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0001 /*
0002  * Copyright (C) 1998-2000 Netscape Communications Corporation.
0003  *
0004  * Other contributors:
0005  *   Nick Blievers <nickb@adacel.com.au>
0006  *   Jeff Hostetler <jeff@nerdone.com>
0007  *   Tom Rini <trini@kernel.crashing.org>
0008  *   Raffaele Sena <raff@netwinder.org>
0009  *
0010  * This library is free software; you can redistribute it and/or
0011  * modify it under the terms of the GNU Lesser General Public
0012  * License as published by the Free Software Foundation; either
0013  * version 2.1 of the License, or (at your option) any later version.
0014  *
0015  * This library is distributed in the hope that it will be useful,
0016  * but WITHOUT ANY WARRANTY; without even the implied warranty of
0017  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
0018  * Lesser General Public License for more details.
0019  *
0020  * You should have received a copy of the GNU Lesser General Public
0021  * License along with this library; if not, write to the Free Software
0022  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
0023  *
0024  * Alternatively, the contents of this file may be used under the terms
0025  * of either the Mozilla Public License Version 1.1, found at
0026  * http://www.mozilla.org/MPL/ (the "MPL") or the GNU General Public
0027  * License Version 2.0, found at http://www.fsf.org/copyleft/gpl.html
0028  * (the "GPL"), in which case the provisions of the MPL or the GPL are
0029  * applicable instead of those above.  If you wish to allow use of your
0030  * version of this file only under the terms of one of those two
0031  * licenses (the MPL or the GPL) and not to allow others to use your
0032  * version of this file under the LGPL, indicate your decision by
0033  * deletingthe provisions above and replace them with the notice and
0034  * other provisions required by the MPL or the GPL, as the case may be.
0035  * If you do not delete the provisions above, a recipient may use your
0036  * version of this file under any of the LGPL, the MPL or the GPL.
0037  */
0038 
0039 /*
0040  * Lifetime-based fast allocation, inspired by much prior art, including
0041  * "Fast Allocation and Deallocation of Memory Based on Object Lifetimes"
0042  * David R. Hanson, Software -- Practice and Experience, Vol. 20(1).
0043  */
0044 
0045 #include "arena.h"
0046 
0047 #include <stdlib.h>
0048 #include <string.h>
0049 
0050 #if HAVE_GETPAGESIZE
0051 #include <unistd.h>
0052 #define POOL_SIZE qMax(8192u, 2*( unsigned ) getpagesize())
0053 #else
0054 #define POOL_SIZE 8192
0055 #endif
0056 
0057 //#define DEBUG_ARENA_MALLOC
0058 #ifdef DEBUG_ARENA_MALLOC
0059 #include <assert.h>
0060 #include <stdio.h>
0061 #endif
0062 
0063 namespace khtml
0064 {
0065 
0066 #ifdef DEBUG_ARENA_MALLOC
0067 static int i = 0;
0068 #endif
0069 
0070 #define FREELIST_MAX 50
0071 #define LARGE_ALLOCATION_CEIL(pool) (pool)->arenasize * 256
0072 #define MAX_DISCRETE_ALLOCATION(pool) (pool)->arenasize * 64
0073 static Arena *arena_freelist = nullptr;
0074 static int freelist_count = 0;
0075 
0076 #define ARENA_DEFAULT_ALIGN  sizeof(double)
0077 #define BIT(n)               ((unsigned int)1 << (n))
0078 #define BITMASK(n)           (BIT(n) - 1)
0079 #define CEILING_LOG2(_log2,_n)   \
0080     unsigned int j_ = (unsigned int)(_n);   \
0081     (_log2) = 0;                    \
0082     if ((j_) & ((j_)-1))            \
0083         (_log2) += 1;               \
0084     if ((j_) >> 16)                 \
0085         (_log2) += 16, (j_) >>= 16; \
0086     if ((j_) >> 8)                  \
0087         (_log2) += 8, (j_) >>= 8;   \
0088     if ((j_) >> 4)                  \
0089         (_log2) += 4, (j_) >>= 4;   \
0090     if ((j_) >> 2)                  \
0091         (_log2) += 2, (j_) >>= 2;   \
0092     if ((j_) >> 1)                  \
0093         (_log2) += 1;
0094 
0095 int CeilingLog2(unsigned int i)
0096 {
0097     int log2;
0098     CEILING_LOG2(log2, i);
0099     return log2;
0100 }
0101 
0102 void InitArenaPool(ArenaPool *pool, const char * /*name*/,
0103                    unsigned int /*size*/, unsigned int align)
0104 {
0105     unsigned int size = POOL_SIZE;
0106     if (align == 0) {
0107         align = ARENA_DEFAULT_ALIGN;
0108     }
0109     pool->mask = BITMASK(CeilingLog2(align));
0110     pool->first.next = nullptr;
0111     pool->first.base = pool->first.avail = pool->first.limit =
0112             (uword)ARENA_ALIGN(pool, &pool->first + 1);
0113     pool->current = &pool->first;
0114     pool->arenasize = size;
0115     pool->largealloc = LARGE_ALLOCATION_CEIL(pool);
0116     pool->cumul = freelist_count * size;
0117 }
0118 
0119 /*
0120  ** ArenaAllocate() -- allocate space from an arena pool
0121  **
0122  ** Description: ArenaAllocate() allocates space from an arena
0123  ** pool.
