3 * GC descriptors describe object layout.
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
10 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
21 #ifdef HAVE_SEMAPHORE_H
22 #include <semaphore.h>
35 #include "mono/sgen/sgen-gc.h"
36 #include "mono/sgen/gc-internal-agnostic.h"
37 #include "mono/sgen/sgen-array-list.h"
39 #define MAX_USER_DESCRIPTORS 16
41 #define MAKE_ROOT_DESC(type,val) ((type) | ((val) << ROOT_DESC_TYPE_SHIFT))
42 #define ALIGN_TO(val,align) ((((guint64)val) + ((align) - 1)) & ~((align) - 1))
45 static SgenArrayList complex_descriptors = SGEN_ARRAY_LIST_INIT (NULL, NULL, NULL, INTERNAL_MEM_COMPLEX_DESCRIPTORS);
46 static SgenUserRootMarkFunc user_descriptors [MAX_USER_DESCRIPTORS];
47 static int user_descriptors_next = 0;
48 static SgenDescriptor all_ref_root_descrs [32];
50 #ifdef HEAVY_STATISTICS
51 static guint64 stat_scanned_count_per_descriptor [DESC_TYPE_MAX];
52 static guint64 stat_copied_count_per_descriptor [DESC_TYPE_MAX];
56 alloc_complex_descriptor (gsize *bitmap, int numbits)
59 volatile gpointer *slot;
62 SGEN_ASSERT (0, sizeof (gsize) == sizeof (mword), "We expect gsize and mword to have same size");
64 numbits = ALIGN_TO (numbits, GC_BITS_PER_WORD);
65 nwords = numbits / GC_BITS_PER_WORD + 1;
68 /* linear search, so we don't have duplicates with domain load/unload
69 * this should not be performance critical or we'd have bigger issues
70 * (the number and size of complex descriptors should be small).
72 SGEN_ARRAY_LIST_FOREACH_SLOT (&complex_descriptors, slot) {
73 gsize first_word = *(gsize*)slot;
74 if (first_word == 0) {
75 /* Unused slots should be 0 so we simply skip them */
77 } else if (first_word == nwords) {
79 for (j = 0; j < nwords - 1; ++j) {
80 if (((gsize*)slot) [j + 1] != bitmap [j]) {
90 /* Skip the bitmap words */
91 __index += (guint32)(first_word - 1);
92 __offset += (guint32)(first_word - 1);
93 } SGEN_ARRAY_LIST_END_FOREACH_SLOT;
95 res = sgen_array_list_alloc_block (&complex_descriptors, nwords);
97 SGEN_LOG (6, "Complex descriptor %d, size: %d (total desc memory: %d)", res, nwords, complex_descriptors.capacity);
98 descriptor = (gsize*)sgen_array_list_get_slot (&complex_descriptors, res);
99 descriptor [0] = nwords;
100 for (i = 0; i < nwords - 1; ++i) {
101 descriptor [1 + i] = bitmap [i];
102 SGEN_LOG (6, "\tvalue: %p", (void*)descriptor [1 + i]);
109 sgen_get_complex_descriptor (SgenDescriptor desc)
111 return (gsize*) sgen_array_list_get_slot (&complex_descriptors, desc >> LOW_TYPE_BITS);
115 * Descriptor builders.
118 mono_gc_make_descr_for_object (gsize *bitmap, int numbits, size_t obj_size)
120 int first_set = -1, num_set = 0, last_set = -1, i;
121 SgenDescriptor desc = 0;
122 size_t stored_size = SGEN_ALIGN_UP (obj_size);
124 for (i = 0; i < numbits; ++i) {
125 if (bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
134 SGEN_LOG (6, "Ptrfree descriptor %p, size: %zd", (void*)desc, stored_size);
135 if (stored_size <= MAX_RUNLEN_OBJECT_SIZE && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE)
136 return DESC_TYPE_SMALL_PTRFREE | stored_size;
137 return DESC_TYPE_COMPLEX_PTRFREE;
140 g_assert (!(stored_size & 0x7));
142 SGEN_ASSERT (5, stored_size == SGEN_ALIGN_UP (stored_size), "Size is not aligned");
144 /* we know the 2-word header is ptr-free */
145 if (last_set < BITMAP_NUM_BITS + OBJECT_HEADER_WORDS && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE) {
146 desc = DESC_TYPE_BITMAP | ((*bitmap >> OBJECT_HEADER_WORDS) << LOW_TYPE_BITS);
147 SGEN_LOG (6, "Largebitmap descriptor %p, size: %zd, last set: %d", (void*)desc, stored_size, last_set);
151 if (stored_size <= MAX_RUNLEN_OBJECT_SIZE && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE) {
152 /* check run-length encoding first: one byte offset, one byte number of pointers
153 * on 64 bit archs, we can have 3 runs, just one on 32.
