mono/metadata/sgen-nursery-allocator.c

   1 /*
   2  * sgen-nursery-allocator.c: Nursery allocation code.
   3  *
   4  * Copyright 2009-2010 Novell, Inc.
   5  *           2011 Rodrigo Kumpera
   6  *
   7  * Copyright 2011 Xamarin Inc  (http://www.xamarin.com)
   8  * Copyright (C) 2012 Xamarin Inc
   9  *
  10  * This library is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU Library General Public
  12  * License 2.0 as published by the Free Software Foundation;
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Library General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Library General Public
  20  * License 2.0 along with this library; if not, write to the Free
  21  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  22  */
  23
  24 /*
  25  * The young generation is divided into fragments. This is because
  26  * we can hand one fragments to a thread for lock-less fast alloc and
  27  * because the young generation ends up fragmented anyway by pinned objects.
  28  * Once a collection is done, a list of fragments is created. When doing
  29  * thread local alloc we use smallish nurseries so we allow new threads to
  30  * allocate memory from gen0 without triggering a collection. Threads that
  31  * are found to allocate lots of memory are given bigger fragments. This
  32  * should make the finalizer thread use little nursery memory after a while.
  33  * We should start assigning threads very small fragments: if there are many
  34  * threads the nursery will be full of reserved space that the threads may not
  35  * use at all, slowing down allocation speed.
  36  * Thread local allocation is done from areas of memory Hotspot calls Thread Local
  37  * Allocation Buffers (TLABs).
  38  */
  39 #include "config.h"
  40 #ifdef HAVE_SGEN_GC
  41
  42 #ifdef HAVE_UNISTD_H
  43 #include <unistd.h>
  44 #endif
  45 #ifdef HAVE_PTHREAD_H
  46 #include <pthread.h>
  47 #endif
  48 #ifdef HAVE_SEMAPHORE_H
  49 #include <semaphore.h>
  50 #endif
  51 #include <stdio.h>
  52 #include <string.h>
  53 #include <errno.h>
  54 #include <assert.h>
  55 #ifdef __MACH__
  56 #undef _XOPEN_SOURCE
  57 #endif
  58 #ifdef __MACH__
  59 #define _XOPEN_SOURCE
  60 #endif
  61
  62 #include "metadata/sgen-gc.h"
  63 #include "metadata/metadata-internals.h"
  64 #include "metadata/class-internals.h"
  65 #include "metadata/gc-internal.h"
  66 #include "metadata/object-internals.h"
  67 #include "metadata/threads.h"
  68 #include "metadata/sgen-cardtable.h"
  69 #include "metadata/sgen-protocol.h"
  70 #include "metadata/sgen-archdep.h"
  71 #include "metadata/sgen-bridge.h"
  72 #include "metadata/sgen-memory-governor.h"
  73 #include "metadata/sgen-pinning.h"
  74 #include "metadata/mono-gc.h"
  75 #include "metadata/method-builder.h"
  76 #include "metadata/profiler-private.h"
  77 #include "metadata/monitor.h"
  78 #include "metadata/threadpool-internals.h"
  79 #include "metadata/mempool-internals.h"
  80 #include "metadata/marshal.h"
  81 #include "utils/mono-mmap.h"
  82 #include "utils/mono-time.h"
  83 #include "utils/mono-semaphore.h"
  84 #include "utils/mono-counters.h"
  85 #include "utils/mono-proclib.h"
  86 #include "utils/mono-threads.h"
  87
  88 /* Enable it so nursery allocation diagnostic data is collected */
  89 //#define NALLOC_DEBUG 1
  90
  91 /* The mutator allocs from here. */
  92 SgenFragmentAllocator mutator_allocator;
  93
  94 /* freeelist of fragment structures */
  95 static SgenFragment *fragment_freelist = NULL;
  96
  97 /* Allocator cursors */
  98 static char *nursery_last_pinned_end = NULL;
  99
 100 char *sgen_nursery_start;
 101 char *sgen_nursery_end;
 102
 103 #ifdef USER_CONFIG
 104 size_t sgen_nursery_size = (1 << 22);
 105 int sgen_nursery_bits = 22;
 106 #endif
 107
 108 char *sgen_space_bitmap;
 109 size_t sgen_space_bitmap_size;
 110
 111 #ifdef HEAVY_STATISTICS
 112
 113 static gint32 stat_wasted_bytes_trailer = 0;
 114 static gint32 stat_wasted_bytes_small_areas = 0;
 115 static gint32 stat_wasted_bytes_discarded_fragments = 0;
 116 static gint32 stat_nursery_alloc_requests = 0;
 117 static gint32 stat_alloc_iterations = 0;
 118 static gint32 stat_alloc_retries = 0;
 119
 120 static gint32 stat_nursery_alloc_range_requests = 0;
 121 static gint32 stat_alloc_range_iterations = 0;
 122 static gint32 stat_alloc_range_retries = 0;
 123
 124 #endif
 125
 126 /************************************Nursery allocation debugging *********************************************/
 127
 128 #ifdef NALLOC_DEBUG
 129
 130 enum {
 131         FIXED_ALLOC = 1,
 132         RANGE_ALLOC,
 133         PINNING,
 134         BLOCK_ZEROING,
