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 * This library is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Library General Public
11 * License 2.0 as published by the Free Software Foundation;
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Library General Public License for more details.
18 * You should have received a copy of the GNU Library General Public
19 * License 2.0 along with this library; if not, write to the Free
20 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
31 #ifdef HAVE_SEMAPHORE_H
32 #include <semaphore.h>
46 #include "utils/mono-counters.h"
47 #include "metadata/sgen-gc.h"
49 #define MAX_USER_DESCRIPTORS 16
51 #define MAKE_ROOT_DESC(type,val) ((type) | ((val) << ROOT_DESC_TYPE_SHIFT))
52 #define ALIGN_TO(val,align) ((((guint64)val) + ((align) - 1)) & ~((align) - 1))
55 static gsize* complex_descriptors = NULL;
56 static int complex_descriptors_size = 0;
57 static int complex_descriptors_next = 0;
58 static MonoGCRootMarkFunc user_descriptors [MAX_USER_DESCRIPTORS];
59 static int user_descriptors_next = 0;
60 static void *all_ref_root_descrs [32];
62 #ifdef HEAVY_STATISTICS
63 static long long stat_scanned_count_per_descriptor [DESC_TYPE_MAX];
67 alloc_complex_descriptor (gsize *bitmap, int numbits)
71 numbits = ALIGN_TO (numbits, GC_BITS_PER_WORD);
72 nwords = numbits / GC_BITS_PER_WORD + 1;
75 res = complex_descriptors_next;
76 /* linear search, so we don't have duplicates with domain load/unload
77 * this should not be performance critical or we'd have bigger issues
78 * (the number and size of complex descriptors should be small).
80 for (i = 0; i < complex_descriptors_next; ) {
81 if (complex_descriptors [i] == nwords) {
83 for (j = 0; j < nwords - 1; ++j) {
84 if (complex_descriptors [i + 1 + j] != bitmap [j]) {
94 i += (int)complex_descriptors [i];
96 if (complex_descriptors_next + nwords > complex_descriptors_size) {
97 int new_size = complex_descriptors_size * 2 + nwords;
98 complex_descriptors = g_realloc (complex_descriptors, new_size * sizeof (gsize));
99 complex_descriptors_size = new_size;
101 SGEN_LOG (6, "Complex descriptor %d, size: %d (total desc memory: %d)", res, nwords, complex_descriptors_size);
102 complex_descriptors_next += nwords;
103 complex_descriptors [res] = nwords;
104 for (i = 0; i < nwords - 1; ++i) {
105 complex_descriptors [res + 1 + i] = bitmap [i];
106 SGEN_LOG (6, "\tvalue: %p", (void*)complex_descriptors [res + 1 + i]);
113 sgen_get_complex_descriptor (mword desc)
115 return complex_descriptors + (desc >> LOW_TYPE_BITS);
119 * Descriptor builders.
122 mono_gc_make_descr_for_string (gsize *bitmap, int numbits)
124 return (void*) DESC_TYPE_RUN_LENGTH;
128 mono_gc_make_descr_for_object (gsize *bitmap, int numbits, size_t obj_size)
130 int first_set = -1, num_set = 0, last_set = -1, i;
132 size_t stored_size = obj_size;
134 stored_size += SGEN_ALLOC_ALIGN - 1;
135 stored_size &= ~(SGEN_ALLOC_ALIGN - 1);
137 for (i = 0; i < numbits; ++i) {
138 if (bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
147 SGEN_LOG (6, "Ptrfree descriptor %p, size: %zd", (void*)desc, stored_size);
148 if (stored_size <= MAX_RUNLEN_OBJECT_SIZE)
149 return (void*)(DESC_TYPE_RUN_LENGTH | stored_size);
150 return (void*)DESC_TYPE_COMPLEX_PTRFREE;
153 g_assert (!(stored_size & 0x7));
155 if (stored_size <= MAX_RUNLEN_OBJECT_SIZE) {
156 /* check run-length encoding first: one byte offset, one byte number of pointers
157 * on 64 bit archs, we can have 3 runs, just one on 32.
158 * It may be better to use nibbles.
