2 * sgen-descriptor.c: GC descriptors describe object layout.
4 * Copyright 2001-2003 Ximian, Inc
5 * Copyright 2003-2010 Novell, Inc.
6 * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
7 * Copyright (C) 2012 Xamarin Inc
9 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
20 #ifdef HAVE_SEMAPHORE_H
21 #include <semaphore.h>
34 #include "mono/sgen/sgen-gc.h"
35 #include "mono/sgen/gc-internal-agnostic.h"
36 #include "mono/sgen/sgen-array-list.h"
38 #define MAX_USER_DESCRIPTORS 16
40 #define MAKE_ROOT_DESC(type,val) ((type) | ((val) << ROOT_DESC_TYPE_SHIFT))
41 #define ALIGN_TO(val,align) ((((guint64)val) + ((align) - 1)) & ~((align) - 1))
44 static SgenArrayList complex_descriptors = SGEN_ARRAY_LIST_INIT (NULL, NULL, NULL, INTERNAL_MEM_COMPLEX_DESCRIPTORS);
45 static SgenUserRootMarkFunc user_descriptors [MAX_USER_DESCRIPTORS];
46 static int user_descriptors_next = 0;
47 static SgenDescriptor all_ref_root_descrs [32];
49 #ifdef HEAVY_STATISTICS
50 static guint64 stat_scanned_count_per_descriptor [DESC_TYPE_MAX];
51 static guint64 stat_copied_count_per_descriptor [DESC_TYPE_MAX];
55 alloc_complex_descriptor (gsize *bitmap, int numbits)
58 volatile gpointer *slot;
61 SGEN_ASSERT (0, sizeof (gsize) == sizeof (mword), "We expect gsize and mword to have same size");
63 numbits = ALIGN_TO (numbits, GC_BITS_PER_WORD);
64 nwords = numbits / GC_BITS_PER_WORD + 1;
67 /* linear search, so we don't have duplicates with domain load/unload
68 * this should not be performance critical or we'd have bigger issues
69 * (the number and size of complex descriptors should be small).
71 SGEN_ARRAY_LIST_FOREACH_SLOT (&complex_descriptors, slot) {
72 gsize first_word = *(gsize*)slot;
73 if (first_word == 0) {
74 /* Unused slots should be 0 so we simply skip them */
76 } else if (first_word == nwords) {
78 for (j = 0; j < nwords - 1; ++j) {
79 if (((gsize*)slot) [j + 1] != bitmap [j]) {
89 /* Skip the bitmap words */
90 __index += (guint32)(first_word - 1);
91 __offset += (guint32)(first_word - 1);
92 } SGEN_ARRAY_LIST_END_FOREACH_SLOT;
94 res = sgen_array_list_alloc_block (&complex_descriptors, nwords);
96 SGEN_LOG (6, "Complex descriptor %d, size: %d (total desc memory: %d)", res, nwords, complex_descriptors.capacity);
97 descriptor = (gsize*)sgen_array_list_get_slot (&complex_descriptors, res);
98 descriptor [0] = nwords;
99 for (i = 0; i < nwords - 1; ++i) {
100 descriptor [1 + i] = bitmap [i];
101 SGEN_LOG (6, "\tvalue: %p", (void*)descriptor [1 + i]);
108 sgen_get_complex_descriptor (SgenDescriptor desc)
110 return (gsize*) sgen_array_list_get_slot (&complex_descriptors, desc >> LOW_TYPE_BITS);
114 * Descriptor builders.
117 mono_gc_make_descr_for_object (gsize *bitmap, int numbits, size_t obj_size)
119 int first_set = -1, num_set = 0, last_set = -1, i;
120 SgenDescriptor desc = 0;
121 size_t stored_size = SGEN_ALIGN_UP (obj_size);
123 for (i = 0; i < numbits; ++i) {
124 if (bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
133 SGEN_LOG (6, "Ptrfree descriptor %p, size: %zd", (void*)desc, stored_size);
134 if (stored_size <= MAX_RUNLEN_OBJECT_SIZE && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE)
135 return DESC_TYPE_SMALL_PTRFREE | stored_size;
136 return DESC_TYPE_COMPLEX_PTRFREE;
139 g_assert (!(stored_size & 0x7));
141 SGEN_ASSERT (5, stored_size == SGEN_ALIGN_UP (stored_size), "Size is not aligned");
143 /* we know the 2-word header is ptr-free */
144 if (last_set < BITMAP_NUM_BITS + OBJECT_HEADER_WORDS && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE) {
145 desc = DESC_TYPE_BITMAP | ((*bitmap >> OBJECT_HEADER_WORDS) << LOW_TYPE_BITS);
146 SGEN_LOG (6, "Largebitmap descriptor %p, size: %zd, last set: %d", (void*)desc, stored_size, last_set);
150 if (stored_size <= MAX_RUNLEN_OBJECT_SIZE && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE) {
151 /* check run-length encoding first: one byte offset, one byte number of pointers
152 * on 64 bit archs, we can have 3 runs, just one on 32.
