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
 223 static inline gpointer
 224 mask (gpointer n, uintptr_t bit)
 225 {
 226         return (gpointer)(((uintptr_t)n) | bit);
 227 }
 228
 229 static inline gpointer
 230 unmask (gpointer p)
 231 {
 232         return (gpointer)((uintptr_t)p & ~(uintptr_t)0x3);
 233 }
 234
 235 static inline uintptr_t
 236 get_mark (gpointer n)
 237 {
 238         return (uintptr_t)n & 0x1;
 239 }
 240
 241 /*MUST be called with world stopped*/
 242 SgenFragment*
 243 sgen_fragment_allocator_alloc (void)
 244 {
 245         SgenFragment *frag = fragment_freelist;
 246         if (frag) {
 247                 fragment_freelist = frag->next_in_order;
 248                 frag->next = frag->next_in_order = NULL;
 249                 return frag;
 250         }
 251         frag = (SgenFragment *)sgen_alloc_internal (INTERNAL_MEM_FRAGMENT);
 252         frag->next = frag->next_in_order = NULL;
 253         return frag;
 254 }
 255
 256 void
 257 sgen_fragment_allocator_add (SgenFragmentAllocator *allocator, char *start, char *end)
 258 {
 259         SgenFragment *fragment;
 260
 261         fragment = sgen_fragment_allocator_alloc ();
 262         fragment->fragment_start = start;
 263         fragment->fragment_next = start;
 264         fragment->fragment_end = end;
 265         fragment->next_in_order = fragment->next = (SgenFragment *)unmask (allocator->region_head);
 266
 267         allocator->region_head = allocator->alloc_head = fragment;
 268         g_assert (fragment->fragment_end > fragment->fragment_start);
 269 }
 270
 271 void
 272 sgen_fragment_allocator_release (SgenFragmentAllocator *allocator)
 273 {
 274         SgenFragment *last = allocator->region_head;
 275         if (!last)
 276                 return;
 277
 278         /* Find the last fragment in insert order */
 279         for (; last->next_in_order; last = last->next_in_order) ;
 280
 281         last->next_in_order = fragment_freelist;
 282         fragment_freelist = allocator->region_head;
 283         allocator->alloc_head = allocator->region_head = NULL;
 284 }
 285
 286 static SgenFragment**
 287 find_previous_pointer_fragment (SgenFragmentAllocator *allocator, SgenFragment *frag)
 288 {
 289         SgenFragment **prev;
 290         SgenFragment *cur, *next;
 291 #ifdef NALLOC_DEBUG
 292         int count = 0;
 293 #endif
 294
 295 try_again:
 296         prev = &allocator->alloc_head;
 297 #ifdef NALLOC_DEBUG
 298         if (count++ > 5)
 299                 printf ("retry count for fppf is %d\n", count);
 300 #endif
 301
 302         cur = (SgenFragment *)unmask (*prev);
 303
 304         while (1) {
 305                 if (cur == NULL)
 306                         return NULL;
 307                 next = cur->next;
 308
 309                 /*
 310                  * We need to make sure that we dereference prev below
 311                  * after reading cur->next above, so we need a read
 312                  * barrier.