160 if (first_set < 256 && num_set < 256 && (first_set + num_set == last_set + 1)) {
161 desc = DESC_TYPE_RUN_LENGTH | stored_size | (first_set << 16) | (num_set << 24);
162 SGEN_LOG (6, "Runlen descriptor %p, size: %zd, first set: %d, num set: %d", (void*)desc, stored_size, first_set, num_set);
167 /* we know the 2-word header is ptr-free */
168 if (last_set < SMALL_BITMAP_SIZE + OBJECT_HEADER_WORDS && stored_size < (1 << SMALL_BITMAP_SHIFT)) {
169 desc = DESC_TYPE_SMALL_BITMAP | stored_size | ((*bitmap >> OBJECT_HEADER_WORDS) << SMALL_BITMAP_SHIFT);
170 SGEN_LOG (6, "Smallbitmap descriptor %p, size: %zd, last set: %d", (void*)desc, stored_size, last_set);
174 /* we know the 2-word header is ptr-free */
175 if (last_set < LARGE_BITMAP_SIZE + OBJECT_HEADER_WORDS) {
176 desc = DESC_TYPE_LARGE_BITMAP | ((*bitmap >> OBJECT_HEADER_WORDS) << LOW_TYPE_BITS);
177 SGEN_LOG (6, "Largebitmap descriptor %p, size: %zd, last set: %d", (void*)desc, stored_size, last_set);
180 /* it's a complex object ... */
181 desc = DESC_TYPE_COMPLEX | (alloc_complex_descriptor (bitmap, last_set + 1) << LOW_TYPE_BITS);
185 /* If the array holds references, numbits == 1 and the first bit is set in elem_bitmap */
187 mono_gc_make_descr_for_array (int vector, gsize *elem_bitmap, int numbits, size_t elem_size)
189 int first_set = -1, num_set = 0, last_set = -1, i;
190 mword desc = DESC_TYPE_VECTOR | (vector ? VECTOR_KIND_SZARRAY : VECTOR_KIND_ARRAY);
191 for (i = 0; i < numbits; ++i) {
192 if (elem_bitmap [i / GC_BITS_PER_WORD] & ((gsize)1 << (i % GC_BITS_PER_WORD))) {
201 if (elem_size <= MAX_ELEMENT_SIZE)
202 return (void*)(desc | VECTOR_SUBTYPE_PTRFREE | (elem_size << VECTOR_ELSIZE_SHIFT));
203 return (void*)DESC_TYPE_COMPLEX_PTRFREE;
206 if (elem_size <= MAX_ELEMENT_SIZE) {
207 desc |= elem_size << VECTOR_ELSIZE_SHIFT;
209 return (void*)(desc | VECTOR_SUBTYPE_PTRFREE);
211 /* Note: we also handle structs with just ref fields */
212 if (num_set * sizeof (gpointer) == elem_size) {
213 return (void*)(desc | VECTOR_SUBTYPE_REFS | ((gssize)(-1) << 16));
215 /* FIXME: try run-len first */
216 /* Note: we can't skip the object header here, because it's not present */
217 if (last_set < SMALL_BITMAP_SIZE) {
218 return (void*)(desc | VECTOR_SUBTYPE_BITMAP | (*elem_bitmap << 16));
221 /* it's am array of complex structs ... */
222 desc = DESC_TYPE_COMPLEX_ARR;
223 desc |= alloc_complex_descriptor (elem_bitmap, last_set + 1) << LOW_TYPE_BITS;
227 /* Return the bitmap encoded by a descriptor */
229 mono_gc_get_bitmap_for_descr (void *descr, int *numbits)
231 mword d = (mword)descr;
235 case DESC_TYPE_RUN_LENGTH: {
236 int first_set = (d >> 16) & 0xff;
237 int num_set = (d >> 24) & 0xff;
240 bitmap = g_new0 (gsize, (first_set + num_set + 7) / 8);
242 for (i = first_set; i < first_set + num_set; ++i)
243 bitmap [i / GC_BITS_PER_WORD] |= ((gsize)1 << (i % GC_BITS_PER_WORD));
245 *numbits = first_set + num_set;
250 case DESC_TYPE_SMALL_BITMAP:
251 bitmap = g_new0 (gsize, 1);
253 bitmap [0] = (d >> SMALL_BITMAP_SHIFT) << OBJECT_HEADER_WORDS;
255 *numbits = GC_BITS_PER_WORD;
258 case DESC_TYPE_LARGE_BITMAP: {
259 gsize bmap = (d >> LOW_TYPE_BITS) << OBJECT_HEADER_WORDS;
261 bitmap = g_new0 (gsize, 1);
271 case DESC_TYPE_COMPLEX: {