 135         CLEAR_NURSERY_FRAGS
 136 };
 137
 138 typedef struct {
 139         char *address;
 140         size_t size;
 141         int reason;
 142         int seq;
 143         MonoNativeThreadId tid;
 144 } AllocRecord;
 145
 146 #define ALLOC_RECORD_COUNT 128000
 147
 148
 149 static AllocRecord *alloc_records;
 150 static volatile int next_record;
 151 static volatile int alloc_count;
 152
 153 void dump_alloc_records (void);
 154 void verify_alloc_records (void);
 155
 156 static const char*
 157 get_reason_name (AllocRecord *rec)
 158 {
 159         switch (rec->reason) {
 160         case FIXED_ALLOC: return "fixed-alloc";
 161         case RANGE_ALLOC: return "range-alloc";
 162         case PINNING: return "pinning";
 163         case BLOCK_ZEROING: return "block-zeroing";
 164         case CLEAR_NURSERY_FRAGS: return "clear-nursery-frag";
 165         default: return "invalid";
 166         }
 167 }
 168
 169 static void
 170 reset_alloc_records (void)
 171 {
 172         next_record = 0;
 173         alloc_count = 0;
 174 }
 175
 176 static void
 177 add_alloc_record (char *addr, size_t size, int reason)
 178 {
 179         int idx = InterlockedIncrement (&next_record) - 1;
 180         alloc_records [idx].address = addr;
 181         alloc_records [idx].size = size;
 182         alloc_records [idx].reason = reason;
 183         alloc_records [idx].seq = idx;
 184         alloc_records [idx].tid = mono_native_thread_id_get ();
 185 }
 186
 187 static int
 188 comp_alloc_record (const void *_a, const void *_b)
 189 {
 190         const AllocRecord *a = _a;
 191         const AllocRecord *b = _b;
 192         if (a->address == b->address)
 193                 return a->seq - b->seq;
 194         return a->address - b->address;
 195 }
 196
 197 #define rec_end(REC) ((REC)->address + (REC)->size)
 198
 199 void
 200 dump_alloc_records (void)
 201 {
 202         int i;
 203         sgen_qsort (alloc_records, next_record, sizeof (AllocRecord), comp_alloc_record);
 204
 205         printf ("------------------------------------DUMP RECORDS----------------------------\n");
 206         for (i = 0; i < next_record; ++i) {
 207                 AllocRecord *rec = alloc_records + i;
 208                 printf ("obj [%p, %p] size %d reason %s seq %d tid %x\n", rec->address, rec_end (rec), (int)rec->size, get_reason_name (rec), rec->seq, (size_t)rec->tid);
 209         }
 210 }
 211
 212 void
 213 verify_alloc_records (void)
 214 {
 215         int i;
 216         int total = 0;
 217         int holes = 0;
 218         int max_hole = 0;
 219         AllocRecord *prev = NULL;
 220
 221         sgen_qsort (alloc_records, next_record, sizeof (AllocRecord), comp_alloc_record);
 222         printf ("------------------------------------DUMP RECORDS- %d %d---------------------------\n", next_record, alloc_count);
 223         for (i = 0; i < next_record; ++i) {
 224                 AllocRecord *rec = alloc_records + i;
 225                 int hole_size = 0;
 226                 total += rec->size;
 227                 if (prev) {
 228                         if (rec_end (prev) > rec->address)
 229                                 printf ("WE GOT OVERLAPPING objects %p and %p\n", prev->address, rec->address);
 230                         if ((rec->address - rec_end (prev)) >= 8)
 231                                 ++holes;
 232                         hole_size = rec->address - rec_end (prev);
 233                         max_hole = MAX (max_hole, hole_size);
 234                 }
 235                 printf ("obj [%p, %p] size %d hole to prev %d reason %s seq %d tid %zx\n", rec->address, rec_end (rec), (int)rec->size, hole_size, get_reason_name (rec), rec->seq, (size_t)rec->tid);
 236                 prev = rec;
 237         }
 238         printf ("SUMMARY total alloc'd %d holes %d max_hole %d\n", total, holes, max_hole);
 239 }
 240
 241 #endif
 242
 243 /*********************************************************************************/
 244
 245
 246 static inline gpointer
 247 mask (gpointer n, uintptr_t bit)
 248 {
 249         return (gpointer)(((uintptr_t)n) | bit);
 250 }
 251
 252 static inline gpointer
 253 unmask (gpointer p)
 254 {
 255         return (gpointer)((uintptr_t)p & ~(uintptr_t)0x3);
 256 }
 257
 258 static inline uintptr_t
 259 get_mark (gpointer n)
 260 {
 261         return (uintptr_t)n & 0x1;
 262 }
 263
 264 /*MUST be called with world stopped*/
 265 SgenFragment*
 266 sgen_fragment_allocator_alloc (void)
 267 {
 268         SgenFragment *frag = fragment_freelist;
 269         if (frag) {
 270                 fragment_freelist = frag->next_in_order;