153 * It may be better to use nibbles.
155 if (first_set < 256 && num_set < 256 && (first_set + num_set == last_set + 1)) {
156 desc = DESC_TYPE_RUN_LENGTH | stored_size | (first_set << 16) | (num_set << 24);
157 SGEN_LOG (6, "Runlen descriptor %p, size: %zd, first set: %d, num set: %d", (void*)desc, stored_size, first_set, num_set);
162 /* it's a complex object ... */
163 desc = DESC_TYPE_COMPLEX | (alloc_complex_descriptor (bitmap, last_set + 1) << LOW_TYPE_BITS);
167 /* If the array holds references, numbits == 1 and the first bit is set in elem_bitmap */
169 mono_gc_make_descr_for_array (int vector, gsize *elem_bitmap, int numbits, size_t elem_size)
171 int first_set = -1, num_set = 0, last_set = -1, i;
172 SgenDescriptor desc = DESC_TYPE_VECTOR | (vector ? VECTOR_KIND_SZARRAY : VECTOR_KIND_ARRAY);
173 for (i = 0; i < numbits; ++i) {
174 if (elem_bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
183 if (elem_size <= MAX_ELEMENT_SIZE)
184 return desc | VECTOR_SUBTYPE_PTRFREE | (elem_size << VECTOR_ELSIZE_SHIFT);
185 return DESC_TYPE_COMPLEX_PTRFREE;
188 if (elem_size <= MAX_ELEMENT_SIZE) {
189 desc |= elem_size << VECTOR_ELSIZE_SHIFT;
191 return desc | VECTOR_SUBTYPE_PTRFREE;
193 /* Note: we also handle structs with just ref fields */
194 if (num_set * sizeof (gpointer) == elem_size) {
195 return desc | VECTOR_SUBTYPE_REFS | ((gsize)(-1) << 16);
197 /* FIXME: try run-len first */
198 /* Note: we can't skip the object header here, because it's not present */
199 if (last_set < VECTOR_BITMAP_SIZE) {
200 return desc | VECTOR_SUBTYPE_BITMAP | (*elem_bitmap << 16);
203 /* it's am array of complex structs ... */
204 desc = DESC_TYPE_COMPLEX_ARR;
205 desc |= alloc_complex_descriptor (elem_bitmap, last_set + 1) << LOW_TYPE_BITS;
209 /* Return the bitmap encoded by a descriptor */
211 mono_gc_get_bitmap_for_descr (SgenDescriptor descr, int *numbits)
213 SgenDescriptor d = (SgenDescriptor)descr;
216 switch (d & DESC_TYPE_MASK) {
217 case DESC_TYPE_RUN_LENGTH: {
218 int first_set = (d >> 16) & 0xff;
219 int num_set = (d >> 24) & 0xff;
222 bitmap = g_new0 (gsize, (first_set + num_set + 7) / 8);
224 for (i = first_set; i < first_set + num_set; ++i)
225 bitmap [i / GC_BITS_PER_WORD] |= ((gsize)1 << (i % GC_BITS_PER_WORD));
227 *numbits = first_set + num_set;
232 case DESC_TYPE_BITMAP: {
233 gsize bmap = (d >> LOW_TYPE_BITS) << OBJECT_HEADER_WORDS;
235 bitmap = g_new0 (gsize, 1);
245 case DESC_TYPE_COMPLEX: {
246 gsize *bitmap_data = sgen_get_complex_descriptor (d);
247 int bwords = (int)(*bitmap_data) - 1;//Max scalar object size is 1Mb, which means up to 32k descriptor words
250 bitmap = g_new0 (gsize, bwords);
251 *numbits = bwords * GC_BITS_PER_WORD;
253 for (i = 0; i < bwords; ++i) {
254 bitmap [i] = bitmap_data [i + 1];
261 g_assert_not_reached ();
266 mono_gc_make_descr_from_bitmap (gsize *bitmap, int numbits)
269 return MAKE_ROOT_DESC (ROOT_DESC_BITMAP, 0);
270 } else if (numbits < ((sizeof (*bitmap) * 8) - ROOT_DESC_TYPE_SHIFT)) {
271 return MAKE_ROOT_DESC (ROOT_DESC_BITMAP, bitmap [0]);
273 SgenDescriptor complex = alloc_complex_descriptor (bitmap, numbits);
274 return MAKE_ROOT_DESC (ROOT_DESC_COMPLEX, complex);
279 mono_gc_make_root_descr_all_refs (int numbits)
282 SgenDescriptor descr;
283 int num_bytes = numbits / 8;
285 if (numbits < 32 && all_ref_root_descrs [numbits])