154 * It may be better to use nibbles.
156 if (first_set < 256 && num_set < 256 && (first_set + num_set == last_set + 1)) {
157 desc = DESC_TYPE_RUN_LENGTH | stored_size | (first_set << 16) | (num_set << 24);
158 SGEN_LOG (6, "Runlen descriptor %p, size: %zd, first set: %d, num set: %d", (void*)desc, stored_size, first_set, num_set);
163 /* it's a complex object ... */
164 desc = DESC_TYPE_COMPLEX | (alloc_complex_descriptor (bitmap, last_set + 1) << LOW_TYPE_BITS);
168 /* If the array holds references, numbits == 1 and the first bit is set in elem_bitmap */
170 mono_gc_make_descr_for_array (int vector, gsize *elem_bitmap, int numbits, size_t elem_size)
172 int first_set = -1, num_set = 0, last_set = -1, i;
173 SgenDescriptor desc = DESC_TYPE_VECTOR | (vector ? VECTOR_KIND_SZARRAY : VECTOR_KIND_ARRAY);
174 for (i = 0; i < numbits; ++i) {
175 if (elem_bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
184 if (elem_size <= MAX_ELEMENT_SIZE)
185 return desc | VECTOR_SUBTYPE_PTRFREE | (elem_size << VECTOR_ELSIZE_SHIFT);
186 return DESC_TYPE_COMPLEX_PTRFREE;
189 if (elem_size <= MAX_ELEMENT_SIZE) {
190 desc |= elem_size << VECTOR_ELSIZE_SHIFT;
192 return desc | VECTOR_SUBTYPE_PTRFREE;
194 /* Note: we also handle structs with just ref fields */
195 if (num_set * sizeof (gpointer) == elem_size) {
196 return desc | VECTOR_SUBTYPE_REFS | ((gsize)(-1) << 16);
198 /* FIXME: try run-len first */
199 /* Note: we can't skip the object header here, because it's not present */
200 if (last_set < VECTOR_BITMAP_SIZE) {
201 return desc | VECTOR_SUBTYPE_BITMAP | (*elem_bitmap << 16);
204 /* it's am array of complex structs ... */
205 desc = DESC_TYPE_COMPLEX_ARR;
206 desc |= alloc_complex_descriptor (elem_bitmap, last_set + 1) << LOW_TYPE_BITS;
210 /* Return the bitmap encoded by a descriptor */
212 mono_gc_get_bitmap_for_descr (SgenDescriptor descr, int *numbits)
214 SgenDescriptor d = (SgenDescriptor)descr;
217 switch (d & DESC_TYPE_MASK) {
218 case DESC_TYPE_RUN_LENGTH: {
219 int first_set = (d >> 16) & 0xff;
220 int num_set = (d >> 24) & 0xff;
223 bitmap = g_new0 (gsize, (first_set + num_set + 7) / 8);
225 for (i = first_set; i < first_set + num_set; ++i)
226 bitmap [i / GC_BITS_PER_WORD] |= ((gsize)1 << (i % GC_BITS_PER_WORD));
228 *numbits = first_set + num_set;
233 case DESC_TYPE_BITMAP: {
234 gsize bmap = (d >> LOW_TYPE_BITS) << OBJECT_HEADER_WORDS;
236 bitmap = g_new0 (gsize, 1);
246 case DESC_TYPE_COMPLEX: {
247 gsize *bitmap_data = sgen_get_complex_descriptor (d);
248 int bwords = (int)(*bitmap_data) - 1;//Max scalar object size is 1Mb, which means up to 32k descriptor words
251 bitmap = g_new0 (gsize, bwords);
252 *numbits = bwords * GC_BITS_PER_WORD;
254 for (i = 0; i < bwords; ++i) {
255 bitmap [i] = bitmap_data [i + 1];
262 g_assert_not_reached ();
267 * mono_gc_make_descr_from_bitmap:
270 mono_gc_make_descr_from_bitmap (gsize *bitmap, int numbits)
273 return MAKE_ROOT_DESC (ROOT_DESC_BITMAP, 0);
274 } else if (numbits < ((sizeof (*bitmap) * 8) - ROOT_DESC_TYPE_SHIFT)) {
275 return MAKE_ROOT_DESC (ROOT_DESC_BITMAP, bitmap [0]);
277 SgenDescriptor complex = alloc_complex_descriptor (bitmap, numbits);
278 return MAKE_ROOT_DESC (ROOT_DESC_COMPLEX, complex);
283 mono_gc_make_vector_descr (void)
285 return MAKE_ROOT_DESC (ROOT_DESC_VECTOR, 0);
289 mono_gc_make_root_descr_all_refs (int numbits)
292 SgenDescriptor descr;