 271                 frag->next = frag->next_in_order = NULL;
 272                 return frag;
 273         }
 274         frag = sgen_alloc_internal (INTERNAL_MEM_FRAGMENT);
 275         frag->next = frag->next_in_order = NULL;
 276         return frag;
 277 }
 278
 279 void
 280 sgen_fragment_allocator_add (SgenFragmentAllocator *allocator, char *start, char *end)
 281 {
 282         SgenFragment *fragment;
 283
 284         fragment = sgen_fragment_allocator_alloc ();
 285         fragment->fragment_start = start;
 286         fragment->fragment_next = start;
 287         fragment->fragment_end = end;
 288         fragment->next_in_order = fragment->next = unmask (allocator->region_head);
 289
 290         allocator->region_head = allocator->alloc_head = fragment;
 291         g_assert (fragment->fragment_end > fragment->fragment_start);
 292 }
 293
 294 void
 295 sgen_fragment_allocator_release (SgenFragmentAllocator *allocator)
 296 {
 297         SgenFragment *last = allocator->region_head;
 298         if (!last)
 299                 return;
 300
 301         /* Find the last fragment in insert order */
 302         for (; last->next_in_order; last = last->next_in_order) ;
 303
 304         last->next_in_order = fragment_freelist;
 305         fragment_freelist = allocator->region_head;
 306         allocator->alloc_head = allocator->region_head = NULL;
 307 }
 308
 309 static SgenFragment**
 310 find_previous_pointer_fragment (SgenFragmentAllocator *allocator, SgenFragment *frag)
 311 {
 312         SgenFragment **prev;
 313         SgenFragment *cur, *next;
 314 #ifdef NALLOC_DEBUG
 315         int count = 0;
 316 #endif
 317
 318 try_again:
 319         prev = &allocator->alloc_head;
 320 #ifdef NALLOC_DEBUG
 321         if (count++ > 5)
 322                 printf ("retry count for fppf is %d\n", count);
 323 #endif
 324
 325         cur = unmask (*prev);
 326
 327         while (1) {
 328                 if (cur == NULL)
 329                         return NULL;
 330                 next = cur->next;
 331
 332                 /*
 333                  * We need to make sure that we dereference prev below
 334                  * after reading cur->next above, so we need a read
 335                  * barrier.
 336                  */
 337                 mono_memory_read_barrier ();
 338
 339                 if (*prev != cur)
 340                         goto try_again;
 341
 342                 if (!get_mark (next)) {
 343                         if (cur == frag)
 344                                 return prev;
 345                         prev = &cur->next;
 346                 } else {
 347                         next = unmask (next);
 348                         if (InterlockedCompareExchangePointer ((volatile gpointer*)prev, next, cur) != cur)
 349                                 goto try_again;
 350                         /*we must make sure that the next from cur->next happens after*/
 351                         mono_memory_write_barrier ();
 352                 }
 353
 354                 cur = mono_lls_pointer_unmask (next);
 355         }
 356         return NULL;
 357 }
 358
 359 static gboolean
 360 claim_remaining_size (SgenFragment *frag, char *alloc_end)
 361 {
 362         /* All space used, nothing to claim. */
 363         if (frag->fragment_end <= alloc_end)
 364                 return FALSE;
 365
 366         /* Try to alloc all the remaining space. */
 367         return InterlockedCompareExchangePointer ((volatile gpointer*)&frag->fragment_next, frag->fragment_end, alloc_end) == alloc_end;
 368 }
 369
 370 static void*
 371 par_alloc_from_fragment (SgenFragmentAllocator *allocator, SgenFragment *frag, size_t size)
 372 {
 373         char *p = frag->fragment_next;
 374         char *end = p + size;
 375
 376         if (end > frag->fragment_end)
 377                 return NULL;
 378
 379         /* p = frag->fragment_next must happen before */
 380         mono_memory_barrier ();
 381
 382         if (InterlockedCompareExchangePointer ((volatile gpointer*)&frag->fragment_next, end, p) != p)
 383                 return NULL;
 384
 385         if (frag->fragment_end - end < SGEN_MAX_NURSERY_WASTE) {
 386                 SgenFragment *next, **prev_ptr;
 387
 388                 /*
 389                  * Before we clean the remaining nursery, we must claim the remaining space
 390                  * as it could end up been used by the range allocator since it can end up
 391                  * allocating from this dying fragment as it doesn't respect SGEN_MAX_NURSERY_WASTE
 392                  * when doing second chance allocation.
