mono/sgen/sgen-descriptor.c

   1 /**
   2  * \file
   3  * GC descriptors describe object layout.
   4  *
   5  * Copyright 2001-2003 Ximian, Inc
   6  * Copyright 2003-2010 Novell, Inc.
   7  * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
   8  * Copyright (C) 2012 Xamarin Inc
   9  *
  10  * Licensed under the MIT license. See LICENSE file in the project root for full license information.
  11  */
  12 #include "config.h"
  13 #ifdef HAVE_SGEN_GC
  14
  15 #ifdef HAVE_UNISTD_H
  16 #include <unistd.h>
  17 #endif
  18 #ifdef HAVE_PTHREAD_H
  19 #include <pthread.h>
  20 #endif
  21 #ifdef HAVE_SEMAPHORE_H
  22 #include <semaphore.h>
  23 #endif
  24 #include <stdio.h>
  25 #include <string.h>
  26 #include <errno.h>
  27 #include <assert.h>
  28 #ifdef __MACH__
  29 #undef _XOPEN_SOURCE
  30 #endif
  31 #ifdef __MACH__
  32 #define _XOPEN_SOURCE
  33 #endif
  34
  35 #include "mono/sgen/sgen-gc.h"
  36 #include "mono/sgen/gc-internal-agnostic.h"
  37 #include "mono/sgen/sgen-array-list.h"
  38
  39 #define MAX_USER_DESCRIPTORS 16
  40
  41 #define MAKE_ROOT_DESC(type,val) ((type) | ((val) << ROOT_DESC_TYPE_SHIFT))
  42
  43 static SgenArrayList complex_descriptors = SGEN_ARRAY_LIST_INIT (NULL, NULL, NULL, INTERNAL_MEM_COMPLEX_DESCRIPTORS);
  44 static SgenUserRootMarkFunc user_descriptors [MAX_USER_DESCRIPTORS];
  45 static int user_descriptors_next = 0;
  46 static SgenDescriptor all_ref_root_descrs [32];
  47
  48 #ifdef HEAVY_STATISTICS
  49 static guint64 stat_scanned_count_per_descriptor [DESC_TYPE_MAX];
  50 static guint64 stat_copied_count_per_descriptor [DESC_TYPE_MAX];
  51 #endif
  52
  53 static int
  54 alloc_complex_descriptor (gsize *bitmap, int numbits)
  55 {
  56         int nwords, res, i;
  57         volatile gpointer *slot;
  58         gsize *descriptor;
  59
  60         SGEN_ASSERT (0, sizeof (gsize) == sizeof (mword), "We expect gsize and mword to have same size");
  61
  62         numbits = ALIGN_TO (numbits, GC_BITS_PER_WORD);
  63         nwords = numbits / GC_BITS_PER_WORD + 1;
  64
  65         sgen_gc_lock ();
  66         /* linear search, so we don't have duplicates with domain load/unload
  67          * this should not be performance critical or we'd have bigger issues
  68          * (the number and size of complex descriptors should be small).
  69          */
  70         SGEN_ARRAY_LIST_FOREACH_SLOT (&complex_descriptors, slot) {
  71                 gsize first_word = *(gsize*)slot;
  72                 if (first_word == 0) {
  73                         /* Unused slots should be 0 so we simply skip them */
  74                         continue;
  75                 } else if (first_word == nwords) {
  76                         int j, found = TRUE;
  77                         for (j = 0; j < nwords - 1; ++j) {
  78                                 if (((gsize*)slot) [j + 1] != bitmap [j]) {
  79                                         found = FALSE;
  80                                         break;
  81                                 }
  82                         }
  83                         if (found) {
  84                                 sgen_gc_unlock ();
  85                                 return __index;
  86                         }
  87                 }
  88                 /* Skip the bitmap words */
  89                 __index += (guint32)(first_word - 1);
  90                 __offset += (guint32)(first_word - 1);
  91         } SGEN_ARRAY_LIST_END_FOREACH_SLOT;
  92
  93         res = sgen_array_list_alloc_block (&complex_descriptors, nwords);
  94
  95         SGEN_LOG (6, "Complex descriptor %d, size: %d (total desc memory: %d)", res, nwords, complex_descriptors.capacity);
  96         descriptor = (gsize*)sgen_array_list_get_slot (&complex_descriptors, res);
  97         descriptor [0] = nwords;
  98         for (i = 0; i < nwords - 1; ++i) {
  99                 descriptor [1 + i] = bitmap [i];
 100                 SGEN_LOG (6, "\tvalue: %p", (void*)descriptor [1 + i]);
 101         }
 102         sgen_gc_unlock ();
 103         return res;
 104 }
 105
 106 gsize*
 107 sgen_get_complex_descriptor (SgenDescriptor desc)
 108 {
 109         return (gsize*) sgen_array_list_get_slot (&complex_descriptors, desc >> LOW_TYPE_BITS);
 110 }
 111
 112 /*
 113  * Descriptor builders.