 313                  */
 314                 mono_memory_read_barrier ();
 315
 316                 if (*prev != cur)
 317                         goto try_again;
 318
 319                 if (!get_mark (next)) {
 320                         if (cur == frag)
 321                                 return prev;
 322                         prev = &cur->next;
 323                 } else {
 324                         next = (SgenFragment *)unmask (next);
 325                         if (mono_atomic_cas_ptr ((volatile gpointer*)prev, next, cur) != cur)
 326                                 goto try_again;
 327                         /*we must make sure that the next from cur->next happens after*/
 328                         mono_memory_write_barrier ();
 329                 }
 330
 331                 cur = (SgenFragment *)unmask (next);
 332         }
 333         return NULL;
 334 }
 335
 336 static gboolean
 337 claim_remaining_size (SgenFragment *frag, char *alloc_end)
 338 {
 339         /* All space used, nothing to claim. */
 340         if (frag->fragment_end <= alloc_end)
 341                 return FALSE;
 342
 343         /* Try to alloc all the remaining space. */
 344         return mono_atomic_cas_ptr ((volatile gpointer*)&frag->fragment_next, frag->fragment_end, alloc_end) == alloc_end;
 345 }
 346
 347 static void*
 348 par_alloc_from_fragment (SgenFragmentAllocator *allocator, SgenFragment *frag, size_t size)
 349 {
 350         char *p = frag->fragment_next;
 351         char *end = p + size;
 352
 353         if (end > frag->fragment_end || end > (sgen_nursery_start + sgen_nursery_size))
 354                 return NULL;
 355
 356         /* p = frag->fragment_next must happen before */
 357         mono_memory_barrier ();
 358
 359         if (mono_atomic_cas_ptr ((volatile gpointer*)&frag->fragment_next, end, p) != p)
 360                 return NULL;
 361
 362         if (frag->fragment_end - end < SGEN_MAX_NURSERY_WASTE) {
 363                 SgenFragment *next, **prev_ptr;
 364
 365                 /*
 366                  * Before we clean the remaining nursery, we must claim the remaining space
 367                  * as it could end up been used by the range allocator since it can end up
 368                  * allocating from this dying fragment as it doesn't respect SGEN_MAX_NURSERY_WASTE
 369                  * when doing second chance allocation.
 370                  */
 371                 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)) {
 372                         sgen_clear_range (end, frag->fragment_end);
 373                         HEAVY_STAT (stat_wasted_bytes_trailer += frag->fragment_end - end);
 374 #ifdef NALLOC_DEBUG
 375                         add_alloc_record (end, frag->fragment_end - end, BLOCK_ZEROING);
 376 #endif
 377                 }
 378
 379                 prev_ptr = find_previous_pointer_fragment (allocator, frag);
 380
 381                 /*Use Michaels linked list remove*/
 382
 383                 /*prev_ptr will be null if the fragment was removed concurrently */
 384                 while (prev_ptr) {
 385                         next = frag->next;
 386
 387                         /*already deleted*/
 388                         if (!get_mark (next)) {
 389                                 /*frag->next read must happen before the first CAS*/
 390                                 mono_memory_write_barrier ();
 391
 392                                 /*Fail if the next node is removed concurrently and its CAS wins */
 393                                 if (mono_atomic_cas_ptr ((volatile gpointer*)&frag->next, mask (next, 1), next) != next) {
 394                                         continue;
 395                                 }
 396                         }
 397
 398                         /* The second CAS must happen after the first CAS or frag->next. */
 399                         mono_memory_write_barrier ();
 400
 401                         /* Fail if the previous node was deleted and its CAS wins */
 402                         if (mono_atomic_cas_ptr ((volatile gpointer*)prev_ptr, unmask (next), frag) != frag) {
 403                                 prev_ptr = find_previous_pointer_fragment (allocator, frag);
 404                                 continue;
 405                         }
 406                         break;
 407                 }
 408         }
 409
 410         return p;
