mono/sgen/sgen-nursery-allocator.c

   1 /**
   2  * \file
   3  * Nursery allocation code.
   4  *
   5  * Copyright 2009-2010 Novell, Inc.
   6  *           2011 Rodrigo Kumpera
   7  *
   8  * Copyright 2011 Xamarin Inc  (http://www.xamarin.com)
   9  * Copyright (C) 2012 Xamarin Inc
  10  *
  11  * Licensed under the MIT license. See LICENSE file in the project root for full license information.
  12  */
  13
  14 /*
  15  * The young generation is divided into fragments. This is because
  16  * we can hand one fragments to a thread for lock-less fast alloc and
  17  * because the young generation ends up fragmented anyway by pinned objects.
  18  * Once a collection is done, a list of fragments is created. When doing
  19  * thread local alloc we use smallish nurseries so we allow new threads to
  20  * allocate memory from gen0 without triggering a collection. Threads that
  21  * are found to allocate lots of memory are given bigger fragments. This
  22  * should make the finalizer thread use little nursery memory after a while.
  23  * We should start assigning threads very small fragments: if there are many
  24  * threads the nursery will be full of reserved space that the threads may not
  25  * use at all, slowing down allocation speed.
  26  * Thread local allocation is done from areas of memory Hotspot calls Thread Local
  27  * Allocation Buffers (TLABs).
  28  */
  29 #include "config.h"
  30 #ifdef HAVE_SGEN_GC
  31
  32 #ifdef HAVE_UNISTD_H
  33 #include <unistd.h>
  34 #endif
  35 #ifdef HAVE_PTHREAD_H
  36 #include <pthread.h>
  37 #endif
  38 #ifdef HAVE_SEMAPHORE_H
  39 #include <semaphore.h>
  40 #endif
  41 #include <stdio.h>
  42 #include <string.h>
  43 #include <errno.h>
  44 #include <assert.h>
  45 #ifdef __MACH__
  46 #undef _XOPEN_SOURCE
  47 #endif
  48 #ifdef __MACH__
  49 #define _XOPEN_SOURCE
  50 #endif
  51
  52 #include "mono/sgen/sgen-gc.h"
  53 #include "mono/sgen/sgen-cardtable.h"
  54 #include "mono/sgen/sgen-protocol.h"
  55 #include "mono/sgen/sgen-memory-governor.h"
  56 #include "mono/sgen/sgen-pinning.h"
  57 #include "mono/sgen/sgen-client.h"
  58 #include "mono/utils/mono-membar.h"
  59
  60 /* Enable it so nursery allocation diagnostic data is collected */
  61 //#define NALLOC_DEBUG 1
  62
  63 /* The mutator allocs from here. */
  64 static SgenFragmentAllocator mutator_allocator;
  65
  66 /* freeelist of fragment structures */
  67 static SgenFragment *fragment_freelist = NULL;
  68
  69 char *sgen_nursery_start;
  70 char *sgen_nursery_end;
  71
  72 /* good sizes are 512KB-1MB: larger ones increase a lot memzeroing time */
  73 size_t sgen_nursery_size;
  74 /*
  75  * Maximum size that we can resize the nursery to.
  76  * If sgen_nursery_default_size == sgen_nursery_max_size then we are not
  77  * dynamically resizing the nursery
  78  */
  79 size_t sgen_nursery_max_size;
  80 size_t sgen_nursery_min_size;
  81 /* The number of trailing 0 bits in sgen_nursery_max_size */
  82 int sgen_nursery_bits;
  83
  84
  85 char *sgen_space_bitmap;
  86 size_t sgen_space_bitmap_size;
  87
  88 #ifdef HEAVY_STATISTICS
  89
  90 static mword stat_wasted_bytes_trailer = 0;
  91 static mword stat_wasted_bytes_small_areas = 0;
  92 static mword stat_wasted_bytes_discarded_fragments = 0;
  93 static guint64 stat_nursery_alloc_requests = 0;
  94 static guint64 stat_alloc_iterations = 0;
  95 static guint64 stat_alloc_retries = 0;
  96
  97 static guint64 stat_nursery_alloc_range_requests = 0;
  98 static guint64 stat_alloc_range_iterations = 0;
  99 static guint64 stat_alloc_range_retries = 0;
 100
 101 #endif
 102
 103 /************************************Nursery allocation debugging *********************************************/
 104
 105 #ifdef NALLOC_DEBUG
 106
 107 enum {
 108         FIXED_ALLOC = 1,
 109         RANGE_ALLOC,
 110         PINNING,
 111         BLOCK_ZEROING,
 112         CLEAR_NURSERY_FRAGS
 113 };
 114
 115 typedef struct {
 116         char *address;
 117         size_t size;
 118         int reason;
 119         int seq;
 120         MonoNativeThreadId tid;
 121 } AllocRecord;
 122
 123 #define ALLOC_RECORD_COUNT 128000
 124
 125
 126 static AllocRecord *alloc_records;
 127 static volatile int next_record;
 128 static volatile int alloc_count;
 129
 130 void dump_alloc_records (void);
