc() is used,
  66  *      only for z[n]alloc().
  67  *
  68  *      Allocation and frees of 0 bytes are valid operations.
  69  */
  70
  71 #include "zalloc_defs.h"
  72
  73 /*
  74  * znalloc() -  allocate memory (without zeroing) from pool.  Call reclaim
  75  *              and retry if appropriate, return NULL if unable to allocate
  76  *              memory.
  77  */
  78
  79 void *
  80 znalloc(MemPool *mp, uintptr_t bytes)
  81 {
  82     /*
  83      * align according to pool object size (can be 0).  This is
  84      * inclusive of the MEMNODE_SIZE_MASK minimum alignment.
  85      *
  86      */
  87     bytes = (bytes + MEMNODE_SIZE_MASK) & ~MEMNODE_SIZE_MASK;
  88
  89     if (bytes == 0)
  90         return((void *)-1);
  91
  92     /*
  93      * locate freelist entry big enough to hold the object.  If all objects
  94      * are the same size, this is a constant-time function.
  95      */
  96
  97     if (bytes <= mp->mp_Size - mp->mp_Used) {
  98         MemNode **pmn;
  99         MemNode *mn;
 100
 101         for (pmn = &mp->mp_First; (mn=*pmn) != NULL; pmn = &mn->mr_Next) {
 102             if (bytes > mn->mr_Bytes)
 103                 continue;
 104
 105             /*
 106              *  Cut a chunk of memory out of the beginning of this
 107              *  block and fixup the link appropriately.
 108              */
 109
 110             {
 111                 char *ptr = (char *)mn;
 112
 113                 if (mn->mr_Bytes == bytes) {
 114                     *pmn = mn->mr_Next;
 115                 } else {
 116                     mn = (MemNode *)((char *)mn + bytes);
 117                     mn->mr_Next  = ((MemNode *)ptr)->mr_Next;
 118                     mn->mr_Bytes = ((MemNode *)ptr)->mr_Bytes - bytes;
 119                     *pmn = mn;
 120                 }
 121                 mp->mp_Used += bytes;
 122                 return(ptr);
 123             }
 124         }
 125     }
 126
 127     /*
 128      * Memory pool is full, return NULL.
 129      */
 130
 131     return(NULL);
 132 }
 133
 134 /*
 135  * zfree() - free previously allocated memory
 136  */
 137
 138 void
 139 zfree(MemPool *mp, void *ptr, uintptr_t bytes)
 140 {
 141     /*
 142      * align according to pool object size (can be 0).  This is
 143      * inclusive of the MEMNODE_SIZE_MASK minimum alignment.
 144      */
 145     bytes = (bytes + MEMNODE_SIZE_MASK) & ~MEMNODE_SIZE_MASK;
 146
 147     if (bytes == 0)
 148         return;
 149
 150     /*
 151      * panic if illegal pointer
 152      */
 153
 154     if ((char *)ptr < (char *)mp->mp_Base ||
 155         (char *)ptr + bytes > (char *)mp->mp_End ||
 156         ((uintptr_t)ptr & MEMNODE_SIZE_MASK) != 0)
 157         panic("zfree(%p,%d): wild pointer", ptr, bytes);
 158
 159     /*
 160      * free the segment
 161      */
 162
 163     {
 164         MemNode **pmn;
 165         MemNode *mn;
 166
 167         mp->mp_Used -= bytes;
 168
 169         for (pmn = &mp->mp_First; (mn = *pmn) != NULL; pmn = &mn->mr_Next) {
 170             /*
 171              * If area between last node and current node
 172              *  - check range
 173              *  - check merge with next area
 174              *  - check merge with previous area
 175              */
 176             if ((char *)ptr <= (char *)mn) {
 177                 /*
 178                  * range check
 179                  */
 180                 if ((char *)ptr + bytes > (char *)mn)
 181                     panic("zfree(%p,%d): corrupt memlist1",ptr, bytes);
 182
 183                 /*
 184                  * merge against next area or create independant area
 185                  */
 186
 187                 if ((char *)ptr + bytes == (char *)mn) {
 188                     ((MemNode *)ptr)->mr_Next = mn->mr_Next;
 189                     ((MemNode *)ptr)->mr_Bytes= bytes + mn->mr_Bytes;
 190                 } else {
 191                     ((MemNode *)ptr)->mr_Next = mn;
 192                     ((MemNode *)ptr)->mr_Bytes= bytes;
 193                 }
 194                 *pmn = mn = (MemNode *)ptr;
 195
 196                 /*
 197                  * merge against previous area (if there is a previous
 198                  * area).