 393                  */
 394                 if ((sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION || sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION_DEBUG) && claim_remaining_size (frag, end)) {
 395                         sgen_clear_range (end, frag->fragment_end);
 396                         HEAVY_STAT (InterlockedExchangeAdd (&stat_wasted_bytes_trailer, frag->fragment_end - end));
 397 #ifdef NALLOC_DEBUG
 398                         add_alloc_record (end, frag->fragment_end - end, BLOCK_ZEROING);
 399 #endif
 400                 }
 401
 402                 prev_ptr = find_previous_pointer_fragment (allocator, frag);
 403
 404                 /*Use Michaels linked list remove*/
 405
 406                 /*prev_ptr will be null if the fragment was removed concurrently */
 407                 while (prev_ptr) {
 408                         next = frag->next;
 409
 410                         /*already deleted*/
 411                         if (!get_mark (next)) {
 412                                 /*frag->next read must happen before the first CAS*/
 413                                 mono_memory_write_barrier ();
 414
 415                                 /*Fail if the next node is removed concurrently and its CAS wins */
 416                                 if (InterlockedCompareExchangePointer ((volatile gpointer*)&frag->next, mask (next, 1), next) != next) {
 417                                         continue;
 418                                 }
 419                         }
 420
 421                         /* The second CAS must happen after the first CAS or frag->next. */
 422                         mono_memory_write_barrier ();
 423
 424                         /* Fail if the previous node was deleted and its CAS wins */
 425                         if (InterlockedCompareExchangePointer ((volatile gpointer*)prev_ptr, unmask (next), frag) != frag) {
 426                                 prev_ptr = find_previous_pointer_fragment (allocator, frag);
 427                                 continue;
 428                         }
 429                         break;
 430                 }
 431         }
 432
 433         return p;
 434 }
 435
 436 static void*
 437 serial_alloc_from_fragment (SgenFragment **previous, SgenFragment *frag, size_t size)
 438 {
 439         char *p = frag->fragment_next;
 440         char *end = p + size;
 441
 442         if (end > frag->fragment_end)
 443                 return NULL;
 444
 445         frag->fragment_next = end;
 446
 447         if (frag->fragment_end - end < SGEN_MAX_NURSERY_WASTE) {
 448                 *previous = frag->next;
 449
 450                 /* Clear the remaining space, pinning depends on this. FIXME move this to use phony arrays */
 451                 memset (end, 0, frag->fragment_end - end);
 452
 453                 *previous = frag->next;
 454         }
 455
 456         return p;
 457 }
 458
 459 void*
 460 sgen_fragment_allocator_par_alloc (SgenFragmentAllocator *allocator, size_t size)
 461 {
 462         SgenFragment *frag;
 463
 464 #ifdef NALLOC_DEBUG
 465         InterlockedIncrement (&alloc_count);
 466 #endif
 467
 468 restart:
 469         for (frag = unmask (allocator->alloc_head); unmask (frag); frag = unmask (frag->next)) {
 470                 HEAVY_STAT (InterlockedIncrement (&stat_alloc_iterations));
 471
 472                 if (size <= (size_t)(frag->fragment_end - frag->fragment_next)) {
 473                         void *p = par_alloc_from_fragment (allocator, frag, size);
 474                         if (!p) {
 475                                 HEAVY_STAT (InterlockedIncrement (&stat_alloc_retries));
 476                                 goto restart;
 477                         }
 478 #ifdef NALLOC_DEBUG
 479                         add_alloc_record (p, size, FIXED_ALLOC);
 480 #endif
 481                         return p;
 482                 }
 483         }
 484         return NULL;
 485 }
 486
 487 void*
 488 sgen_fragment_allocator_serial_alloc (SgenFragmentAllocator *allocator, size_t size)
 489 {
 490         SgenFragment *frag;
 491         SgenFragment **previous;
 492 #ifdef NALLOC_DEBUG
 493         InterlockedIncrement (&alloc_count);
 494 #endif
 495
 496         previous = &allocator->alloc_head;
 497
 498         for (frag = *previous; frag; frag = *previous) {
 499                 char *p = serial_alloc_from_fragment (previous, frag, size);
 500
 501                 HEAVY_STAT (InterlockedIncrement (&stat_alloc_iterations));
 502
 503                 if (p) {
 504 #ifdef NALLOC_DEBUG
 505                         add_alloc_record (p, size, FIXED_ALLOC);
 506 #endif
 507                         return p;
 508                 }
 509                 previous = &frag->next;
 510         }
 511         return NULL;
 512 }
 513
 514 void*
 515 sgen_fragment_allocator_serial_range_alloc (SgenFragmentAllocator *allocator, size_t desired_size, size_t minimum_size, size_t *out_alloc_size)
 516 {
 517         SgenFragment *frag, **previous, *min_frag = NULL, **prev_min_frag = NULL;
 518         size_t current_minimum = minimum_size;
 519
 520 #ifdef NALLOC_DEBUG
 521         InterlockedIncrement (&alloc_count);
 522 #endif