 131 void verify_alloc_records (void);
 132
 133 static const char*
 134 get_reason_name (AllocRecord *rec)
 135 {
 136         switch (rec->reason) {
 137         case FIXED_ALLOC: return "fixed-alloc";
 138         case RANGE_ALLOC: return "range-alloc";
 139         case PINNING: return "pinning";
 140         case BLOCK_ZEROING: return "block-zeroing";
 141         case CLEAR_NURSERY_FRAGS: return "clear-nursery-frag";
 142         default: return "invalid";
 143         }
 144 }
 145
 146 static void
 147 reset_alloc_records (void)
 148 {
 149         next_record = 0;
 150         alloc_count = 0;
 151 }
 152
 153 static void
 154 add_alloc_record (char *addr, size_t size, int reason)
 155 {
 156         int idx = mono_atomic_inc_i32 (&next_record) - 1;
 157         alloc_records [idx].address = addr;
 158         alloc_records [idx].size = size;
 159         alloc_records [idx].reason = reason;
 160         alloc_records [idx].seq = idx;
 161         alloc_records [idx].tid = mono_native_thread_id_get ();
 162 }
 163
 164 static int
 165 comp_alloc_record (const void *_a, const void *_b)
 166 {
 167         const AllocRecord *a = _a;
 168         const AllocRecord *b = _b;
 169         if (a->address == b->address)
 170                 return a->seq - b->seq;
 171         return a->address - b->address;
 172 }
 173
 174 #define rec_end(REC) ((REC)->address + (REC)->size)
 175
 176 void
 177 dump_alloc_records (void)
 178 {
 179         int i;
 180         sgen_qsort (alloc_records, next_record, sizeof (AllocRecord), comp_alloc_record);
 181
 182         printf ("------------------------------------DUMP RECORDS----------------------------\n");
 183         for (i = 0; i < next_record; ++i) {
 184                 AllocRecord *rec = alloc_records + i;
 185                 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);
 186         }
 187 }
 188
 189 void
 190 verify_alloc_records (void)
 191 {
 192         int i;
 193         int total = 0;
 194         int holes = 0;
 195         int max_hole = 0;
 196         AllocRecord *prev = NULL;
 197
 198         sgen_qsort (alloc_records, next_record, sizeof (AllocRecord), comp_alloc_record);
 199         printf ("------------------------------------DUMP RECORDS- %d %d---------------------------\n", next_record, alloc_count);
 200         for (i = 0; i < next_record; ++i) {
 201                 AllocRecord *rec = alloc_records + i;
 202                 int hole_size = 0;
 203                 total += rec->size;
 204                 if (prev) {
 205                         if (rec_end (prev) > rec->address)
 206                                 printf ("WE GOT OVERLAPPING objects %p and %p\n", prev->address, rec->address);
 207                         if ((rec->address - rec_end (prev)) >= 8)
 208                                 ++holes;
 209                         hole_size = rec->address - rec_end (prev);
 210                         max_hole = MAX (max_hole, hole_size);
 211                 }
 212                 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);
 213                 prev = rec;
 214         }
 215         printf ("SUMMARY total alloc'd %d holes %d max_hole %d\n", total, holes, max_hole);
 216 }
 217
 218 #endif
 219
 220 /*********************************************************************************/
 221
 222 static gpointer
 223 mask (gpointer n, uintptr_t bit)
 224 {
 225         return (gpointer)(((uintptr_t)n) | bit);
 226 }
 227
 228 static gpointer
 229 unmask (gpointer p)
 230 {
 231         return (gpointer)((uintptr_t)p & ~(uintptr_t)0x3);
 232 }
 233
 234 static uintptr_t
 235 get_mark (gpointer n)
 236 {
 237         return (uintptr_t)n & 0x1;
 238 }
 239
 240 /*MUST be called with world stopped*/
 241 SgenFragment*
 242 sgen_fragment_allocator_alloc (void)
 243 {
 244         SgenFragment *frag = fragment_freelist;
 245         if (frag) {
 246                 fragment_freelist = frag->next_in_order;
 247                 frag->next = frag->next_in_order = NULL;
 248                 return frag;
 249         }
 250         frag = (SgenFragment *)sgen_alloc_internal (INTERNAL_MEM_FRAGMENT);
 251         frag->next = frag->next_in_order = NULL;
 252         return frag;
 253 }
 254
 255 void
 256 sgen_fragment_allocator_add (SgenFragmentAllocator *allocator, char *start, char *end)