 114  */
 115 SgenDescriptor
 116 mono_gc_make_descr_for_object (gsize *bitmap, int numbits, size_t obj_size)
 117 {
 118         int first_set = -1, num_set = 0, last_set = -1, i;
 119         SgenDescriptor desc = 0;
 120         size_t stored_size = SGEN_ALIGN_UP (obj_size);
 121
 122         for (i = 0; i < numbits; ++i) {
 123                 if (bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
 124                         if (first_set < 0)
 125                                 first_set = i;
 126                         last_set = i;
 127                         num_set++;
 128                 }
 129         }
 130
 131         if (first_set < 0) {
 132                 SGEN_LOG (6, "Ptrfree descriptor %p, size: %ld", (void*)desc, (long)stored_size);
 133                 if (stored_size <= MAX_RUNLEN_OBJECT_SIZE && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE)
 134                         return DESC_TYPE_SMALL_PTRFREE | stored_size;
 135                 return DESC_TYPE_COMPLEX_PTRFREE;
 136         }
 137
 138         g_assert (!(stored_size & 0x7));
 139
 140         SGEN_ASSERT (5, stored_size == SGEN_ALIGN_UP (stored_size), "Size is not aligned");
 141
 142         /* we know the 2-word header is ptr-free */
 143         if (last_set < BITMAP_NUM_BITS + OBJECT_HEADER_WORDS && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE) {
 144                 desc = DESC_TYPE_BITMAP | ((*bitmap >> OBJECT_HEADER_WORDS) << LOW_TYPE_BITS);
 145                 SGEN_LOG (6, "Largebitmap descriptor %p, size: %ld, last set: %d", (void*)desc, (long)stored_size, last_set);
 146                 return desc;
 147         }
 148
 149         if (stored_size <= MAX_RUNLEN_OBJECT_SIZE && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE) {
 150                 /* check run-length encoding first: one byte offset, one byte number of pointers
 151                  * on 64 bit archs, we can have 3 runs, just one on 32.
 152                  * It may be better to use nibbles.
 153                  */
 154                 if (first_set < 256 && num_set < 256 && (first_set + num_set == last_set + 1)) {
 155                         desc = DESC_TYPE_RUN_LENGTH | stored_size | (first_set << 16) | (num_set << 24);
 156                         SGEN_LOG (6, "Runlen descriptor %p, size: %ld, first set: %d, num set: %d", (void*)desc, (long)stored_size, first_set, num_set);
 157                         return desc;
 158                 }
 159         }
 160
 161         /* it's a complex object ... */
 162         desc = DESC_TYPE_COMPLEX | (alloc_complex_descriptor (bitmap, last_set + 1) << LOW_TYPE_BITS);
 163         return desc;
 164 }
 165
 166 /* If the array holds references, numbits == 1 and the first bit is set in elem_bitmap */
 167 SgenDescriptor
 168 mono_gc_make_descr_for_array (int vector, gsize *elem_bitmap, int numbits, size_t elem_size)
 169 {
 170         int first_set = -1, num_set = 0, last_set = -1, i;
 171         SgenDescriptor desc = DESC_TYPE_VECTOR | (vector ? VECTOR_KIND_SZARRAY : VECTOR_KIND_ARRAY);
 172         for (i = 0; i < numbits; ++i) {
 173                 if (elem_bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
 174                         if (first_set < 0)
 175                                 first_set = i;
 176                         last_set = i;
 177                         num_set++;
 178                 }
 179         }
 180
 181         if (first_set < 0) {
 182                 if (elem_size <= MAX_ELEMENT_SIZE)
 183                         return desc | VECTOR_SUBTYPE_PTRFREE | (elem_size << VECTOR_ELSIZE_SHIFT);
 184                 return DESC_TYPE_COMPLEX_PTRFREE;
 185         }
 186
 187         if (elem_size <= MAX_ELEMENT_SIZE) {
 188                 desc |= elem_size << VECTOR_ELSIZE_SHIFT;
 189                 if (!num_set) {
 190                         return desc | VECTOR_SUBTYPE_PTRFREE;
 191                 }
