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"
37 #define MAX_USER_DESCRIPTORS 16
39 #define MAKE_ROOT_DESC(type,val) ((type) | ((val) << ROOT_DESC_TYPE_SHIFT))
40 #define ALIGN_TO(val,align) ((((guint64)val) + ((align) - 1)) & ~((align) - 1))
43 static gsize* complex_descriptors = NULL;
44 static int complex_descriptors_size = 0;
45 static int complex_descriptors_next = 0;
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)
60 numbits = ALIGN_TO (numbits, GC_BITS_PER_WORD);
61 nwords = numbits / GC_BITS_PER_WORD + 1;
64 res = complex_descriptors_next;
65 /* linear search, so we don't have duplicates with domain load/unload
66 * this should not be performance critical or we'd have bigger issues
67 * (the number and size of complex descriptors should be small).
69 for (i = 0; i < complex_descriptors_next; ) {
70 if (complex_descriptors [i] == nwords) {
72 for (j = 0; j < nwords - 1; ++j) {
73 if (complex_descriptors [i + 1 + j] != bitmap [j]) {
83 i += (int)complex_descriptors [i];
85 if (complex_descriptors_next + nwords > complex_descriptors_size) {
86 int new_size = complex_descriptors_size * 2 + nwords;
87 complex_descriptors = (gsize *)g_realloc (complex_descriptors, new_size * sizeof (gsize));
88 complex_descriptors_size = new_size;
90 SGEN_LOG (6, "Complex descriptor %d, size: %d (total desc memory: %d)", res, nwords, complex_descriptors_size);
91 complex_descriptors_next += nwords;
92 complex_descriptors [res] = nwords;
93 for (i = 0; i < nwords - 1; ++i) {
94 complex_descriptors [res + 1 + i] = bitmap [i];
95 SGEN_LOG (6, "\tvalue: %p", (void*)complex_descriptors [res + 1 + i]);
102 sgen_get_complex_descriptor (SgenDescriptor desc)
104 return complex_descriptors + (desc >> LOW_TYPE_BITS);
108 * Descriptor builders.
111 mono_gc_make_descr_for_object (gsize *bitmap, int numbits, size_t obj_size)
113 int first_set = -1, num_set = 0, last_set = -1, i;
114 SgenDescriptor desc = 0;
115 size_t stored_size = SGEN_ALIGN_UP (obj_size);
117 for (i = 0; i < numbits; ++i) {
118 if (bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
127 SGEN_LOG (6, "Ptrfree descriptor %p, size: %zd", (void*)desc, stored_size);
128 if (stored_size <= MAX_RUNLEN_OBJECT_SIZE && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE)
129 return DESC_TYPE_SMALL_PTRFREE | stored_size;
130 return DESC_TYPE_COMPLEX_PTRFREE;
133 g_assert (!(stored_size & 0x7));
135 SGEN_ASSERT (5, stored_size == SGEN_ALIGN_UP (stored_size), "Size is not aligned");
137 /* we know the 2-word header is ptr-free */
138 if (last_set < BITMAP_NUM_BITS + OBJECT_HEADER_WORDS && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE) {
139 desc = DESC_TYPE_BITMAP | ((*bitmap >> OBJECT_HEADER_WORDS) << LOW_TYPE_BITS);
140 SGEN_LOG (6, "Largebitmap descriptor %p, size: %zd, last set: %d", (void*)desc, stored_size, last_set);
144 if (stored_size <= MAX_RUNLEN_OBJECT_SIZE && stored_size <= SGEN_MAX_SMALL_OBJ_SIZE) {
145 /* check run-length encoding first: one byte offset, one byte number of pointers
146 * on 64 bit archs, we can have 3 runs, just one on 32.
147 * It may be better to use nibbles.