 411 }
 412
 413 static void*
 414 serial_alloc_from_fragment (SgenFragment **previous, SgenFragment *frag, size_t size)
 415 {
 416         char *p = frag->fragment_next;
 417         char *end = p + size;
 418
 419         if (end > frag->fragment_end)
 420                 return NULL;
 421
 422         frag->fragment_next = end;
 423
 424         if (frag->fragment_end - end < SGEN_MAX_NURSERY_WASTE) {
 425                 *previous = frag->next;
 426
 427                 /* Clear the remaining space, pinning depends on this. FIXME move this to use phony arrays */
 428                 memset (end, 0, frag->fragment_end - end);
 429
 430                 *previous = frag->next;
 431         }
 432
 433         return p;
 434 }
 435
 436 void*
 437 sgen_fragment_allocator_par_alloc (SgenFragmentAllocator *allocator, size_t size)
 438 {
 439         SgenFragment *frag;
 440
 441 #ifdef NALLOC_DEBUG
 442         mono_atomic_inc_i32 (&alloc_count);
 443 #endif
 444
 445 restart:
 446         for (frag = (SgenFragment *)unmask (allocator->alloc_head); unmask (frag); frag = (SgenFragment *)unmask (frag->next)) {
 447                 size_t frag_size = frag->fragment_end - frag->fragment_next;
 448
 449                 if (frag->fragment_next >= (sgen_nursery_start + sgen_nursery_size))
 450                         continue;
 451
 452                 HEAVY_STAT (++stat_alloc_iterations);
 453
 454                 if (size <= frag_size) {
 455                         void *p = par_alloc_from_fragment (allocator, frag, size);
 456                         if (!p) {
 457                                 HEAVY_STAT (++stat_alloc_retries);
 458                                 goto restart;
 459                         }
 460 #ifdef NALLOC_DEBUG
 461                         add_alloc_record (p, size, FIXED_ALLOC);
 462 #endif
 463                         return p;
 464                 }
 465         }
 466         return NULL;
 467 }
 468
 469 void*
 470 sgen_fragment_allocator_serial_range_alloc (SgenFragmentAllocator *allocator, size_t desired_size, size_t minimum_size, size_t *out_alloc_size)
 471 {
 472         SgenFragment *frag, **previous, *min_frag = NULL, **prev_min_frag = NULL;
 473         size_t current_minimum = minimum_size;
 474
 475 #ifdef NALLOC_DEBUG
 476         mono_atomic_inc_i32 (&alloc_count);
 477 #endif
 478
 479         previous = &allocator->alloc_head;
 480
 481         for (frag = *previous; frag; frag = *previous) {
 482                 size_t frag_size = frag->fragment_end - frag->fragment_next;
 483
 484                 HEAVY_STAT (++stat_alloc_range_iterations);
 485
 486                 if (desired_size <= frag_size) {
 487                         void *p;
 488                         *out_alloc_size = desired_size;
 489
 490                         p = serial_alloc_from_fragment (previous, frag, desired_size);
 491 #ifdef NALLOC_DEBUG
 492                         add_alloc_record (p, desired_size, RANGE_ALLOC);
 493 #endif
 494                         return p;
 495                 }
 496                 if (current_minimum <= frag_size) {
 497                         min_frag = frag;
 498                         prev_min_frag = previous;
 499                         current_minimum = frag_size;
 500                 }
 501                 previous = &frag->next;
 502         }
 503
 504         if (min_frag) {
 505                 void *p;
 506                 size_t frag_size = min_frag->fragment_end - min_frag->fragment_next;
 507                 *out_alloc_size = frag_size;
 508
 509                 p = serial_alloc_from_fragment (prev_min_frag, min_frag, frag_size);
 510
 511 #ifdef NALLOC_DEBUG
 512                 add_alloc_record (p, frag_size, RANGE_ALLOC);
 513 #endif
 514                 return p;
 515         }
 516
 517         return NULL;
 518 }
 519
 520 void*
 521 sgen_fragment_allocator_par_range_alloc (SgenFragmentAllocator *allocator, size_t desired_size, size_t minimum_size, size_t *out_alloc_size)
 522 {
 523         SgenFragment *frag, *min_frag;
 524         size_t current_minimum;
 525
 526 restart:
 527         min_frag = NULL;
 528         current_minimum = minimum_size;
 529
 530 #ifdef NALLOC_DEBUG
 531         mono_atomic_inc_i32 (&alloc_count);
 532 #endif
 533
 534         for (frag = (SgenFragment *)unmask (allocator->alloc_head); frag; frag = (SgenFragment *)unmask (frag->next)) {