 192                 /* Note: we also handle structs with just ref fields */
 193                 if (num_set * sizeof (gpointer) == elem_size) {
 194                         return desc | VECTOR_SUBTYPE_REFS | ((gsize)(-1) << 16);
 195                 }
 196                 /* FIXME: try run-len first */
 197                 /* Note: we can't skip the object header here, because it's not present */
 198                 if (last_set < VECTOR_BITMAP_SIZE) {
 199                         return desc | VECTOR_SUBTYPE_BITMAP | (*elem_bitmap << 16);
 200                 }
 201         }
 202         /* it's am array of complex structs ... */
 203         desc = DESC_TYPE_COMPLEX_ARR;
 204         desc |= alloc_complex_descriptor (elem_bitmap, last_set + 1) << LOW_TYPE_BITS;
 205         return desc;
 206 }
 207
 208 /* Return the bitmap encoded by a descriptor */
 209 gsize*
 210 mono_gc_get_bitmap_for_descr (SgenDescriptor descr, int *numbits)
 211 {
 212         SgenDescriptor d = (SgenDescriptor)descr;
 213         gsize *bitmap;
 214
 215         switch (d & DESC_TYPE_MASK) {
 216         case DESC_TYPE_RUN_LENGTH: {
 217                 int first_set = (d >> 16) & 0xff;
 218                 int num_set = (d >> 24) & 0xff;
 219                 int i;
 220
 221                 bitmap = g_new0 (gsize, (first_set + num_set + 7) / 8);
 222
 223                 for (i = first_set; i < first_set + num_set; ++i)
 224                         bitmap [i / GC_BITS_PER_WORD] |= ((gsize)1 << (i % GC_BITS_PER_WORD));
 225
 226                 *numbits = first_set + num_set;
 227
 228                 return bitmap;
 229         }
 230
 231         case DESC_TYPE_BITMAP: {
 232                 gsize bmap = (d >> LOW_TYPE_BITS) << OBJECT_HEADER_WORDS;
 233
 234                 bitmap = g_new0 (gsize, 1);
 235                 bitmap [0] = bmap;
 236                 *numbits = 0;
 237                 while (bmap) {
 238                         (*numbits) ++;
 239                         bmap >>= 1;
 240                 }
 241                 return bitmap;
 242         }
 243
 244         case DESC_TYPE_COMPLEX: {
 245                 gsize *bitmap_data = sgen_get_complex_descriptor (d);
 246                 int bwords = (int)(*bitmap_data) - 1;//Max scalar object size is 1Mb, which means up to 32k descriptor words
 247                 int i;
 248
 249                 bitmap = g_new0 (gsize, bwords);
 250                 *numbits = bwords * GC_BITS_PER_WORD;
 251
 252                 for (i = 0; i < bwords; ++i) {
 253                         bitmap [i] = bitmap_data [i + 1];
 254                 }
 255
 256                 return bitmap;
 257         }
 258
 259         default:
 260                 g_assert_not_reached ();
 261         }
 262 }
 263
 264 /**
 265  * mono_gc_make_descr_from_bitmap:
 266  */
 267 SgenDescriptor
 268 mono_gc_make_descr_from_bitmap (gsize *bitmap, int numbits)
 269 {
 270         if (numbits == 0) {
 271                 return MAKE_ROOT_DESC (ROOT_DESC_BITMAP, 0);
 272         } else if (numbits < ((sizeof (*bitmap) * 8) - ROOT_DESC_TYPE_SHIFT)) {
 273                 return MAKE_ROOT_DESC (ROOT_DESC_BITMAP, bitmap [0]);
 274         } else {
 275                 SgenDescriptor complex = alloc_complex_descriptor (bitmap, numbits);
 276                 return MAKE_ROOT_DESC (ROOT_DESC_COMPLEX, complex);
 277         }
 278 }
 279
 280 SgenDescriptor
 281 mono_gc_make_vector_descr (void)
 282 {
 283         return MAKE_ROOT_DESC (ROOT_DESC_VECTOR, 0);
 284 }
 285
 286 SgenDescriptor
 287 mono_gc_make_root_descr_all_refs (int numbits)
 288 {
 289         gsize *gc_bitmap;
 290         SgenDescriptor descr;
 291         int num_bytes = numbits / 8;
 292
 293         if (numbits < 32 && all_ref_root_descrs [numbits])
 294                 return all_ref_root_descrs [numbits];
 295
 296         gc_bitmap = (gsize *)g_malloc0 (ALIGN_TO (ALIGN_TO (numbits, 8) + 1, sizeof (gsize)));