 523
 524         previous = &allocator->alloc_head;
 525
 526         for (frag = *previous; frag; frag = *previous) {
 527                 size_t frag_size = frag->fragment_end - frag->fragment_next;
 528
 529                 HEAVY_STAT (InterlockedIncrement (&stat_alloc_range_iterations));
 530
 531                 if (desired_size <= frag_size) {
 532                         void *p;
 533                         *out_alloc_size = desired_size;
 534
 535                         p = serial_alloc_from_fragment (previous, frag, desired_size);
 536 #ifdef NALLOC_DEBUG
 537                         add_alloc_record (p, desired_size, RANGE_ALLOC);
 538 #endif
 539                         return p;
 540                 }
 541                 if (current_minimum <= frag_size) {
 542                         min_frag = frag;
 543                         prev_min_frag = previous;
 544                         current_minimum = frag_size;
 545                 }
 546                 previous = &frag->next;
 547         }
 548
 549         if (min_frag) {
 550                 void *p;
 551                 size_t frag_size = min_frag->fragment_end - min_frag->fragment_next;
 552                 *out_alloc_size = frag_size;
 553
 554                 p = serial_alloc_from_fragment (prev_min_frag, min_frag, frag_size);
 555
 556 #ifdef NALLOC_DEBUG
 557                 add_alloc_record (p, frag_size, RANGE_ALLOC);
 558 #endif
 559                 return p;
 560         }
 561
 562         return NULL;
 563 }
 564
 565 void*
 566 sgen_fragment_allocator_par_range_alloc (SgenFragmentAllocator *allocator, size_t desired_size, size_t minimum_size, size_t *out_alloc_size)
 567 {
 568         SgenFragment *frag, *min_frag;
 569         size_t current_minimum;
 570
 571 restart:
 572         min_frag = NULL;
 573         current_minimum = minimum_size;
 574
 575 #ifdef NALLOC_DEBUG
 576         InterlockedIncrement (&alloc_count);
 577 #endif
 578
 579         for (frag = unmask (allocator->alloc_head); frag; frag = unmask (frag->next)) {
 580                 size_t frag_size = frag->fragment_end - frag->fragment_next;
 581
 582                 HEAVY_STAT (InterlockedIncrement (&stat_alloc_range_iterations));
 583
 584                 if (desired_size <= frag_size) {
 585                         void *p;
 586                         *out_alloc_size = desired_size;
 587
 588                         p = par_alloc_from_fragment (allocator, frag, desired_size);
 589                         if (!p) {
 590                                 HEAVY_STAT (InterlockedIncrement (&stat_alloc_range_retries));
 591                                 goto restart;
 592                         }
 593 #ifdef NALLOC_DEBUG
 594                         add_alloc_record (p, desired_size, RANGE_ALLOC);
 595 #endif
 596                         return p;
 597                 }
 598                 if (current_minimum <= frag_size) {
 599                         min_frag = frag;
 600                         current_minimum = frag_size;
 601                 }
 602         }
 603
 604         /* The second fragment_next read should be ordered in respect to the first code block */
 605         mono_memory_barrier ();
 606
 607         if (min_frag) {
 608                 void *p;
 609                 size_t frag_size;
 610
 611                 frag_size = min_frag->fragment_end - min_frag->fragment_next;
 612                 if (frag_size < minimum_size)
 613                         goto restart;
 614
 615                 *out_alloc_size = frag_size;
 616
 617                 mono_memory_barrier ();
 618                 p = par_alloc_from_fragment (allocator, min_frag, frag_size);
 619
 620                 /*XXX restarting here is quite dubious given this is already second chance allocation. */
 621                 if (!p) {
 622                         HEAVY_STAT (InterlockedIncrement (&stat_alloc_retries));
 623                         goto restart;
 624                 }
 625 #ifdef NALLOC_DEBUG
 626                 add_alloc_record (p, frag_size, RANGE_ALLOC);
 627 #endif
 628                 return p;
 629         }
 630
 631         return NULL;
 632 }
 633
 634 void
 635 sgen_clear_allocator_fragments (SgenFragmentAllocator *allocator)
 636 {
 637         SgenFragment *frag;
 638
 639         for (frag = unmask (allocator->alloc_head); frag; frag = unmask (frag->next)) {
 640                 SGEN_LOG (4, "Clear nursery frag %p-%p", frag->fragment_next, frag->fragment_end);
 641                 sgen_clear_range (frag->fragment_next, frag->fragment_end);
 642 #ifdef NALLOC_DEBUG
 643                 add_alloc_record (frag->fragment_next, frag->fragment_end - frag->fragment_next, CLEAR_NURSERY_FRAGS);
 644 #endif
 645         }
 646 }
 647
 648 /* Clear all remaining nursery fragments */
 649 void
 650 sgen_clear_nursery_fragments (void)
 651 {
 652         if (sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION || sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION_DEBUG) {
 653                 sgen_clear_allocator_fragments (&mutator_allocator);
 654                 sgen_minor_collector.clear_fragments ();
 655         }
 656 }
 657
 658 /*
 659  * Mark a given range of memory as invalid.