293 int num_bytes = numbits / 8;
295 if (numbits < 32 && all_ref_root_descrs [numbits])
296 return all_ref_root_descrs [numbits];
298 gc_bitmap = (gsize *)g_malloc0 (ALIGN_TO (ALIGN_TO (numbits, 8) + 1, sizeof (gsize)));
299 memset (gc_bitmap, 0xff, num_bytes);
300 if (numbits < ((sizeof (*gc_bitmap) * 8) - ROOT_DESC_TYPE_SHIFT))
301 gc_bitmap[0] = GUINT64_TO_LE(gc_bitmap[0]);
302 else if (numbits && num_bytes % (sizeof (*gc_bitmap)))
303 gc_bitmap[num_bytes / 8] = GUINT64_TO_LE(gc_bitmap [num_bytes / 8]);
305 gc_bitmap [numbits / 8] = (1 << (numbits % 8)) - 1;
306 descr = mono_gc_make_descr_from_bitmap (gc_bitmap, numbits);
310 all_ref_root_descrs [numbits] = descr;
316 sgen_make_user_root_descriptor (SgenUserRootMarkFunc marker)
318 SgenDescriptor descr;
320 g_assert (user_descriptors_next < MAX_USER_DESCRIPTORS);
321 descr = MAKE_ROOT_DESC (ROOT_DESC_USER, (SgenDescriptor)user_descriptors_next);
322 user_descriptors [user_descriptors_next ++] = marker;
328 sgen_get_complex_descriptor_bitmap (SgenDescriptor desc)
330 return (void*) sgen_array_list_get_slot (&complex_descriptors, desc >> ROOT_DESC_TYPE_SHIFT);
334 sgen_get_user_descriptor_func (SgenDescriptor desc)
336 return user_descriptors [desc >> ROOT_DESC_TYPE_SHIFT];
339 #ifdef HEAVY_STATISTICS
341 sgen_descriptor_count_scanned_object (SgenDescriptor desc)
343 int type = desc & DESC_TYPE_MASK;
344 SGEN_ASSERT (0, type, "Descriptor type can't be zero");
345 ++stat_scanned_count_per_descriptor [type - 1];
349 sgen_descriptor_count_copied_object (SgenDescriptor desc)
351 int type = desc & DESC_TYPE_MASK;
352 SGEN_ASSERT (0, type, "Descriptor type can't be zero");
353 ++stat_copied_count_per_descriptor [type - 1];
358 sgen_init_descriptors (void)
360 #ifdef HEAVY_STATISTICS
361 mono_counters_register ("# scanned RUN_LENGTH", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_RUN_LENGTH - 1]);
362 mono_counters_register ("# scanned SMALL_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_SMALL_PTRFREE - 1]);
363 mono_counters_register ("# scanned COMPLEX", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX - 1]);
364 mono_counters_register ("# scanned VECTOR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_VECTOR - 1]);
365 mono_counters_register ("# scanned BITMAP", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_BITMAP - 1]);
366 mono_counters_register ("# scanned COMPLEX_ARR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_ARR - 1]);
367 mono_counters_register ("# scanned COMPLEX_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_PTRFREE - 1]);
369 mono_counters_register ("# copied RUN_LENGTH", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_RUN_LENGTH - 1]);
370 mono_counters_register ("# copied SMALL_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_SMALL_PTRFREE - 1]);
371 mono_counters_register ("# copied COMPLEX", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX - 1]);
372 mono_counters_register ("# copied VECTOR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_VECTOR - 1]);
373 mono_counters_register ("# copied BITMAP", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_BITMAP - 1]);
374 mono_counters_register ("# copied COMPLEX_ARR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX_ARR - 1]);
375 mono_counters_register ("# copied COMPLEX_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX_PTRFREE - 1]);