summaryrefslogtreecommitdiff
path: root/allchblk.c
blob: ff94b4803ac0c6409ab0652095ef593f29834cdd (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
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
/* 
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
 * Copyright (c) 1998 by Silicon Graphics.  All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program
 * for any purpose,  provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 */
/* Boehm, August 9, 1995 5:08 pm PDT */

#define DEBUG
#undef DEBUG
#include <stdio.h>
#include "gc_priv.h"


/*
 * allocate/free routines for heap blocks
 * Note that everything called from outside the garbage collector
 * should be prepared to abort at any point as the result of a signal.
 */

/*
 * Free heap blocks are kept on a list sorted by address.
 * The hb_hdr.hbh_sz field of a free heap block contains the length
 * (in bytes) of the entire block.
 * Neighbors are coalesced.
 */
 
# define MAX_BLACK_LIST_ALLOC (2*HBLKSIZE)
		/* largest block we will allocate starting on a black   */
		/* listed block.  Must be >= HBLKSIZE.			*/

struct hblk * GC_hblkfreelist = 0;

struct hblk *GC_savhbp = (struct hblk *)0;  /* heap block preceding next */
					 /* block to be examined by   */
					 /* GC_allochblk.                */

# if !defined(NO_DEBUGGING)
void GC_print_hblkfreelist()
{
    struct hblk * h = GC_hblkfreelist;
    word total_free = 0;
    hdr * hhdr = HDR(h);
    word sz;
    
    while (h != 0) {
        sz = hhdr -> hb_sz;
    	GC_printf2("0x%lx size %lu ", (unsigned long)h, (unsigned long)sz);
    	total_free += sz;
        if (GC_is_black_listed(h, HBLKSIZE) != 0) {
             GC_printf0("start black listed\n");
        } else if (GC_is_black_listed(h, hhdr -> hb_sz) != 0) {
             GC_printf0("partially black listed\n");
        } else {
             GC_printf0("not black listed\n");
        }
        h = hhdr -> hb_next;
        hhdr = HDR(h);
    }
    GC_printf1("Total of %lu bytes on free list\n", (unsigned long)total_free);
}

# endif /* NO_DEBUGGING */

/* Initialize hdr for a block containing the indicated size and 	*/
/* kind of objects.							*/
/* Return FALSE on failure.						*/
static GC_bool setup_header(hhdr, sz, kind, flags)
register hdr * hhdr;
word sz;	/* object size in words */
int kind;
unsigned char flags;
{
    register word descr;
    
    /* Add description of valid object pointers */
      if (!GC_add_map_entry(sz)) return(FALSE);
      hhdr -> hb_map = GC_obj_map[sz > MAXOBJSZ? 0 : sz];
      
    /* Set size, kind and mark proc fields */
      hhdr -> hb_sz = sz;
      hhdr -> hb_obj_kind = kind;
      hhdr -> hb_flags = flags;
      descr = GC_obj_kinds[kind].ok_descriptor;
      if (GC_obj_kinds[kind].ok_relocate_descr) descr += WORDS_TO_BYTES(sz);
      hhdr -> hb_descr = descr;
      
    /* Clear mark bits */
      GC_clear_hdr_marks(hhdr);
      
    hhdr -> hb_last_reclaimed = (unsigned short)GC_gc_no;
    return(TRUE);
}

#ifdef EXACT_FIRST
#   define LAST_TRIP 2
#else
#   define LAST_TRIP 1
#endif

word GC_max_hblk_size = HBLKSIZE;
	
/*
 * Allocate (and return pointer to) a heap block
 *   for objects of size sz words.
 *
 * NOTE: We set obj_map field in header correctly.
 *       Caller is resposnsible for building an object freelist in block.
 *
 * We clear the block if it is destined for large objects, and if
 * kind requires that newly allocated objects be cleared.
 */
struct hblk *
GC_allochblk(sz, kind, flags)
word sz;
int kind;
unsigned char flags;  /* IGNORE_OFF_PAGE or 0 */
{
    register struct hblk *thishbp;
    register hdr * thishdr;		/* Header corr. to thishbp */
    register struct hblk *hbp;
    register hdr * hhdr;		/* Header corr. to hbp */
    struct hblk *prevhbp;
    register hdr * phdr;		/* Header corr. to prevhbp */
    signed_word size_needed;    /* number of bytes in requested objects */
    signed_word size_avail;	/* bytes available in this block	*/
    int trip_count = 0;

    size_needed = HBLKSIZE * OBJ_SZ_TO_BLOCKS(sz);
    if ((word)size_needed >  GC_max_hblk_size)
	GC_max_hblk_size = size_needed;