 660  *
 661  * This can be done either by zeroing memory or by placing
 662  * a phony byte[] array. This keeps the heap forward walkable.
 663  *
 664  * This function ignores calls with a zero range, even if
 665  * both start and end are NULL.
 666  */
 667 void
 668 sgen_clear_range (char *start, char *end)
 669 {
 670         MonoArray *o;
 671         size_t size = end - start;
 672
 673         if ((start && !end) || (start > end))
 674                 g_error ("Invalid range [%p %p]", start, end);
 675
 676         if (size < sizeof (MonoArray)) {
 677                 memset (start, 0, size);
 678                 return;
 679         }
 680
 681         o = (MonoArray*)start;
 682         o->obj.vtable = sgen_get_array_fill_vtable ();
 683         /* Mark this as not a real object */
 684         o->obj.synchronisation = GINT_TO_POINTER (-1);
 685         o->bounds = NULL;
 686         o->max_length = (mono_array_size_t)(size - sizeof (MonoArray));
 687         sgen_set_nursery_scan_start (start);
 688         g_assert (start + sgen_safe_object_get_size ((MonoObject*)o) == end);
 689 }
 690
 691 void
 692 sgen_nursery_allocator_prepare_for_pinning (void)
 693 {
 694         sgen_clear_allocator_fragments (&mutator_allocator);
 695         sgen_minor_collector.clear_fragments ();
 696 }
 697
 698 static mword fragment_total = 0;
 699 /*
 700  * We found a fragment of free memory in the nursery: memzero it and if
 701  * it is big enough, add it to the list of fragments that can be used for
 702  * allocation.
 703  */
 704 static void
 705 add_nursery_frag (SgenFragmentAllocator *allocator, size_t frag_size, char* frag_start, char* frag_end)
 706 {
 707         SGEN_LOG (4, "Found empty fragment: %p-%p, size: %zd", frag_start, frag_end, frag_size);
 708         binary_protocol_empty (frag_start, frag_size);
 709         MONO_GC_NURSERY_SWEPT ((mword)frag_start, frag_end - frag_start);
 710         /* Not worth dealing with smaller fragments: need to tune */
 711         if (frag_size >= SGEN_MAX_NURSERY_WASTE) {
 712                 /* memsetting just the first chunk start is bound to provide better cache locality */
 713                 if (sgen_get_nursery_clear_policy () == CLEAR_AT_GC)
 714                         memset (frag_start, 0, frag_size);
 715                 else if (sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION_DEBUG)
 716                         memset (frag_start, 0xff, frag_size);
 717
 718 #ifdef NALLOC_DEBUG
 719                 /* XXX convert this into a flight record entry
 720                 printf ("\tfragment [%p %p] size %zd\n", frag_start, frag_end, frag_size);
 721                 */
 722 #endif
 723                 sgen_fragment_allocator_add (allocator, frag_start, frag_end);
 724                 fragment_total += frag_size;
 725         } else {
 726                 /* Clear unused fragments, pinning depends on this */
 727                 sgen_clear_range (frag_start, frag_end);
 728                 HEAVY_STAT (InterlockedExchangeAdd (&stat_wasted_bytes_small_areas, frag_size));
 729         }
 730 }
 731
 732 static void
 733 fragment_list_reverse (SgenFragmentAllocator *allocator)
 734 {
 735         SgenFragment *prev = NULL, *list = allocator->region_head;
 736         while (list) {
 737                 SgenFragment *next = list->next;
 738                 list->next = prev;
 739                 list->next_in_order = prev;
 740                 prev = list;
 741                 list = next;
 742         }
 743
 744         allocator->region_head = allocator->alloc_head = prev;
 745 }
 746
 747 mword
 748 sgen_build_nursery_fragments (GCMemSection *nursery_section, SgenGrayQueue *unpin_queue)
 749 {
 750         char *frag_start, *frag_end;
 751         size_t frag_size;
 752         SgenFragment *frags_ranges;
 753         void **pin_start, **pin_entry, **pin_end;
 754
 755 #ifdef NALLOC_DEBUG
 756         reset_alloc_records ();
 757 #endif
 758         /*The mutator fragments are done. We no longer need them. */
 759         sgen_fragment_allocator_release (&mutator_allocator);
 760
 761         frag_start = sgen_nursery_start;
 762         fragment_total = 0;
 763
 764         /* The current nursery might give us a fragment list to exclude [start, next[*/