149 if (first_set < 256 && num_set < 256 && (first_set + num_set == last_set + 1)) {
150 desc = DESC_TYPE_RUN_LENGTH | stored_size | (first_set << 16) | (num_set << 24);
151 SGEN_LOG (6, "Runlen descriptor %p, size: %zd, first set: %d, num set: %d", (void*)desc, stored_size, first_set, num_set);
156 /* it's a complex object ... */
157 desc = DESC_TYPE_COMPLEX | (alloc_complex_descriptor (bitmap, last_set + 1) << LOW_TYPE_BITS);
161 /* If the array holds references, numbits == 1 and the first bit is set in elem_bitmap */
163 mono_gc_make_descr_for_array (int vector, gsize *elem_bitmap, int numbits, size_t elem_size)
165 int first_set = -1, num_set = 0, last_set = -1, i;
166 SgenDescriptor desc = DESC_TYPE_VECTOR | (vector ? VECTOR_KIND_SZARRAY : VECTOR_KIND_ARRAY);
167 for (i = 0; i < numbits; ++i) {
168 if (elem_bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
177 if (elem_size <= MAX_ELEMENT_SIZE)
178 return desc | VECTOR_SUBTYPE_PTRFREE | (elem_size << VECTOR_ELSIZE_SHIFT);
179 return DESC_TYPE_COMPLEX_PTRFREE;
182 if (elem_size <= MAX_ELEMENT_SIZE) {
183 desc |= elem_size << VECTOR_ELSIZE_SHIFT;
185 return desc | VECTOR_SUBTYPE_PTRFREE;
187 /* Note: we also handle structs with just ref fields */
188 if (num_set * sizeof (gpointer) == elem_size) {
189 return desc | VECTOR_SUBTYPE_REFS | ((gssize)(-1) << 16);
191 /* FIXME: try run-len first */
192 /* Note: we can't skip the object header here, because it's not present */
193 if (last_set < VECTOR_BITMAP_SIZE) {
194 return desc | VECTOR_SUBTYPE_BITMAP | (*elem_bitmap << 16);
197 /* it's am array of complex structs ... */
198 desc = DESC_TYPE_COMPLEX_ARR;
199 desc |= alloc_complex_descriptor (elem_bitmap, last_set + 1) << LOW_TYPE_BITS;
203 /* Return the bitmap encoded by a descriptor */
205 mono_gc_get_bitmap_for_descr (SgenDescriptor descr, int *numbits)
207 SgenDescriptor d = (SgenDescriptor)descr;
210 switch (d & DESC_TYPE_MASK) {
211 case DESC_TYPE_RUN_LENGTH: {
212 int first_set = (d >> 16) & 0xff;
213 int num_set = (d >> 24) & 0xff;
216 bitmap = g_new0 (gsize, (first_set + num_set + 7) / 8);
218 for (i = first_set; i < first_set + num_set; ++i)
219 bitmap [i / GC_BITS_PER_WORD] |= ((gsize)1 << (i % GC_BITS_PER_WORD));
221 *numbits = first_set + num_set;
226 case DESC_TYPE_BITMAP: {
227 gsize bmap = (d >> LOW_TYPE_BITS) << OBJECT_HEADER_WORDS;
229 bitmap = g_new0 (gsize, 1);
239 case DESC_TYPE_COMPLEX: {
240 gsize *bitmap_data = sgen_get_complex_descriptor (d);
241 int bwords = (int)(*bitmap_data) - 1;//Max scalar object size is 1Mb, which means up to 32k descriptor words
244 bitmap = g_new0 (gsize, bwords);
245 *numbits = bwords * GC_BITS_PER_WORD;
247 for (i = 0; i < bwords; ++i) {
248 bitmap [i] = bitmap_data [i + 1];
255 g_assert_not_reached ();
260 mono_gc_make_descr_from_bitmap (gsize *bitmap, int numbits)
263 return MAKE_ROOT_DESC (ROOT_DESC_BITMAP, 0);
264 } else if (numbits < ((sizeof (*bitmap) * 8) - ROOT_DESC_TYPE_SHIFT)) {
265 return MAKE_ROOT_DESC (ROOT_DESC_BITMAP, bitmap [0]);
267 SgenDescriptor complex = alloc_complex_descriptor (bitmap, numbits);
268 return MAKE_ROOT_DESC (ROOT_DESC_COMPLEX, complex);
273 mono_gc_make_root_descr_all_refs (int numbits)
276 SgenDescriptor descr;
277 int num_bytes = numbits / 8;
279 if (numbits < 32 && all_ref_root_descrs [numbits])