 199                  */
 200
 201                 if (pmn != &mp->mp_First) {
 202                     if ((char*)pmn + ((MemNode*)pmn)->mr_Bytes == (char*)ptr) {
 203                         ((MemNode *)pmn)->mr_Next = mn->mr_Next;
 204                         ((MemNode *)pmn)->mr_Bytes += mn->mr_Bytes;
 205                         mn = (MemNode *)pmn;
 206                     }
 207                 }
 208                 return;
 209                 /* NOT REACHED */
 210             }
 211             if ((char *)ptr < (char *)mn + mn->mr_Bytes)
 212                 panic("zfree(%p,%d): corrupt memlist2", ptr, bytes);
 213         }
 214         /*
 215          * We are beyond the last MemNode, append new MemNode.  Merge against
 216          * previous area if possible.
 217          */
 218         if (pmn == &mp->mp_First ||
 219             (char *)pmn + ((MemNode *)pmn)->mr_Bytes != (char *)ptr
 220         ) {
 221             ((MemNode *)ptr)->mr_Next = NULL;
 222             ((MemNode *)ptr)->mr_Bytes = bytes;
 223             *pmn = (MemNode *)ptr;
 224             mn = (MemNode *)ptr;
 225         } else {
 226             ((MemNode *)pmn)->mr_Bytes += bytes;
 227             mn = (MemNode *)pmn;
 228         }
 229     }
 230 }
 231
 232 /*
 233  * zextendPool() - extend memory pool to cover additional space.
 234  *
 235  *                 Note: the added memory starts out as allocated, you
 236  *                 must free it to make it available to the memory subsystem.
 237  *
 238  *                 Note: mp_Size may not reflect (mp_End - mp_Base) range
 239  *                 due to other parts of the system doing their own sbrk()
 240  *                 calls.
 241  */
 242
 243 void
 244 zextendPool(MemPool *mp, void *base, uintptr_t bytes)
 245 {
 246     if (mp->mp_Size == 0) {
 247         mp->mp_Base = base;
 248         mp->mp_Used = bytes;
 249         mp->mp_End = (char *)base + bytes;
 250         mp->mp_Size = bytes;
 251     } else {
 252         void *pend = (char *)mp->mp_Base + mp->mp_Size;
 253
 254         if (base < mp->mp_Base) {
 255             mp->mp_Size += (char *)mp->mp_Base - (char *)base;
 256             mp->mp_Used += (char *)mp->mp_Base - (char *)base;
 257             mp->mp_Base = base;
 258         }
 259         base = (char *)base + bytes;
 260         if (base > pend) {
 261             mp->mp_Size += (char *)base - (char *)pend;
 262             mp->mp_Used += (char *)base - (char *)pend;
 263             mp->mp_End = (char *)base;
 264         }
 265     }
 266 }
 267
 268 #ifdef ZALLOCDEBUG
 269
 270 void
 271 zallocstats(MemPool *mp)
 272 {
 273     int abytes = 0;
 274     int hbytes = 0;
 275     int fcount = 0;
 276     MemNode *mn;
 277
 278     printf("%d bytes reserved", (int) mp->mp_Size);
 279
 280     mn = mp->mp_First;
 281
 282     if ((void *)mn != (void *)mp->mp_Base) {
 283         abytes += (char *)mn - (char *)mp->mp_Base;
 284     }
 285
 286     while (mn) {
 287         if ((char *)mn + mn->mr_Bytes != mp->mp_End) {
 288             hbytes += mn->mr_Bytes;
 289             ++fcount;
 290         }
 291         if (mn->mr_Next)
 292             abytes += (char *)mn->mr_Next - ((char *)mn + mn->mr_Bytes);
 293         mn = mn->mr_Next;
 294     }
 295     printf(" %d bytes allocated\n%d fragments (%d bytes fragmented)\n",
 296         abytes,
 297         fcount,
 298         hbytes
 299     );
 300 }
 301
 302 #endif
 303