    /* search for a big enough block in free list */
	hbp = GC_savhbp;
	hhdr = HDR(hbp);
	for(;;) {

	    prevhbp = hbp;
	    phdr = hhdr;
	    hbp = (prevhbp == 0? GC_hblkfreelist : phdr->hb_next);
	    hhdr = HDR(hbp);

	    if( prevhbp == GC_savhbp) {
		if (trip_count == LAST_TRIP) return(0);
		++trip_count;
	    }

	    if( hbp == 0 ) continue;

	    size_avail = hhdr->hb_sz;
#	    ifdef EXACT_FIRST
		if (trip_count <= 1 && size_avail != size_needed) continue;
#	    endif
	    if (size_avail < size_needed) continue;
#	    ifdef PRESERVE_LAST
		if (size_avail != size_needed
		    && !GC_incremental
		    && (word)size_needed <= GC_max_hblk_size/2
		    && GC_in_last_heap_sect((ptr_t)hbp)
		    && GC_should_collect()) {
		    continue;
		} 
#	    endif
	    /* If the next heap block is obviously better, go on.	*/
	    /* This prevents us from disassembling a single large block */
	    /* to get tiny blocks.					*/
	    {
	      signed_word next_size;
	      
	      thishbp = hhdr -> hb_next;
	      if (thishbp == 0) thishbp = GC_hblkfreelist; 
	      thishdr = HDR(thishbp);
	      next_size = (signed_word)(thishdr -> hb_sz);
	      if (next_size < size_avail
	          && next_size >= size_needed
	          && !GC_is_black_listed(thishbp, (word)size_needed)) {
	          continue;
	      }
	    }
	    if ( !IS_UNCOLLECTABLE(kind) &&
	         (kind != PTRFREE || size_needed > MAX_BLACK_LIST_ALLOC)) {
	      struct hblk * lasthbp = hbp;
	      ptr_t search_end = (ptr_t)hbp + size_avail - size_needed;
	      signed_word orig_avail = size_avail;
	      signed_word eff_size_needed = ((flags & IGNORE_OFF_PAGE)?
	      					HBLKSIZE
	      					: size_needed);
	      
	      
	      while ((ptr_t)lasthbp <= search_end
	             && (thishbp = GC_is_black_listed(lasthbp,
	             				      (word)eff_size_needed))) {
	        lasthbp = thishbp;
	      }
	      size_avail -= (ptr_t)lasthbp - (ptr_t)hbp;
	      thishbp = lasthbp;
	      if (size_avail >= size_needed) {
	        if (thishbp != hbp && GC_install_header(thishbp)) {
	          /* Split the block at thishbp */
	              thishdr = HDR(thishbp);
	              /* GC_invalidate_map not needed, since we will	*/
	              /* allocate this block.				*/
		      thishdr -> hb_next = hhdr -> hb_next;
		      thishdr -> hb_sz = size_avail;
		      hhdr -> hb_sz = (ptr_t)thishbp - (ptr_t)hbp;
		      hhdr -> hb_next = thishbp;
		  /* Advance to thishbp */
		      prevhbp = hbp;
		      phdr = hhdr;
		      hbp = thishbp;
		      hhdr = thishdr;
		}
	      } else if (size_needed > (signed_word)BL_LIMIT
	                 && orig_avail - size_needed
			    > (signed_word)BL_LIMIT) {
	        /* Punt, since anything else risks unreasonable heap growth. */
	        WARN("Needed to allocate blacklisted block at 0x%lx\n",
		     (word)hbp);
	        thishbp = hbp;
	        size_avail = orig_avail;
	      } else if (size_avail == 0
	      		 && size_needed == HBLKSIZE
	      		 && prevhbp != 0) {
#		ifndef FIND_LEAK
	      	  static unsigned count = 0;
	      	  
	      	  /* The block is completely blacklisted.  We need 	*/
	      	  /* to drop some such blocks, since otherwise we spend */
	      	  /* all our time traversing them if pointerfree	*/
	      	  /* blocks are unpopular.				*/
	          /* A dropped block will be reconsidered at next GC.	*/
	          if ((++count & 3) == 0) {
	            /* Allocate and drop the block in small chunks, to	*/
	            /* maximize the chance that we will recover some	*/
	            /* later.						*/
	              struct hblk * limit = hbp + (hhdr->hb_sz/HBLKSIZE);
	              struct hblk * h;
	              
		      GC_words_wasted += hhdr->hb_sz;
	              phdr -> hb_next = hhdr -> hb_next;
	              for (h = hbp; h < limit; h++) {
	                if (h == hbp || GC_install_header(h)) {
	                  hhdr = HDR(h);
	                  (void) setup_header(
	                	  hhdr,
	              		  BYTES_TO_WORDS(HBLKSIZE - HDR_BYTES),
	              		  PTRFREE, 0); /* Cant fail */
	              	  if (GC_debugging_started) {
	              	    BZERO(hbp + HDR_BYTES, HBLKSIZE - HDR_BYTES);
	              	  }
	                }
	              }
	            /* Restore hbp to point at free block */
	              if (GC_savhbp == hbp) GC_savhbp = prevhbp;
	              hbp = prevhbp;
	              hhdr = phdr;
	              if (hbp == GC_savhbp) --trip_count;
	          }
#		endif
	      }
	    }
	    if( size_avail >= size_needed ) {
		/* found a big enough block       */
		/* let thishbp --> the block      */
		/* set prevhbp, hbp to bracket it */
		    thishbp = hbp;
		    thishdr = hhdr;
		    if( size_avail == size_needed ) {
			hbp = hhdr->hb_next;
			hhdr = HDR(hbp);
		    } else {
			hbp = (struct hblk *)
			    (((word)thishbp) + size_needed);
			if (!GC_install_header(hbp)) {
			    hbp = thishbp;
			    continue;
			}
			hhdr = HDR(hbp);
			GC_invalidate_map(hhdr);
			hhdr->hb_next = thishdr->hb_next;
			hhdr->hb_sz = size_avail - size_needed;
		    }
		/* remove *thishbp from hblk freelist */
		    if( prevhbp == 0 ) {
			GC_hblkfreelist = hbp;
		    } else {
			phdr->hb_next = hbp;
		    }
		/* save current list search position */
		    GC_savhbp = hbp;
		break;
	    }
	}
	