 765         frags_ranges = sgen_minor_collector.build_fragments_get_exclude_head ();
 766
 767         /* clear scan starts */
 768         memset (nursery_section->scan_starts, 0, nursery_section->num_scan_start * sizeof (gpointer));
 769
 770         pin_start = pin_entry = sgen_pinning_get_entry (nursery_section->pin_queue_first_entry);
 771         pin_end = sgen_pinning_get_entry (nursery_section->pin_queue_last_entry);
 772
 773         while (pin_entry < pin_end || frags_ranges) {
 774                 char *addr0, *addr1;
 775                 size_t size;
 776
 777                 addr0 = addr1 = sgen_nursery_end;
 778                 if (pin_entry < pin_end)
 779                         addr0 = *pin_entry;
 780                 if (frags_ranges)
 781                         addr1 = frags_ranges->fragment_start;
 782
 783                 if (addr0 < addr1) {
 784                         if (unpin_queue)
 785                                 GRAY_OBJECT_ENQUEUE (unpin_queue, addr0, sgen_obj_get_descriptor_safe (addr0));
 786                         else
 787                                 SGEN_UNPIN_OBJECT (addr0);
 788                         size = SGEN_ALIGN_UP (sgen_safe_object_get_size ((MonoObject*)addr0));
 789                         CANARIFY_SIZE (size);
 790                         sgen_set_nursery_scan_start (addr0);
 791                         frag_end = addr0;
 792                         ++pin_entry;
 793                 } else {
 794                         frag_end = addr1;
 795                         size = frags_ranges->fragment_next - addr1;
 796                         frags_ranges = frags_ranges->next_in_order;
 797                 }
 798
 799                 frag_size = frag_end - frag_start;
 800
 801                 if (size == 0)
 802                         continue;
 803
 804                 g_assert (frag_size >= 0);
 805                 g_assert (size > 0);
 806                 if (frag_size && size)
 807                         add_nursery_frag (&mutator_allocator, frag_size, frag_start, frag_end);
 808
 809                 frag_size = size;
 810 #ifdef NALLOC_DEBUG
 811                 add_alloc_record (*pin_entry, frag_size, PINNING);
 812 #endif
 813                 frag_start = frag_end + frag_size;
 814         }
 815
 816         nursery_last_pinned_end = frag_start;
 817         frag_end = sgen_nursery_end;
 818         frag_size = frag_end - frag_start;
 819         if (frag_size)
 820                 add_nursery_frag (&mutator_allocator, frag_size, frag_start, frag_end);
 821
 822         /* Now it's safe to release the fragments exclude list. */
 823         sgen_minor_collector.build_fragments_release_exclude_head ();
 824
 825         /* First we reorder the fragment list to be in ascending address order. This makes H/W prefetchers happier. */
 826         fragment_list_reverse (&mutator_allocator);
 827
 828         /*The collector might want to do something with the final nursery fragment list.*/
 829         sgen_minor_collector.build_fragments_finish (&mutator_allocator);
 830
 831         if (!unmask (mutator_allocator.alloc_head)) {
 832                 SGEN_LOG (1, "Nursery fully pinned");
 833                 for (pin_entry = pin_start; pin_entry < pin_end; ++pin_entry) {
 834                         void *p = *pin_entry;
 835                         SGEN_LOG (3, "Bastard pinning obj %p (%s), size: %zd", p, sgen_safe_name (p), sgen_safe_object_get_size (p));
 836                 }
 837         }
 838         return fragment_total;
 839 }
 840
 841 char *
 842 sgen_nursery_alloc_get_upper_alloc_bound (void)
 843 {
 844         /*FIXME we need to calculate the collector upper bound as well, but this must be done in the previous GC. */
 845         return sgen_nursery_end;
 846 }
 847
 848 /*** Nursery memory allocation ***/
 849 void
 850 sgen_nursery_retire_region (void *address, ptrdiff_t size)
 851 {
 852         HEAVY_STAT (InterlockedExchangeAdd (&stat_wasted_bytes_discarded_fragments, size));
 853 }
 854
 855 gboolean
 856 sgen_can_alloc_size (size_t size)
 857 {
 858         SgenFragment *frag;
 859
 860         if (!SGEN_CAN_ALIGN_UP (size))
 861                 return FALSE;
 862
 863         size = SGEN_ALIGN_UP (size);
