summaryrefslogtreecommitdiffstats
path: root/khtml/misc/arena.cpp
blob: 5efcaf98dfeb52648a0cbd62be51cf629e88aa60 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
/*
 * Copyright (C) 1998-2000 Netscape Communications Corporation.
 *
 * Other contributors:
 *   Nick Blievers <nickb@adacel.com.au>
 *   Jeff Hostetler <jeff@nerdone.com>
 *   Tom Rini <trini@kernel.crashing.org>
 *   Raffaele Sena <raff@netwinder.org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Alternatively, the contents of this file may be used under the terms
 * of either the Mozilla Public License Version 1.1, found at
 * http://www.mozilla.org/MPL/ (the "MPL") or the GNU General Public
 * License Version 2.0, found at http://www.fsf.org/copyleft/gpl.html
 * (the "GPL"), in which case the provisions of the MPL or the GPL are
 * applicable instead of those above.  If you wish to allow use of your
 * version of this file only under the terms of one of those two
 * licenses (the MPL or the GPL) and not to allow others to use your
 * version of this file under the LGPL, indicate your decision by
 * deletingthe provisions above and replace them with the notice and
 * other provisions required by the MPL or the GPL, as the case may be.
 * If you do not delete the provisions above, a recipient may use your
 * version of this file under any of the LGPL, the MPL or the GPL.
 */

/*
 * Lifetime-based fast allocation, inspired by much prior art, including
 * "Fast Allocation and Deallocation of Memory Based on Object Lifetimes"
 * David R. Hanson, Software -- Practice and Experience, Vol. 20(1).
 */
 
#include <config.h>
#include <stdlib.h>
#include <string.h>
#include <kglobal.h>
#include "arena.h"

#ifdef HAVE_GETPAGESIZE
#include <unistd.h>
#define POOL_SIZE kMax(8192u, 2*( unsigned ) getpagesize())
#else
#define POOL_SIZE 8192
#endif

//#define DEBUG_ARENA_MALLOC 
#ifdef DEBUG_ARENA_MALLOC
#include <assert.h>
#include <stdio.h>
#endif

namespace khtml {

#ifdef DEBUG_ARENA_MALLOC
static int i = 0;
#endif

#define FREELIST_MAX 50
#define LARGE_ALLOCATION_CEIL(pool) (pool)->arenasize * 256
#define MAX_DISCRETE_ALLOCATION(pool) (pool)->arenasize * 32
static Arena *arena_freelist = 0;
static int freelist_count = 0;

#define ARENA_DEFAULT_ALIGN  sizeof(double)
#define BIT(n)				 ((unsigned int)1 << (n))
#define BITMASK(n) 		  	 (BIT(n) - 1)
#define CEILING_LOG2(_log2,_n)   \
      unsigned int j_ = (unsigned int)(_n);   \
      (_log2) = 0;                    \
      if ((j_) & ((j_)-1))            \
      (_log2) += 1;               \
      if ((j_) >> 16)                 \
      (_log2) += 16, (j_) >>= 16; \
      if ((j_) >> 8)                  \
      (_log2) += 8, (j_) >>= 8;   \
      if ((j_) >> 4)                  \
      (_log2) += 4, (j_) >>= 4;   \
      if ((j_) >> 2)                  \
      (_log2) += 2, (j_) >>= 2;   \
      if ((j_) >> 1)                  \
      (_log2) += 1;

int CeilingLog2(unsigned int i) {
    int log2;
    CEILING_LOG2(log2,i);
    return log2;
}

void InitArenaPool(ArenaPool *pool, const char* /*name*/,
                   unsigned int /*size*/, unsigned int align)
{
     unsigned int size = POOL_SIZE;
     if (align == 0)
         align = ARENA_DEFAULT_ALIGN;
     pool->mask = BITMASK(CeilingLog2(align));
     pool->first.next = NULL;
     pool->first.base = pool->first.avail = pool->first.limit =
         (uword)ARENA_ALIGN(pool, &pool->first + 1);
     pool->current = &pool->first;
     pool->arenasize = size;
     pool->largealloc = LARGE_ALLOCATION_CEIL(pool);
     pool->cumul = 0;
}


/*
 ** ArenaAllocate() -- allocate space from an arena pool
 **
 ** Description: ArenaAllocate() allocates space from an arena
 ** pool.
 **
 ** First try to satisfy the request from arenas starting at
 ** pool->current.
 **
 ** If there is not enough space in the arena pool->current, try
 ** to claim an arena, on a first fit basis, from the global
 ** freelist (arena_freelist).
 **
 ** If no arena in arena_freelist is suitable, then try to
 ** allocate a new arena from the heap.
 **
 ** Returns: pointer to allocated space or NULL
 **
 */
void* ArenaAllocate(ArenaPool *pool, unsigned int nb)
{
    Arena *a;
    char *rp;     /* returned pointer */

#ifdef DEBUG_ARENA_MALLOC
    assert((nb & pool->mask) == 0);
#endif

    nb = (uword)ARENA_ALIGN(pool, nb); /* force alignment */

    /* attempt to allocate from arenas at pool->current */
    {
        a = pool->current;
        do {
            if ( a->avail +nb <= a->limit )  {
                pool->current = a;
                rp = (char *)a->avail;
                a->avail += nb;
                VALGRIND_MEMPOOL_ALLOC(a->base, rp, nb);
                return rp;
            }
        } while( NULL != (a = a->next) );
    }