286 return all_ref_root_descrs [numbits];
288 gc_bitmap = (gsize *)g_malloc0 (ALIGN_TO (ALIGN_TO (numbits, 8) + 1, sizeof (gsize)));
289 memset (gc_bitmap, 0xff, num_bytes);
290 if (numbits < ((sizeof (*gc_bitmap) * 8) - ROOT_DESC_TYPE_SHIFT))
291 gc_bitmap[0] = GUINT64_TO_LE(gc_bitmap[0]);
292 else if (numbits && num_bytes % (sizeof (*gc_bitmap)))
293 gc_bitmap[num_bytes / 8] = GUINT64_TO_LE(gc_bitmap [num_bytes / 8]);
295 gc_bitmap [numbits / 8] = (1 << (numbits % 8)) - 1;
296 descr = mono_gc_make_descr_from_bitmap (gc_bitmap, numbits);
300 all_ref_root_descrs [numbits] = descr;
306 sgen_make_user_root_descriptor (SgenUserRootMarkFunc marker)
308 SgenDescriptor descr;
310 g_assert (user_descriptors_next < MAX_USER_DESCRIPTORS);
311 descr = MAKE_ROOT_DESC (ROOT_DESC_USER, (SgenDescriptor)user_descriptors_next);
312 user_descriptors [user_descriptors_next ++] = marker;
318 sgen_get_complex_descriptor_bitmap (SgenDescriptor desc)
320 return (void*) sgen_array_list_get_slot (&complex_descriptors, desc >> ROOT_DESC_TYPE_SHIFT);
324 sgen_get_user_descriptor_func (SgenDescriptor desc)
326 return user_descriptors [desc >> ROOT_DESC_TYPE_SHIFT];
329 #ifdef HEAVY_STATISTICS
331 sgen_descriptor_count_scanned_object (SgenDescriptor desc)
333 int type = desc & DESC_TYPE_MASK;
334 SGEN_ASSERT (0, type, "Descriptor type can't be zero");
335 ++stat_scanned_count_per_descriptor [type - 1];
339 sgen_descriptor_count_copied_object (SgenDescriptor desc)
341 int type = desc & DESC_TYPE_MASK;
342 SGEN_ASSERT (0, type, "Descriptor type can't be zero");
343 ++stat_copied_count_per_descriptor [type - 1];
348 sgen_init_descriptors (void)
350 #ifdef HEAVY_STATISTICS
351 mono_counters_register ("# scanned RUN_LENGTH", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_RUN_LENGTH - 1]);
352 mono_counters_register ("# scanned SMALL_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_SMALL_PTRFREE - 1]);
353 mono_counters_register ("# scanned COMPLEX", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX - 1]);
354 mono_counters_register ("# scanned VECTOR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_VECTOR - 1]);
355 mono_counters_register ("# scanned BITMAP", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_BITMAP - 1]);
356 mono_counters_register ("# scanned COMPLEX_ARR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_ARR - 1]);
357 mono_counters_register ("# scanned COMPLEX_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_PTRFREE - 1]);
359 mono_counters_register ("# copied RUN_LENGTH", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_RUN_LENGTH - 1]);
360 mono_counters_register ("# copied SMALL_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_SMALL_PTRFREE - 1]);
361 mono_counters_register ("# copied COMPLEX", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX - 1]);
362 mono_counters_register ("# copied VECTOR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_VECTOR - 1]);
363 mono_counters_register ("# copied BITMAP", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_BITMAP - 1]);
364 mono_counters_register ("# copied COMPLEX_ARR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX_ARR - 1]);
365 mono_counters_register ("# copied COMPLEX_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX_PTRFREE - 1]);