 257 {
 258         SgenFragment *fragment;
 259
 260         fragment = sgen_fragment_allocator_alloc ();
 261         fragment->fragment_start = start;
 262         fragment->fragment_next = start;
 263         fragment->fragment_end = end;
 264         fragment->next_in_order = fragment->next = (SgenFragment *)unmask (allocator->region_head);
 265
 266         allocator->region_head = allocator->alloc_head = fragment;
 267         g_assert (fragment->fragment_end > fragment->fragment_start);
 268 }
 269
 270 void
 271 sgen_fragment_allocator_release (SgenFragmentAllocator *allocator)
 272 {
 273         SgenFragment *last = allocator->region_head;
 274         if (!last)
 275                 return;
 276
 277         /* Find the last fragment in insert order */
 278         for (; last->next_in_order; last = last->next_in_order) ;
 279
 280         last->next_in_order = fragment_freelist;
 281         fragment_freelist = allocator->region_head;
 282         allocator->alloc_head = allocator->region_head = NULL;
 283 }
 284
 285 static SgenFragment**
 286 find_previous_pointer_fragment (SgenFragmentAllocator *allocator, SgenFragment *frag)
 287 {
 288         SgenFragment **prev;
 289         SgenFragment *cur, *next;
 290 #ifdef NALLOC_DEBUG
 291         int count = 0;
 292 #endif
 293
 294 try_again:
 295         prev = &allocator->alloc_head;
 296 #ifdef NALLOC_DEBUG
 297         if (count++ > 5)
 298                 printf ("retry count for fppf is %d\n", count);
 299 #endif
 300
 301         cur = (SgenFragment *)unmask (*prev);
 302
 303         while (1) {
 304                 if (cur == NULL)
 305                         return NULL;
 306                 next = cur->next;
 307
 308                 /*
 309                  * We need to make sure that we dereference prev below
 310                  * after reading cur->next above, so we need a read
 311                  * barrier.
 312                  */
 313                 mono_memory_read_barrier ();
 314
 315                 if (*prev != cur)
 316                         goto try_again;
 317
 318                 if (!get_mark (next)) {
 319                         if (cur == frag)
 320                                 return prev;
 321                         prev = &cur->next;
 322                 } else {
 323                         next = (SgenFragment *)unmask (next);
 324                         if (mono_atomic_cas_ptr ((volatile gpointer*)prev, next, cur) != cur)
 325                                 goto try_again;
 326                         /*we must make sure that the next from cur->next happens after*/
 327                         mono_memory_write_barrier ();
 328                 }
 329
 330                 cur = (SgenFragment *)unmask (next);
 331         }
 332         return NULL;
 333 }
 334
 335 static gboolean
 336 claim_remaining_size (SgenFragment *frag, char *alloc_end)
 337 {
 338         /* All space used, nothing to claim. */
 339         if (frag->fragment_end <= alloc_end)
 340                 return FALSE;
 341
 342         /* Try to alloc all the remaining space. */
 343         return mono_atomic_cas_ptr ((volatile gpointer*)&frag->fragment_next, frag->fragment_end, alloc_end) == alloc_end;
 344 }
 345
 346 static void*
 347 par_alloc_from_fragment (SgenFragmentAllocator *allocator, SgenFragment *frag, size_t size)
 348 {
 349         char *p = frag->fragment_next;
 350         char *end = p + size;
 351
 352         if (end > frag->fragment_end || end > (sgen_nursery_start + sgen_nursery_size))
 353                 return NULL;
 354
 355         /* p = frag->fragment_next must happen before */
 356         mono_memory_barrier ();
 357
 358         if (mono_atomic_cas_ptr ((volatile gpointer*)&frag->fragment_next, end, p) != p)
 359                 return NULL;
 360
 361         if (frag->fragment_end - end < SGEN_MAX_NURSERY_WASTE) {
 362                 SgenFragment *next, **prev_ptr;
 363
 364                 /*
 365                  * Before we clean the remaining nursery, we must claim the remaining space
 366                  * as it could end up been used by the range allocator since it can end up
 367                  * allocating from this dying fragment as it doesn't respect SGEN_MAX_NURSERY_WASTE
 368                  * when doing second chance allocation.