 535                 size_t frag_size = frag->fragment_end - frag->fragment_next;
 536
 537                 if (frag->fragment_next >= (sgen_nursery_start + sgen_nursery_size))
 538                         continue;
 539
 540                 HEAVY_STAT (++stat_alloc_range_iterations);
 541
 542                 if (desired_size <= frag_size) {
 543                         void *p;
 544                         *out_alloc_size = desired_size;
 545
 546                         p = par_alloc_from_fragment (allocator, frag, desired_size);
 547                         if (!p) {
 548                                 HEAVY_STAT (++stat_alloc_range_retries);
 549                                 goto restart;
 550                         }
 551 #ifdef NALLOC_DEBUG
 552                         add_alloc_record (p, desired_size, RANGE_ALLOC);
 553 #endif
 554                         return p;
 555                 }
 556                 if (current_minimum <= frag_size) {
 557                         min_frag = frag;
 558                         current_minimum = frag_size;
 559                 }
 560         }
 561
 562         /* The second fragment_next read should be ordered in respect to the first code block */
 563         mono_memory_barrier ();
 564
 565         if (min_frag) {
 566                 void *p;
 567                 size_t frag_size = min_frag->fragment_end - min_frag->fragment_next;
 568
 569                 if (frag_size < minimum_size)
 570                         goto restart;
 571
 572                 *out_alloc_size = frag_size;
 573
 574                 mono_memory_barrier ();
 575                 p = par_alloc_from_fragment (allocator, min_frag, frag_size);
 576
 577                 /*XXX restarting here is quite dubious given this is already second chance allocation. */
 578                 if (!p) {
 579                         HEAVY_STAT (++stat_alloc_retries);
 580                         goto restart;
 581                 }
 582 #ifdef NALLOC_DEBUG
 583                 add_alloc_record (p, frag_size, RANGE_ALLOC);
 584 #endif
 585                 return p;
 586         }
 587
 588         return NULL;
 589 }
 590
 591 void
 592 sgen_clear_allocator_fragments (SgenFragmentAllocator *allocator)
 593 {
 594         SgenFragment *frag;
 595
 596         for (frag = (SgenFragment *)unmask (allocator->alloc_head); frag; frag = (SgenFragment *)unmask (frag->next)) {
 597                 SGEN_LOG (4, "Clear nursery frag %p-%p", frag->fragment_next, frag->fragment_end);
 598                 sgen_clear_range (frag->fragment_next, frag->fragment_end);
 599 #ifdef NALLOC_DEBUG
 600                 add_alloc_record (frag->fragment_next, frag->fragment_end - frag->fragment_next, CLEAR_NURSERY_FRAGS);
 601 #endif
 602         }
 603 }
 604
 605 /* Clear all remaining nursery fragments */
 606 void
 607 sgen_clear_nursery_fragments (void)
 608 {
 609         if (sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION || sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION_DEBUG) {
 610                 sgen_clear_allocator_fragments (&mutator_allocator);
 611                 sgen_minor_collector.clear_fragments ();
 612         }
 613 }
 614
 615 /*
 616  * Mark a given range of memory as invalid.
 617  *
 618  * This can be done either by zeroing memory or by placing
 619  * a phony byte[] array. This keeps the heap forward walkable.
 620  *
 621  * This function ignores calls with a zero range, even if
 622  * both start and end are NULL.
 623  */
 624 void
 625 sgen_clear_range (char *start, char *end)
 626 {
 627         size_t size = end - start;
 628
 629         if ((start && !end) || (start > end))
 630                 g_error ("Invalid range [%p %p]", start, end);
 631
 632         if (sgen_client_array_fill_range (start, size)) {
 633                 sgen_set_nursery_scan_start (start);
 634                 SGEN_ASSERT (0, start + sgen_safe_object_get_size ((GCObject*)start) == end, "Array fill produced wrong size");
 635         }
 636 }
 637
 638 void
 639 sgen_nursery_allocator_prepare_for_pinning (void)
 640 {
 641         sgen_clear_allocator_fragments (&mutator_allocator);
 642         sgen_minor_collector.clear_fragments ();
 643 }
 644
 645 static mword fragment_total = 0;
 646 /*
 647  * We found a fragment of free memory in the nursery: memzero it and if
 648  * it is big enough, add it to the list of fragments that can be used for
 649  * allocation.