280 return all_ref_root_descrs [numbits];
282 gc_bitmap = (gsize *)g_malloc0 (ALIGN_TO (ALIGN_TO (numbits, 8) + 1, sizeof (gsize)));
283 memset (gc_bitmap, 0xff, num_bytes);
284 if (numbits < ((sizeof (*gc_bitmap) * 8) - ROOT_DESC_TYPE_SHIFT))
285 gc_bitmap[0] = GUINT64_TO_LE(gc_bitmap[0]);
286 else if (numbits && num_bytes % (sizeof (*gc_bitmap)))
287 gc_bitmap[num_bytes / 8] = GUINT64_TO_LE(gc_bitmap [num_bytes / 8]);
289 gc_bitmap [numbits / 8] = (1 << (numbits % 8)) - 1;
290 descr = mono_gc_make_descr_from_bitmap (gc_bitmap, numbits);
294 all_ref_root_descrs [numbits] = descr;
300 sgen_make_user_root_descriptor (SgenUserRootMarkFunc marker)
302 SgenDescriptor descr;
304 g_assert (user_descriptors_next < MAX_USER_DESCRIPTORS);
305 descr = MAKE_ROOT_DESC (ROOT_DESC_USER, (SgenDescriptor)user_descriptors_next);
306 user_descriptors [user_descriptors_next ++] = marker;
312 sgen_get_complex_descriptor_bitmap (SgenDescriptor desc)
314 return complex_descriptors + (desc >> ROOT_DESC_TYPE_SHIFT);
318 sgen_get_user_descriptor_func (SgenDescriptor desc)
320 return user_descriptors [desc >> ROOT_DESC_TYPE_SHIFT];
323 #ifdef HEAVY_STATISTICS
325 sgen_descriptor_count_scanned_object (SgenDescriptor desc)
327 int type = desc & DESC_TYPE_MASK;
328 SGEN_ASSERT (0, type, "Descriptor type can't be zero");
329 ++stat_scanned_count_per_descriptor [type - 1];
333 sgen_descriptor_count_copied_object (SgenDescriptor desc)
335 int type = desc & DESC_TYPE_MASK;
336 SGEN_ASSERT (0, type, "Descriptor type can't be zero");
337 ++stat_copied_count_per_descriptor [type - 1];
342 sgen_init_descriptors (void)
344 #ifdef HEAVY_STATISTICS
345 mono_counters_register ("# scanned RUN_LENGTH", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_RUN_LENGTH - 1]);
346 mono_counters_register ("# scanned SMALL_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_SMALL_PTRFREE - 1]);
347 mono_counters_register ("# scanned COMPLEX", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX - 1]);
348 mono_counters_register ("# scanned VECTOR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_VECTOR - 1]);
349 mono_counters_register ("# scanned BITMAP", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_BITMAP - 1]);
350 mono_counters_register ("# scanned COMPLEX_ARR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_ARR - 1]);
351 mono_counters_register ("# scanned COMPLEX_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_PTRFREE - 1]);
353 mono_counters_register ("# copied RUN_LENGTH", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_RUN_LENGTH - 1]);
354 mono_counters_register ("# copied SMALL_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_SMALL_PTRFREE - 1]);
355 mono_counters_register ("# copied COMPLEX", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX - 1]);
356 mono_counters_register ("# copied VECTOR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_VECTOR - 1]);
357 mono_counters_register ("# copied BITMAP", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_BITMAP - 1]);
358 mono_counters_register ("# copied COMPLEX_ARR", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX_ARR - 1]);
359 mono_counters_register ("# copied COMPLEX_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_copied_count_per_descriptor [DESC_TYPE_COMPLEX_PTRFREE - 1]);