 369                  */
 370                 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)) {
 371                         sgen_clear_range (end, frag->fragment_end);
 372                         HEAVY_STAT (stat_wasted_bytes_trailer += frag->fragment_end - end);
 373 #ifdef NALLOC_DEBUG
 374                         add_alloc_record (end, frag->fragment_end - end, BLOCK_ZEROING);
 375 #endif
 376                 }
 377
 378                 prev_ptr = find_previous_pointer_fragment (allocator, frag);
 379
 380                 /*Use Michaels linked list remove*/
 381
 382                 /*prev_ptr will be null if the fragment was removed concurrently */
 383                 while (prev_ptr) {
 384                         next = frag->next;
 385
 386                         /*already deleted*/
 387                         if (!get_mark (next)) {
 388                                 /*frag->next read must happen before the first CAS*/
 389                                 mono_memory_write_barrier ();
 390
 391                                 /*Fail if the next node is removed concurrently and its CAS wins */
 392                                 if (mono_atomic_cas_ptr ((volatile gpointer*)&frag->next, mask (next, 1), next) != next) {
 393                                         continue;
 394                                 }
 395                         }
 396
 397                         /* The second CAS must happen after the first CAS or frag->next. */
 398                         mono_memory_write_barrier ();
 399
 400                         /* Fail if the previous node was deleted and its CAS wins */
 401                         if (mono_atomic_cas_ptr ((volatile gpointer*)prev_ptr, unmask (next), frag) != frag) {
 402                                 prev_ptr = find_previous_pointer_fragment (allocator, frag);
 403                                 continue;
 404                         }
 405                         break;
 406                 }
 407         }
 408
 409         return p;
 410 }
 411
 412 static void*
 413 serial_alloc_from_fragment (SgenFragment **previous, SgenFragment *frag, size_t size)
 414 {
 415         char *p = frag->fragment_next;
 416         char *end = p + size;
 417
 418         if (end > frag->fragment_end)
 419                 return NULL;
 420
 421         frag->fragment_next = end;
 422
 423         if (frag->fragment_end - end < SGEN_MAX_NURSERY_WASTE) {
 424                 *previous = frag->next;
 425
 426                 /* Clear the remaining space, pinning depends on this. FIXME move this to use phony arrays */
 427                 memset (end, 0, frag->fragment_end - end);
 428
 429                 *previous = frag->next;
 430         }
 431
 432         return p;
 433 }
 434
 435 void*
 436 sgen_fragment_allocator_par_alloc (SgenFragmentAllocator *allocator, size_t size)
 437 {
 438         SgenFragment *frag;
 439
 440 #ifdef NALLOC_DEBUG
 441         mono_atomic_inc_i32 (&alloc_count);
 442 #endif
 443
 444 restart:
 445         for (frag = (SgenFragment *)unmask (allocator->alloc_head); unmask (frag); frag = (SgenFragment *)unmask (frag->next)) {
 446                 size_t frag_size = frag->fragment_end - frag->fragment_next;
 447
 448                 if (frag->fragment_next >= (sgen_nursery_start + sgen_nursery_size))
 449                         continue;
 450
 451                 HEAVY_STAT (++stat_alloc_iterations);
 452
 453                 if (size <= frag_size) {
 454                         void *p = par_alloc_from_fragment (allocator, frag, size);
 455                         if (!p) {
 456                                 HEAVY_STAT (++stat_alloc_retries);
 457                                 goto restart;
 458                         }
 459 #ifdef NALLOC_DEBUG
 460                         add_alloc_record (p, size, FIXED_ALLOC);
 461 #endif
 462                         return p;
 463                 }
 464         }
 465         return NULL;
 466 }
 467
 468 void*
 469 sgen_fragment_allocator_serial_range_alloc (SgenFragmentAllocator *allocator, size_t desired_size, size_t minimum_size, size_t *out_alloc_size)
 470 {
 471         SgenFragment *frag, **previous, *min_frag = NULL, **prev_min_frag = NULL;
 472         size_t current_minimum = minimum_size;
 473
 474 #ifdef NALLOC_DEBUG
 475         mono_atomic_inc_i32 (&alloc_count);
 476 #endif
 477
 478         previous = &allocator->alloc_head;
 479
 480         for (frag = *previous; frag; frag = *previous) {
 481                 size_t frag_size = frag->fragment_end - frag->fragment_next;
 482
 483                 HEAVY_STAT (++stat_alloc_range_iterations);
 484
 485                 if (desired_size <= frag_size) {
 486                         void *p;
 487                         *out_alloc_size = desired_size;
 488
 489                         p = serial_alloc_from_fragment (previous, frag, desired_size);
 490 #ifdef NALLOC_DEBUG
 491                         add_alloc_record (p, desired_size, RANGE_ALLOC);
 492 #endif
 493                         return p;
 494                 }
 495                 if (current_minimum <= frag_size) {
 496                         min_frag = frag;
 497                         prev_min_frag = previous;
 498                         current_minimum = frag_size;
 499                 }
 500                 previous = &frag->next;
 501         }
 502
 503         if (min_frag) {
 504                 void *p;