 864
 865         for (frag = unmask (mutator_allocator.alloc_head); frag; frag = unmask (frag->next)) {
 866                 if ((size_t)(frag->fragment_end - frag->fragment_next) >= size)
 867                         return TRUE;
 868         }
 869         return FALSE;
 870 }
 871
 872 void*
 873 sgen_nursery_alloc (size_t size)
 874 {
 875         SGEN_ASSERT (1, size >= sizeof (MonoObject) && size <= (SGEN_MAX_SMALL_OBJ_SIZE + CANARY_SIZE), "Invalid nursery object size");
 876
 877         SGEN_LOG (4, "Searching nursery for size: %zd", size);
 878         size = SGEN_ALIGN_UP (size);
 879
 880         HEAVY_STAT (InterlockedIncrement (&stat_nursery_alloc_requests));
 881
 882         return sgen_fragment_allocator_par_alloc (&mutator_allocator, size);
 883 }
 884
 885 void*
 886 sgen_nursery_alloc_range (size_t desired_size, size_t minimum_size, size_t *out_alloc_size)
 887 {
 888         SGEN_LOG (4, "Searching for byte range desired size: %zd minimum size %zd", desired_size, minimum_size);
 889
 890         HEAVY_STAT (InterlockedIncrement (&stat_nursery_alloc_range_requests));
 891
 892         return sgen_fragment_allocator_par_range_alloc (&mutator_allocator, desired_size, minimum_size, out_alloc_size);
 893 }
 894
 895 /*** Initialization ***/
 896
 897 #ifdef HEAVY_STATISTICS
 898
 899 void
 900 sgen_nursery_allocator_init_heavy_stats (void)
 901 {
 902         mono_counters_register ("bytes wasted trailer fragments", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_wasted_bytes_trailer);
 903         mono_counters_register ("bytes wasted small areas", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_wasted_bytes_small_areas);
 904         mono_counters_register ("bytes wasted discarded fragments", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_wasted_bytes_discarded_fragments);
 905
 906         mono_counters_register ("# nursery alloc requests", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_nursery_alloc_requests);
 907         mono_counters_register ("# nursery alloc iterations", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_alloc_iterations);
 908         mono_counters_register ("# nursery alloc retries", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_alloc_retries);
 909
 910         mono_counters_register ("# nursery alloc range requests", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_nursery_alloc_range_requests);
 911         mono_counters_register ("# nursery alloc range iterations", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_alloc_range_iterations);
 912         mono_counters_register ("# nursery alloc range restries", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_alloc_range_retries);
 913 }
 914
 915 #endif
 916
 917 void
 918 sgen_init_nursery_allocator (void)
 919 {
 920         sgen_register_fixed_internal_mem_type (INTERNAL_MEM_FRAGMENT, sizeof (SgenFragment));
 921 #ifdef NALLOC_DEBUG
 922         alloc_records = sgen_alloc_os_memory (sizeof (AllocRecord) * ALLOC_RECORD_COUNT, SGEN_ALLOC_INTERNAL | SGEN_ALLOC_ACTIVATE, "debugging memory");
 923 #endif
 924 }
 925
 926 void
 927 sgen_nursery_alloc_prepare_for_minor (void)
 928 {
 929         sgen_minor_collector.prepare_to_space (sgen_space_bitmap, sgen_space_bitmap_size);
 930 }
 931
 932 void
 933 sgen_nursery_alloc_prepare_for_major (void)
 934 {
 935         sgen_minor_collector.prepare_to_space (sgen_space_bitmap, sgen_space_bitmap_size);
 936 }
 937
 938 void
 939 sgen_nursery_allocator_set_nursery_bounds (char *start, char *end)
 940 {
 941         sgen_nursery_start = start;
 942         sgen_nursery_end = end;
 943
 944         /*
 945          * This will not divide evenly for tiny nurseries (<4kb), so we make sure to be on
 946          * the right side of things and round up.  We could just do a MIN(1,x) instead,
 947          * since the nursery size must be a power of 2.
 948          */
 949         sgen_space_bitmap_size = (end - start + SGEN_TO_SPACE_GRANULE_IN_BYTES * 8 - 1) / (SGEN_TO_SPACE_GRANULE_IN_BYTES * 8);
 950         sgen_space_bitmap = g_malloc0 (sgen_space_bitmap_size);
 951
 952         /* Setup the single first large fragment */
 953         sgen_minor_collector.init_nursery (&mutator_allocator, start, end);
 954 }
 955
 956 #endif