 297         memset (gc_bitmap, 0xff, num_bytes);
 298         if (numbits < ((sizeof (*gc_bitmap) * 8) - ROOT_DESC_TYPE_SHIFT))
 299                 gc_bitmap[0] = GUINT64_TO_LE(gc_bitmap[0]);
 300         else if (numbits && num_bytes % (sizeof (*gc_bitmap)))
 301                 gc_bitmap[num_bytes / 8] = GUINT64_TO_LE(gc_bitmap [num_bytes / 8]);
 302         if (numbits % 8)
 303                 gc_bitmap [numbits / 8] = (1 << (numbits % 8)) - 1;
 304         descr = mono_gc_make_descr_from_bitmap (gc_bitmap, numbits);
 305         g_free (gc_bitmap);
 306
 307         if (numbits < 32)
 308                 all_ref_root_descrs [numbits] = descr;
 309
 310         return descr;
 311 }
 312
 313 SgenDescriptor
 314 sgen_make_user_root_descriptor (SgenUserRootMarkFunc marker)
 315 {
 316         SgenDescriptor descr;
 317
 318         g_assert (user_descriptors_next < MAX_USER_DESCRIPTORS);
 319         descr = MAKE_ROOT_DESC (ROOT_DESC_USER, (SgenDescriptor)user_descriptors_next);
 320         user_descriptors [user_descriptors_next ++] = marker;
 321
 322         return descr;
 323 }
 324
 325 void*
 326 sgen_get_complex_descriptor_bitmap (SgenDescriptor desc)
 327 {
 328         return (void*) sgen_array_list_get_slot (&complex_descriptors, desc >> ROOT_DESC_TYPE_SHIFT);
 329 }
 330
 331 SgenUserRootMarkFunc
 332 sgen_get_user_descriptor_func (SgenDescriptor desc)
 333 {
 334         return user_descriptors [desc >> ROOT_DESC_TYPE_SHIFT];
 335 }
 336
 337 #ifdef HEAVY_STATISTICS
 338 void
 339 sgen_descriptor_count_scanned_object (SgenDescriptor desc)
 340 {
 341         int type = desc & DESC_TYPE_MASK;
 342         SGEN_ASSERT (0, type, "Descriptor type can't be zero");
 343         ++stat_scanned_count_per_descriptor [type - 1];
 344 }
 345
 346 void
 347 sgen_descriptor_count_copied_object (SgenDescriptor desc)
 348 {
 349         int type = desc & DESC_TYPE_MASK;
 350         SGEN_ASSERT (0, type, "Descriptor type can't be zero");
 351         ++stat_copied_count_per_descriptor [type - 1];
 352 }
 353 #endif
 354
 355 void
 356 sgen_init_descriptors (void)
 357 {
 358 #ifdef HEAVY_STATISTICS
 359         mono_counters_register ("# scanned RUN_LENGTH", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_RUN_LENGTH - 1]);
 360         mono_counters_register ("# scanned SMALL_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_SMALL_PTRFREE - 1]);
 361         mono_counters_register ("# scanned COMPLEX", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX - 1]);
 362         mono_counters_register ("# scanned VECTOR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_VECTOR - 1]);
 363         mono_counters_register ("# scanned BITMAP", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_BITMAP - 1]);
 364         mono_counters_register ("# scanned COMPLEX_ARR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_ARR - 1]);
 365         mono_counters_register ("# scanned COMPLEX_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_PTRFREE - 1]);
 366
 367         mono_counters_register ("# copied RUN_LENGTH", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_RUN_LENGTH - 1]);
 368         mono_counters_register ("# copied SMALL_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_SMALL_PTRFREE - 1]);
 369         mono_counters_register ("# copied COMPLEX", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX - 1]);
 370         mono_counters_register ("# copied VECTOR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_VECTOR - 1]);
 371         mono_counters_register ("# copied BITMAP", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_BITMAP - 1]);
 372         mono_counters_register ("# copied COMPLEX_ARR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX_ARR - 1]);
 373         mono_counters_register ("# copied COMPLEX_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX_PTRFREE - 1]);
 374 #endif
 375 }
 376
 377 #endif