 505                 size_t frag_size = min_frag->fragment_end - min_frag->fragment_next;
 506                 *out_alloc_size = frag_size;
 507
 508                 p = serial_alloc_from_fragment (prev_min_frag, min_frag, frag_size);
 509
 510 #ifdef NALLOC_DEBUG
 511                 add_alloc_record (p, frag_size, RANGE_ALLOC);
 512 #endif
 513                 return p;
 514         }
 515
 516         return NULL;
 517 }
 518
 519 void*
 520 sgen_fragment_allocator_par_range_alloc (SgenFragmentAllocator *allocator, size_t desired_size, size_t minimum_size, size_t *out_alloc_size)
 521 {
 522         SgenFragment *frag, *min_frag;
 523         size_t current_minimum;
 524
 525 restart:
 526         min_frag = NULL;
 527         current_minimum = minimum_size;
 528
 529 #ifdef NALLOC_DEBUG
 530         mono_atomic_inc_i32 (&alloc_count);
 531 #endif
 532
 533         for (frag = (SgenFragment *)unmask (allocator->alloc_head); frag; frag = (SgenFragment *)unmask (frag->next)) {
 534                 size_t frag_size = frag->fragment_end - frag->fragment_next;
 535
 536                 if (frag->fragment_next >= (sgen_nursery_start + sgen_nursery_size))
 537                         continue;
 538
 539                 HEAVY_STAT (++stat_alloc_range_iterations);
 540
 541                 if (desired_size <= frag_size) {
 542                         void *p;
 543                         *out_alloc_size = desired_size;
 544
 545                         p = par_alloc_from_fragment (allocator, frag, desired_size);
 546                         if (!p) {
 547                                 HEAVY_STAT (++stat_alloc_range_retries);
 548                                 goto restart;
 549                         }
 550 #ifdef NALLOC_DEBUG
 551                         add_alloc_record (p, desired_size, RANGE_ALLOC);
 552 #endif
 553                         return p;
 554                 }
 555                 if (current_minimum <= frag_size) {
 556                         min_frag = frag;
 557                         current_minimum = frag_size;
 558                 }
 559         }
 560
 561         /* The second fragment_next read should be ordered in respect to the first code block */
 562         mono_memory_barrier ();
 563
 564         if (min_frag) {
 565                 void *p;
 566                 size_t frag_size = min_frag->fragment_end - min_frag->fragment_next;
 567
 568                 if (frag_size < minimum_size)
 569                         goto restart;
 570
 571                 *out_alloc_size = frag_size;
 572
 573                 mono_memory_barrier ();
 574                 p = par_alloc_from_fragment (allocator, min_frag, frag_size);
 575
 576                 /*XXX restarting here is quite dubious given this is already second chance allocation. */
 577                 if (!p) {
 578                         HEAVY_STAT (++stat_alloc_retries);
 579                         goto restart;
 580                 }
 581 #ifdef NALLOC_DEBUG
 582                 add_alloc_record (p, frag_size, RANGE_ALLOC);
 583 #endif
 584                 return p;
 585         }
 586
 587         return NULL;
 588 }
 589
 590 void
 591 sgen_clear_allocator_fragments (SgenFragmentAllocator *allocator)
 592 {
 593         SgenFragment *frag;
 594
 595         for (frag = (SgenFragment *)unmask (allocator->alloc_head); frag; frag = (SgenFragment *)unmask (frag->next)) {
 596                 SGEN_LOG (4, "Clear nursery frag %p-%p", frag->fragment_next, frag->fragment_end);
 597                 sgen_clear_range (frag->fragment_next, frag->fragment_end);
 598 #ifdef NALLOC_DEBUG
 599                 add_alloc_record (frag->fragment_next, frag->fragment_end - frag->fragment_next, CLEAR_NURSERY_FRAGS);
 600 #endif
 601         }
 602 }
 603
 604 /* Clear all remaining nursery fragments */
 605 void
 606 sgen_clear_nursery_fragments (void)
 607 {
 608         if (sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION || sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION_DEBUG) {
 609                 sgen_clear_allocator_fragments (&mutator_allocator);
 610                 sgen_minor_collector.clear_fragments ();
 611         }
 612 }
 613
 614 /*
 615  * Mark a given range of memory as invalid.
 616  *
 617  * This can be done either by zeroing memory or by placing
 618  * a phony byte[] array. This keeps the heap forward walkable.
 619  *
 620  * This function ignores calls with a zero range, even if
 621  * both start and end are NULL.
 622  */
 623 void
 624 sgen_clear_range (char *start, char *end)
 625 {
 626         size_t size = end - start;
 627
 628         if ((start && !end) || (start > end))
 629                 g_error ("Invalid range [%p %p]", start, end);
 630
 631         if (sgen_client_array_fill_range (start, size)) {
 632                 sgen_set_nursery_scan_start (start);
 633                 SGEN_ASSERT (0, start + sgen_safe_object_get_size ((GCObject*)start) == end, "Array fill produced wrong size");
 634         }
 635 }
 636
 637 void
 638 sgen_nursery_allocator_prepare_for_pinning (void)
 639 {
 640         sgen_clear_allocator_fragments (&mutator_allocator);
 641         sgen_minor_collector.clear_fragments ();
 642 }
 643
 644 static mword fragment_total = 0;
 645 /*
 646  * We found a fragment of free memory in the nursery: memzero it and if
 647  * it is big enough, add it to the list of fragments that can be used for
 648  * allocation.