    /* attempt to allocate from arena_freelist */
    {
        Arena *p; /* previous pointer, for unlinking from freelist */

        for ( a = p = arena_freelist; a != NULL ; p = a, a = a->next ) {
            if ( a->base +nb <= a->limit )  {
                if ( p == arena_freelist )
                    arena_freelist = a->next;
                else
                    p->next = a->next;
                a->avail = a->base;
                rp = (char *)a->avail;
                a->avail += nb;
                VALGRIND_MEMPOOL_ALLOC(a->base, rp, nb);
                /* the newly allocated arena is linked after pool->current
                 *  and becomes pool->current */
                a->next = pool->current->next;
                pool->current->next = a;
                pool->current = a;
                if ( 0 == pool->first.next )
                    pool->first.next = a;
                freelist_count--;
                return(rp);
            }
        }
    }

    /* attempt to allocate from the heap */
    {
        unsigned int sz;
#ifdef HAVE_MMAP
        if (pool->cumul > pool->largealloc) {
            // High memory pressure. Switch to a fractional allocation strategy
            // so that malloc gets a chance to successfully trim us down when it's over.
            sz = kMin(pool->cumul/25, MAX_DISCRETE_ALLOCATION(pool));
        } else
#endif
           sz = pool->arenasize > nb ? pool->arenasize : nb;
        sz += sizeof *a + pool->mask;  /* header and alignment slop */
        pool->cumul += sz;
#ifdef DEBUG_ARENA_MALLOC
        i++;
        printf("Malloc: %d\n", i);
#endif
        a = (Arena*)malloc(sz);
        if (a)  {
            a->limit = (uword)a + sz;
            a->base = a->avail = (uword)ARENA_ALIGN(pool, a + 1);
            VALGRIND_CREATE_MEMPOOL(a->base, 0, 0);
            rp = (char *)a->avail;
            a->avail += nb;
            VALGRIND_MEMPOOL_ALLOC(a->base, rp, nb);

            /* the newly allocated arena is linked after pool->current
            *  and becomes pool->current */
            a->next = pool->current->next;
            pool->current->next = a;
            pool->current = a;
            if ( !pool->first.next )
                pool->first.next = a;
            return(rp);
       }
    }

    /* we got to here, and there's no memory to allocate */
    return(0);
} /* --- end ArenaAllocate() --- */

/*
 * Free tail arenas linked after head, which may not be the true list head.
 * Reset pool->current to point to head in case it pointed at a tail arena.
 */
static void FreeArenaList(ArenaPool *pool, Arena *head, bool reallyFree)
{
    Arena **ap, *a;

    ap = &head->next;
    a = *ap;
    if (!a)
        return;

#ifdef DEBUG_ARENA_MALLOC
    do {
        assert(a->base <= a->avail && a->avail <= a->limit);
        a->avail = a->base;
        CLEAR_UNUSED(a);
    } while ((a = a->next) != 0);
    a = *ap;
#endif

    if (freelist_count >= FREELIST_MAX)
        reallyFree = true;

    if (reallyFree) {
        do {
            *ap = a->next;
            VALGRIND_DESTROY_MEMPOOL(a->base);
            CLEAR_ARENA(a);
#ifdef DEBUG_ARENA_MALLOC
            if (a) {
                i--;
                printf("Free: %d\n", i);
            }
#endif
            free(a); a = 0;
        } while ((a = *ap) != 0);
    } else {
        /* Insert as much of the arena chain as we can hold at the front of the freelist. */
        do {
            ap = &(*ap)->next;
            freelist_count++;
        } while (*ap && freelist_count < FREELIST_MAX);
        
        /* Get rid of excess */
        if (*ap) {
            Arena *xa, *n;
            for (xa = *ap; xa; xa = n) {
                VALGRIND_DESTROY_MEMPOOL(xa->base);
                n = xa->next;
#ifdef DEBUG_ARENA_MALLOC
                i--;
                printf("Free: %d\n", i);
#endif
                CLEAR_ARENA(xa);
                free(xa);
            }
        }                                    
        *ap = arena_freelist;
        arena_freelist = a;
        head->next = 0;
    }
    pool->current = head;
}

void ArenaRelease(ArenaPool *pool, char *mark)
{
    Arena *a;

    for (a = pool->first.next; a; a = a->next) {
        if (UPTRDIFF(mark, a->base) < UPTRDIFF(a->avail, a->base)) {
            a->avail = (uword)ARENA_ALIGN(pool, mark);
            FreeArenaList(pool, a, false);
            return;
        }
    }
}

void FreeArenaPool(ArenaPool *pool)
{
    FreeArenaList(pool, &pool->first, false);
}

void FinishArenaPool(ArenaPool *pool)
{
    FreeArenaList(pool, &pool->first, true);
}

void ArenaFinish()
{
    Arena *a, *next;
#ifdef DEBUG_ARENA_MALLOC
    printf("releasing global Arena freelist\n");
#endif
    for (a = arena_freelist; a; a = next) {
        next = a->next;
        free(a); a = 0;
    }
    freelist_count = 0;
    arena_freelist = NULL;
}

} // namespace