0124  **
0125  ** First try to satisfy the request from arenas starting at
0126  ** pool->current.
0127  **
0128  ** If there is not enough space in the arena pool->current, try
0129  ** to claim an arena, on a first fit basis, from the global
0130  ** freelist (arena_freelist).
0131  **
0132  ** If no arena in arena_freelist is suitable, then try to
0133  ** allocate a new arena from the heap.
0134  **
0135  ** Returns: pointer to allocated space or NULL
0136  **
0137  */
0138 void *ArenaAllocate(ArenaPool *pool, unsigned int nb)
0139 {
0140     Arena *a;
0141     char *rp;     /* returned pointer */
0142 
0143 #ifdef DEBUG_ARENA_MALLOC
0144     assert((nb & pool->mask) == 0);
0145 #endif
0146 
0147     nb = (uword)ARENA_ALIGN(pool, nb); /* force alignment */
0148 
0149     /* attempt to allocate from arenas at pool->current */
0150     {
0151         a = pool->current;
0152         do {
0153             if (a->avail + nb <= a->limit)  {
0154                 pool->current = a;
0155                 rp = (char *)a->avail;
0156                 a->avail += nb;
0157                 VALGRIND_MEMPOOL_ALLOC(a->base, rp, nb);
0158                 return rp;
0159             }
0160         } while (nullptr != (a = a->next));
0161     }
0162 
0163     /* attempt to allocate from arena_freelist */
0164     {
0165         Arena *p; /* previous pointer, for unlinking from freelist */
0166 
0167         for (a = p = arena_freelist; a != nullptr; p = a, a = a->next) {
0168             if (a->base + nb <= a->limit)  {
0169                 if (p == arena_freelist) {
0170                     arena_freelist = a->next;
0171                 } else {
0172                     p->next = a->next;
0173                 }
0174                 a->avail = a->base;
0175                 rp = (char *)a->avail;
0176                 a->avail += nb;
0177                 VALGRIND_MEMPOOL_ALLOC(a->base, rp, nb);
0178                 /* the newly allocated arena is linked after pool->current
0179                  *  and becomes pool->current */
0180                 a->next = pool->current->next;
0181                 pool->current->next = a;
0182                 pool->current = a;
0183                 if (nullptr == pool->first.next) {
0184                     pool->first.next = a;
0185                 }
0186                 freelist_count--;
0187                 return (rp);
0188             }
0189         }
0190     }
0191 
0192     /* attempt to allocate from the heap */
0193     {
0194         unsigned int sz;
0195 #if HAVE_MMAP
0196         if (pool->cumul > pool->largealloc) {
0197             // High memory pressure. Switch to a fractional allocation strategy
0198             // so that malloc gets a chance to successfully trim us down when it's over.