 649  */
 650 static void
 651 add_nursery_frag (SgenFragmentAllocator *allocator, size_t frag_size, char* frag_start, char* frag_end)
 652 {
 653         SGEN_LOG (4, "Found empty fragment: %p-%p, size: %zd", frag_start, frag_end, frag_size);
 654         sgen_binary_protocol_empty (frag_start, frag_size);
 655         /* Not worth dealing with smaller fragments: need to tune */
 656         if (frag_size >= SGEN_MAX_NURSERY_WASTE) {
 657                 /* memsetting just the first chunk start is bound to provide better cache locality */
 658                 if (sgen_get_nursery_clear_policy () == CLEAR_AT_GC)
 659                         memset (frag_start, 0, frag_size);
 660                 else if (sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION_DEBUG)
 661                         memset (frag_start, 0xff, frag_size);
 662
 663 #ifdef NALLOC_DEBUG
 664                 /* XXX convert this into a flight record entry
 665                 printf ("\tfragment [%p %p] size %zd\n", frag_start, frag_end, frag_size);
 666                 */
 667 #endif
 668                 sgen_fragment_allocator_add (allocator, frag_start, frag_end);
 669                 fragment_total += frag_size;
 670         } else {
 671                 /* Clear unused fragments, pinning depends on this */
 672                 sgen_clear_range (frag_start, frag_end);
 673                 HEAVY_STAT (stat_wasted_bytes_small_areas += frag_size);
 674         }
 675 }
 676
 677 static void
 678 fragment_list_reverse (SgenFragmentAllocator *allocator)
 679 {
 680         SgenFragment *prev = NULL, *list = allocator->region_head;
 681         while (list) {
 682                 SgenFragment *next = list->next;
 683                 list->next = prev;
 684                 list->next_in_order = prev;
 685                 prev = list;
 686                 list = next;
 687         }
 688
 689         allocator->region_head = allocator->alloc_head = prev;
 690 }
 691
 692 /*
 693  * We split fragments at the border of the current nursery limit. When we
 694  * allocate from the nursery we only consider fragments that start in the
 695  * current nursery section. We build fragments for the entire nursery in
 696  * order to facilitate scanning it for objects (adding a nursery frag also
 697  * marks a region in the nursery as being free)
 698  */
 699 static void
 700 add_nursery_frag_checks (SgenFragmentAllocator *allocator, char *frag_start, char *frag_end)
 701 {
 702         char *nursery_limit = sgen_nursery_start + sgen_nursery_size;
 703
 704         if (frag_start < nursery_limit && frag_end > nursery_limit) {
 705                 add_nursery_frag (allocator, nursery_limit - frag_start, frag_start, nursery_limit);
 706                 add_nursery_frag (allocator, frag_end - nursery_limit, nursery_limit, frag_end);
 707         } else {
 708                 add_nursery_frag (allocator, frag_end - frag_start, frag_start, frag_end);
 709         }
 710 }
 711
 712 mword
 713 sgen_build_nursery_fragments (GCMemSection *nursery_section)
 714 {
 715         char *frag_start, *frag_end;
 716         size_t frag_size;
 717         SgenFragment *frags_ranges;
 718         void **pin_start, **pin_entry, **pin_end;
 719
 720 #ifdef NALLOC_DEBUG
 721         reset_alloc_records ();
 722 #endif
 723         /*The mutator fragments are done. We no longer need them. */
 724         sgen_fragment_allocator_release (&mutator_allocator);
 725
 726         frag_start = sgen_nursery_start;
 727         fragment_total = 0;
 728
 729         /* The current nursery might give us a fragment list to exclude [start, next[*/
 730         frags_ranges = sgen_minor_collector.build_fragments_get_exclude_head ();
 731
 732         /* clear scan starts */
 733         memset (nursery_section->scan_starts, 0, nursery_section->num_scan_start * sizeof (gpointer));
 734
 735         pin_start = pin_entry = sgen_pinning_get_entry (nursery_section->pin_queue_first_entry);
 736         pin_end = sgen_pinning_get_entry (nursery_section->pin_queue_last_entry);
 737
 738         while (pin_entry < pin_end || frags_ranges) {
 739                 char *addr0, *addr1;
 740                 size_t size;
 741
 742                 addr0 = addr1 = sgen_nursery_end;
 743                 if (pin_entry < pin_end)
 744                         addr0 = (char *)*pin_entry;
 745                 if (frags_ranges)
 746                         addr1 = frags_ranges->fragment_start;
 747
 748                 if (addr0 < addr1) {