    /* Notify virtual dirty bit implementation that we are about to write. */
    	GC_write_hint(thishbp);
	/* This should deal better with large blocks.	*/
    
    /* Add it to map of valid blocks */
    	if (!GC_install_counts(thishbp, (word)size_needed)) return(0);
    	/* This leaks memory under very rare conditions. */
    		
    /* Set up header */
        if (!setup_header(thishdr, sz, kind, flags)) {
            GC_remove_counts(thishbp, (word)size_needed);
            return(0); /* ditto */
        }
        
    /* Clear block if necessary */
	if (GC_debugging_started
	    || sz > MAXOBJSZ && GC_obj_kinds[kind].ok_init) {
	    BZERO(thishbp + HDR_BYTES,  size_needed - HDR_BYTES);
	}

    /* We just successfully allocated a block.  Restart count of	*/
    /* consecutive failures.						*/
    {
	extern unsigned GC_fail_count;
	
	GC_fail_count = 0;
    }
    
    return( thishbp );
}
 
struct hblk * GC_freehblk_ptr = 0;  /* Search position hint for GC_freehblk */

/*
 * Free a heap block.
 *
 * Coalesce the block with its neighbors if possible.
 *
 * All mark words are assumed to be cleared.
 */
void
GC_freehblk(p)
register struct hblk *p;
{
register hdr *phdr;	/* Header corresponding to p */
register struct hblk *hbp, *prevhbp;
register hdr *hhdr, *prevhdr;
register signed_word size;

    /* GC_savhbp may become invalid due to coalescing.  Clear it. */
	GC_savhbp = (struct hblk *)0;

    phdr = HDR(p);
    size = phdr->hb_sz;
    size = HBLKSIZE * OBJ_SZ_TO_BLOCKS(size);
    GC_remove_counts(p, (word)size);
    phdr->hb_sz = size;
    GC_invalidate_map(phdr);
    prevhbp = 0;
    
    /* The following optimization was suggested by David Detlefs.	*/
    /* Note that the header cannot be NIL, since there cannot be an	*/
    /* intervening  call to GC_freehblk without resetting		*/
    /* GC_freehblk_ptr.							*/
    if (GC_freehblk_ptr != 0 &&
    	HDR(GC_freehblk_ptr)->hb_map == GC_invalid_map &&
    	(ptr_t)GC_freehblk_ptr < (ptr_t)p) {
      hbp = GC_freehblk_ptr;
    } else {
      hbp = GC_hblkfreelist;
    };
    hhdr = HDR(hbp);

    while( (hbp != 0) && (hbp < p) ) {
	prevhbp = hbp;
	prevhdr = hhdr;
	hbp = hhdr->hb_next;
	hhdr = HDR(hbp);
    }
    GC_freehblk_ptr = prevhbp;
    
    /* Check for duplicate deallocation in the easy case */
      if (hbp != 0 && (ptr_t)p + size > (ptr_t)hbp
        || prevhbp != 0 && (ptr_t)prevhbp + prevhdr->hb_sz > (ptr_t)p) {
        GC_printf1("Duplicate large block deallocation of 0x%lx\n",
        	   (unsigned long) p);
        GC_printf2("Surrounding free blocks are 0x%lx and 0x%lx\n",
           	   (unsigned long) prevhbp, (unsigned long) hbp);
      }

    /* Coalesce with successor, if possible */
      if( (((word)p)+size) == ((word)hbp) ) {
	phdr->hb_next = hhdr->hb_next;
	phdr->hb_sz += hhdr->hb_sz;
	GC_remove_header(hbp);
      } else {
	phdr->hb_next = hbp;
      }

    
    if( prevhbp == 0 ) {
	GC_hblkfreelist = p;
    } else if( (((word)prevhbp) + prevhdr->hb_sz)
      	       == ((word)p) ) {
      /* Coalesce with predecessor */
	prevhdr->hb_next = phdr->hb_next;
	prevhdr->hb_sz += phdr->hb_sz;
	GC_remove_header(p);
    } else {
	prevhdr->hb_next = p;
    }
}