272 gsize *bitmap_data = sgen_get_complex_descriptor (d);
273 int bwords = (int)(*bitmap_data) - 1;//Max scalar object size is 1Mb, which means up to 32k descriptor words
276 bitmap = g_new0 (gsize, bwords);
277 *numbits = bwords * GC_BITS_PER_WORD;
279 for (i = 0; i < bwords; ++i) {
280 bitmap [i] = bitmap_data [i + 1];
287 g_assert_not_reached ();
292 mono_gc_make_descr_from_bitmap (gsize *bitmap, int numbits)
295 return (void*)MAKE_ROOT_DESC (ROOT_DESC_BITMAP, 0);
296 } else if (numbits < ((sizeof (*bitmap) * 8) - ROOT_DESC_TYPE_SHIFT)) {
297 return (void*)MAKE_ROOT_DESC (ROOT_DESC_BITMAP, bitmap [0]);
299 mword complex = alloc_complex_descriptor (bitmap, numbits);
300 return (void*)MAKE_ROOT_DESC (ROOT_DESC_COMPLEX, complex);
305 mono_gc_make_root_descr_all_refs (int numbits)
309 int num_bytes = numbits / 8;
311 if (numbits < 32 && all_ref_root_descrs [numbits])
312 return all_ref_root_descrs [numbits];
314 gc_bitmap = g_malloc0 (ALIGN_TO (ALIGN_TO (numbits, 8) + 1, sizeof (gsize)));
315 memset (gc_bitmap, 0xff, num_bytes);
316 if (numbits < ((sizeof (*gc_bitmap) * 8) - ROOT_DESC_TYPE_SHIFT))
317 gc_bitmap[0] = GUINT64_TO_LE(gc_bitmap[0]);
318 else if (numbits && num_bytes % (sizeof (*gc_bitmap)))
319 gc_bitmap[num_bytes / 8] = GUINT64_TO_LE(gc_bitmap [num_bytes / 8]);
321 gc_bitmap [numbits / 8] = (1 << (numbits % 8)) - 1;
322 descr = mono_gc_make_descr_from_bitmap (gc_bitmap, numbits);
326 all_ref_root_descrs [numbits] = descr;
332 mono_gc_make_root_descr_user (MonoGCRootMarkFunc marker)
336 g_assert (user_descriptors_next < MAX_USER_DESCRIPTORS);
337 descr = (void*)MAKE_ROOT_DESC (ROOT_DESC_USER, (mword)user_descriptors_next);
338 user_descriptors [user_descriptors_next ++] = marker;
344 sgen_get_complex_descriptor_bitmap (mword desc)
346 return complex_descriptors + (desc >> ROOT_DESC_TYPE_SHIFT);
350 sgen_get_user_descriptor_func (mword desc)
352 return user_descriptors [desc >> ROOT_DESC_TYPE_SHIFT];
355 #ifdef HEAVY_STATISTICS
357 sgen_descriptor_count_scanned_object (mword desc)
360 SGEN_ASSERT (0, type, "Descriptor type can't be zero");
361 ++stat_scanned_count_per_descriptor [type - 1];
366 sgen_init_descriptors (void)
368 #ifdef HEAVY_STATISTICS
369 mono_counters_register ("# scanned RUN_LENGTH", MONO_COUNTER_GC | MONO_COUNTER_LONG, &stat_scanned_count_per_descriptor [DESC_TYPE_RUN_LENGTH - 1]);
370 mono_counters_register ("# scanned SMALL_BITMAP", MONO_COUNTER_GC | MONO_COUNTER_LONG, &stat_scanned_count_per_descriptor [DESC_TYPE_SMALL_BITMAP - 1]);
371 mono_counters_register ("# scanned COMPLEX", MONO_COUNTER_GC | MONO_COUNTER_LONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX - 1]);
372 mono_counters_register ("# scanned VECTOR", MONO_COUNTER_GC | MONO_COUNTER_LONG, &stat_scanned_count_per_descriptor [DESC_TYPE_VECTOR - 1]);
373 mono_counters_register ("# scanned LARGE_BITMAP", MONO_COUNTER_GC | MONO_COUNTER_LONG, &stat_scanned_count_per_descriptor [DESC_TYPE_LARGE_BITMAP - 1]);
374 mono_counters_register ("# scanned COMPLEX_ARR", MONO_COUNTER_GC | MONO_COUNTER_LONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_ARR - 1]);
375 mono_counters_register ("# scanned COMPLEX_PTRFREE", MONO_COUNTER_GC | MONO_COUNTER_LONG, &stat_scanned_count_per_descriptor [DESC_TYPE_COMPLEX_PTRFREE - 1]);