 749                         SGEN_UNPIN_OBJECT (addr0);
 750                         size = SGEN_ALIGN_UP (sgen_safe_object_get_size ((GCObject*)addr0));
 751                         CANARIFY_SIZE (size);
 752                         sgen_set_nursery_scan_start (addr0);
 753                         frag_end = addr0;
 754                         ++pin_entry;
 755                 } else {
 756                         frag_end = addr1;
 757                         size = frags_ranges->fragment_next - addr1;
 758                         frags_ranges = frags_ranges->next_in_order;
 759                 }
 760
 761                 frag_size = frag_end - frag_start;
 762
 763                 if (size == 0)
 764                         continue;
 765
 766                 g_assert (frag_size >= 0);
 767                 g_assert (size > 0);
 768                 if (frag_size && size)
 769                         add_nursery_frag_checks (&mutator_allocator, frag_start, frag_end);
 770
 771                 frag_size = size;
 772 #ifdef NALLOC_DEBUG
 773                 add_alloc_record (*pin_entry, frag_size, PINNING);
 774 #endif
 775                 frag_start = frag_end + frag_size;
 776         }
 777
 778         frag_end = sgen_nursery_end;
 779         frag_size = frag_end - frag_start;
 780         if (frag_size)
 781                 add_nursery_frag_checks (&mutator_allocator, frag_start, frag_end);
 782
 783         /* Now it's safe to release the fragments exclude list. */
 784         sgen_minor_collector.build_fragments_release_exclude_head ();
 785
 786         /* First we reorder the fragment list to be in ascending address order. This makes H/W prefetchers happier. */
 787         fragment_list_reverse (&mutator_allocator);
 788
 789         /*The collector might want to do something with the final nursery fragment list.*/
 790         sgen_minor_collector.build_fragments_finish (&mutator_allocator);
 791
 792         if (!unmask (mutator_allocator.alloc_head)) {
 793                 SGEN_LOG (1, "Nursery fully pinned");
 794                 for (pin_entry = pin_start; pin_entry < pin_end; ++pin_entry) {
 795                         GCObject *p = (GCObject *)*pin_entry;
 796                         SGEN_LOG (3, "Bastard pinning obj %p (%s), size: %ld", p, sgen_client_vtable_get_name (SGEN_LOAD_VTABLE (p)), (long)sgen_safe_object_get_size (p));
 797                 }
 798         }
 799         return fragment_total;
 800 }
 801
 802 /*** Nursery memory allocation ***/
 803 void
 804 sgen_nursery_retire_region (void *address, ptrdiff_t size)
 805 {
 806         HEAVY_STAT (stat_wasted_bytes_discarded_fragments += size);
 807 }
 808
 809 gboolean
 810 sgen_can_alloc_size (size_t size)
 811 {
 812         SgenFragment *frag;
 813
 814         if (!SGEN_CAN_ALIGN_UP (size))
 815                 return FALSE;
 816
 817         size = SGEN_ALIGN_UP (size);
 818
 819         for (frag = (SgenFragment *)unmask (mutator_allocator.alloc_head); frag; frag = (SgenFragment *)unmask (frag->next)) {
 820                 if ((size_t)(frag->fragment_end - frag->fragment_next) >= size)
 821                         return TRUE;
 822         }
 823         return FALSE;
 824 }
 825
 826 void*
 827 sgen_nursery_alloc (size_t size)
 828 {
 829         SGEN_ASSERT (1, size >= (SGEN_CLIENT_MINIMUM_OBJECT_SIZE + CANARY_SIZE) && size <= (SGEN_MAX_SMALL_OBJ_SIZE + CANARY_SIZE), "Invalid nursery object size");
 830
 831         SGEN_LOG (4, "Searching nursery for size: %zd", size);
 832         size = SGEN_ALIGN_UP (size);
 833
 834         HEAVY_STAT (++stat_nursery_alloc_requests);
 835
 836         return sgen_fragment_allocator_par_alloc (&mutator_allocator, size);
 837 }
 838
 839 void*
 840 sgen_nursery_alloc_range (size_t desired_size, size_t minimum_size, size_t *out_alloc_size)
 841 {
 842         SGEN_LOG (4, "Searching for byte range desired size: %zd minimum size %zd", desired_size, minimum_size);
 843
 844         HEAVY_STAT (++stat_nursery_alloc_range_requests);
 845
 846         return sgen_fragment_allocator_par_range_alloc (&mutator_allocator, desired_size, minimum_size, out_alloc_size);
 847 }
 848
 849 /*** Initialization ***/
 850
 851 #ifdef HEAVY_STATISTICS
 852
 853 void
 854 sgen_nursery_allocator_init_heavy_stats (void)
 855 {
 856         mono_counters_register ("bytes wasted trailer fragments", MONO_COUNTER_GC | MONO_COUNTER_WORD | MONO_COUNTER_BYTES, &stat_wasted_bytes_trailer);