0199             sz = qMin(pool->cumul / 12, MAX_DISCRETE_ALLOCATION(pool));
0200 #ifdef DEBUG_ARENA_MALLOC
0201             printf("allocating %d bytes (fractional strategy)\n", sz);
0202 #endif
0203         } else
0204 #endif
0205             sz = pool->arenasize > nb ? pool->arenasize : nb;
0206         sz += sizeof * a + pool->mask; /* header and alignment slop */
0207         pool->cumul += sz;
0208 #ifdef DEBUG_ARENA_MALLOC
0209         i++;
0210         printf("Malloc: %d\n", i);
0211 #endif
0212         a = (Arena *)malloc(sz);
0213         if (a)  {
0214             a->limit = (uword)a + sz;
0215             a->base = a->avail = (uword)ARENA_ALIGN(pool, a + 1);
0216             VALGRIND_CREATE_MEMPOOL(a->base, 0, 0);
0217             rp = (char *)a->avail;
0218             a->avail += nb;
0219             VALGRIND_MEMPOOL_ALLOC(a->base, rp, nb);
0220 
0221             /* the newly allocated arena is linked after pool->current
0222             *  and becomes pool->current */
0223             a->next = pool->current->next;
0224             pool->current->next = a;
0225             pool->current = a;
0226             if (!pool->first.next) {
0227                 pool->first.next = a;
0228             }
0229             return (rp);
0230         }
0231     }
0232 
0233     /* we got to here, and there's no memory to allocate */
0234     return (nullptr);
0235 } /* --- end ArenaAllocate() --- */
0236 
0237 /*
0238  * Free tail arenas linked after head, which may not be the true list head.
0239  * Reset pool->current to point to head in case it pointed at a tail arena.
0240  */
0241 static void FreeArenaList(ArenaPool *pool, Arena *head, bool reallyFree)
0242 {
0243     Arena **ap, *a;
0244 
0245     ap = &head->next;
0246     a = *ap;
0247     if (!a) {
0248         return;
0249     }
0250 
0251 #ifdef DEBUG_ARENA_MALLOC
0252     printf("****** Freeing arena pool. Total allocated memory: %d\n", pool->cumul);
0253 
0254     do {
0255         assert(a->base <= a->avail && a->avail <= a->limit);
0256         a->avail = a->base;
0257         CLEAR_UNUSED(a);
0258     } while ((a = a->next) != 0);
0259     a = *ap;
0260 #endif
0261 
0262     if (freelist_count >= FREELIST_MAX) {
0263         reallyFree = true;
0264     }
0265 
0266     if (reallyFree) {
0267         do {
0268             *ap = a->next;
0269             VALGRIND_DESTROY_MEMPOOL(a->base);
0270             CLEAR_ARENA(a);
0271 #ifdef DEBUG_ARENA_MALLOC
0272             if (a) {
0273                 i--;
0274                 printf("Free: %d\n", i);
0275             }
0276 #endif
0277             free(a); a = nullptr;
0278         } while ((a = *ap) != nullptr);
0279     } else {
0280         /* Insert as much of the arena chain as we can hold at the front of the freelist. */
0281         do {
0282             ap = &(*ap)->next;
0283             freelist_count++;
0284         } while (*ap && freelist_count < FREELIST_MAX);
0285 
0286         /* Get rid of excess */
0287         if (*ap) {
0288             Arena *xa, *n;
0289             for (xa = *ap; xa; xa = n) {
0290                 VALGRIND_DESTROY_MEMPOOL(xa->base);
0291                 n = xa->next;
0292 #ifdef DEBUG_ARENA_MALLOC
0293                 i--;
0294                 printf("Free: %d\n", i);
0295 #endif
0296                 CLEAR_ARENA(xa);
0297                 free(xa);
0298             }
0299         }
0300         *ap = arena_freelist;
0301         arena_freelist = a;
0302         head->next = nullptr;
0303     }
0304     pool->current = head;
0305 }
0306 
0307 void ArenaRelease(ArenaPool *pool, char *mark)
0308 {
0309     Arena *a;
0310 
0311     for (a = pool->first.next; a; a = a->next) {
0312         if (UPTRDIFF(mark, a->base) < UPTRDIFF(a->avail, a->base)) {
0313             a->avail = (uword)ARENA_ALIGN(pool, mark);
0314             FreeArenaList(pool, a, false);
0315             return;
0316         }
0317     }
0318 }
0319 
0320 void FreeArenaPool(ArenaPool *pool)
0321 {
0322     FreeArenaList(pool, &pool->first, false);
0323 }
0324 
0325 void FinishArenaPool(ArenaPool *pool)
0326 {
0327     FreeArenaList(pool, &pool->first, true);
0328 }
0329 
0330 void ArenaFinish()
0331 {
0332     Arena *a, *next;
0333 #ifdef DEBUG_ARENA_MALLOC
0334     printf("releasing global Arena freelist\n");
0335 #endif
0336     for (a = arena_freelist; a; a = next) {
0337         next = a->next;
0338         free(a); a = nullptr;
0339     }
0340     freelist_count = 0;
0341     arena_freelist = nullptr;
0342 }
0343 
0344 } // namespace