 857         mono_counters_register ("bytes wasted small areas", MONO_COUNTER_GC | MONO_COUNTER_WORD | MONO_COUNTER_BYTES, &stat_wasted_bytes_small_areas);
 858         mono_counters_register ("bytes wasted discarded fragments", MONO_COUNTER_GC | MONO_COUNTER_WORD | MONO_COUNTER_BYTES, &stat_wasted_bytes_discarded_fragments);
 859
 860         mono_counters_register ("# nursery alloc requests", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_nursery_alloc_requests);
 861         mono_counters_register ("# nursery alloc iterations", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_alloc_iterations);
 862         mono_counters_register ("# nursery alloc retries", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_alloc_retries);
 863
 864         mono_counters_register ("# nursery alloc range requests", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_nursery_alloc_range_requests);
 865         mono_counters_register ("# nursery alloc range iterations", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_alloc_range_iterations);
 866         mono_counters_register ("# nursery alloc range restries", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_alloc_range_retries);
 867 }
 868
 869 #endif
 870
 871 void
 872 sgen_init_nursery_allocator (void)
 873 {
 874         sgen_register_fixed_internal_mem_type (INTERNAL_MEM_FRAGMENT, sizeof (SgenFragment));
 875 #ifdef NALLOC_DEBUG
 876         alloc_records = sgen_alloc_os_memory (sizeof (AllocRecord) * ALLOC_RECORD_COUNT, SGEN_ALLOC_INTERNAL | SGEN_ALLOC_ACTIVATE, "debugging memory");
 877 #endif
 878 }
 879
 880 void
 881 sgen_nursery_alloc_prepare_for_minor (void)
 882 {
 883         sgen_minor_collector.prepare_to_space (sgen_space_bitmap, sgen_space_bitmap_size);
 884 }
 885
 886 void
 887 sgen_nursery_alloc_prepare_for_major (void)
 888 {
 889         sgen_minor_collector.prepare_to_space (sgen_space_bitmap, sgen_space_bitmap_size);
 890 }
 891
 892 void
 893 sgen_nursery_allocator_set_nursery_bounds (char *start, size_t min_size, size_t max_size)
 894 {
 895         sgen_nursery_start = start;
 896         sgen_nursery_end = start + max_size;
 897
 898         sgen_nursery_size = min_size;
 899         sgen_nursery_min_size = min_size;
 900         sgen_nursery_max_size = max_size;
 901
 902         sgen_nursery_bits = 0;
 903         while (ONE_P << (++ sgen_nursery_bits) != sgen_nursery_max_size)
 904                 ;
 905
 906         /*
 907          * This will not divide evenly for tiny nurseries (<4kb), so we make sure to be on
 908          * the right side of things and round up.  We could just do a MIN(1,x) instead,
 909          * since the nursery size must be a power of 2.
 910          */
 911         sgen_space_bitmap_size = (sgen_nursery_end - sgen_nursery_start + SGEN_TO_SPACE_GRANULE_IN_BYTES * 8 - 1) / (SGEN_TO_SPACE_GRANULE_IN_BYTES * 8);
 912         sgen_space_bitmap = (char *)g_malloc0 (sgen_space_bitmap_size);
 913
 914         /* Setup the single first large fragment */
 915         sgen_minor_collector.init_nursery (&mutator_allocator, sgen_nursery_start, sgen_nursery_end);
 916 }
 917
 918 void
 919 sgen_resize_nursery (gboolean need_shrink)
 920 {
 921         size_t major_size;
 922
 923         if (sgen_nursery_min_size == sgen_nursery_max_size)
 924                 return;
 925
 926         major_size = sgen_major_collector.get_num_major_sections () * sgen_major_collector.section_size + sgen_los_memory_usage;
 927         /*
 928          * We attempt to use a larger nursery size, as long as it doesn't
 929          * exceed a certain percentage of the major heap.
 930          *
 931          * FIXME
 932          * Commit memory when expanding and release it when shrinking (which
 933          * would only be possible if there aren't any pinned objects in the
 934          * section).
 935          */
 936         if ((sgen_nursery_size * 2) < (major_size / SGEN_DEFAULT_ALLOWANCE_NURSERY_SIZE_RATIO) &&
 937                         (sgen_nursery_size * 2) <= sgen_nursery_max_size && !need_shrink) {
 938                 if ((sgen_nursery_section->end_data - sgen_nursery_section->data) == sgen_nursery_size)
 939                         sgen_nursery_section->end_data += sgen_nursery_size;
 940                 sgen_nursery_size *= 2;
 941         } else if ((sgen_nursery_size > (major_size / SGEN_DEFAULT_ALLOWANCE_NURSERY_SIZE_RATIO) || need_shrink) &&
 942                         (sgen_nursery_size / 2) >= sgen_nursery_min_size) {
 943                 sgen_nursery_size /= 2;
 944         }
 945 }
 946
 947
 948 #endif