 650  */
 651 static void
 652 add_nursery_frag (SgenFragmentAllocator *allocator, size_t frag_size, char* frag_start, char* frag_end)
 653 {
 654         SGEN_LOG (4, "Found empty fragment: %p-%p, size: %zd", frag_start, frag_end, frag_size);
 655         sgen_binary_protocol_empty (frag_start, frag_size);
 656         /* Not worth dealing with smaller fragments: need to tune */
 657         if (frag_size >= SGEN_MAX_NURSERY_WASTE) {
 658                 /* memsetting just the first chunk start is bound to provide better cache locality */
 659                 if (sgen_get_nursery_clear_policy () == CLEAR_AT_GC)
 660                         memset (frag_start, 0, frag_size);
 661                 else if (sgen_get_nursery_clear_policy () == CLEAR_AT_TLAB_CREATION_DEBUG)
 662                         memset (frag_start, 0xff, frag_size);
 663
 664 #ifdef NALLOC_DEBUG
 665                 /* XXX convert this into a flight record entry
 666                 printf ("\tfragment [%p %p] size %zd\n", frag_start, frag_end, frag_size);
 667                 */
 668 #endif
 669                 sgen_fragment_allocator_add (allocator, frag_start, frag_end);
 670                 fragment_total += frag_size;
 671         } else {
 672                 /* Clear unused fragments, pinning depends on this */
 673                 sgen_clear_range (frag_start, frag_end);
 674                 HEAVY_STAT (stat_wasted_bytes_small_areas += frag_size);
 675         }
 676 }
 677
 678 static void
 679 fragment_list_reverse (SgenFragmentAllocator *allocator)
 680 {
 681         SgenFragment *prev = NULL, *list = allocator->region_head;
 682         while (list) {
 683                 SgenFragment *next = list->next;
 684                 list->next = prev;
 685                 list->next_in_order = prev;
 686                 prev = list;
 687                 list = next;
 688         }
 689
 690         allocator->region_head = allocator->alloc_head = prev;
 691 }
 692
 693 /*
 694  * We split fragments at the border of the current nursery limit. When we
 695  * allocate from the nursery we only consider fragments that start in the
 696  * current nursery section. We build fragments for the entire nursery in
 697  * order to facilitate scanning it for objects (adding a nursery frag also
 698  * marks a region in the nursery as being free)
 699  */
 700 static void
 701 add_nursery_frag_checks (SgenFragmentAllocator *allocator, char *frag_start, char *frag_end)
 702 {
 703         char *nursery_limit = sgen_nursery_start + sgen_nursery_size;
 704
 705         if (frag_start < nursery_limit && frag_end > nursery_limit) {
 706                 add_nursery_frag (allocator, nursery_limit - frag_start, frag_start, nursery_limit);
 707                 add_nursery_frag (allocator, frag_end - nursery_limit, nursery_limit, frag_end);
 708         } else {
 709                 add_nursery_frag (allocator, frag_end - frag_start, frag_start, frag_end);
 710         }
 711 }
 712
 713 mword
 714 sgen_build_nursery_fragments (GCMemSection *nursery_section, SgenGrayQueue *unpin_queue)
 715 {
 716         char *frag_start, *frag_end;
 717         size_t frag_size;
 718         SgenFragment *frags_ranges;
 719         void **pin_start, **pin_entry, **pin_end;
 720
 721 #ifdef NALLOC_DEBUG
 722         reset_alloc_records ();
 723 #endif
 724         /*The mutator fragments are done. We no longer need them. */
 725         sgen_fragment_allocator_release (&mutator_allocator);
 726
 727         frag_start = sgen_nursery_start;
 728         fragment_total = 0;
 729
 730         /* The current nursery might give us a fragment list to exclude [start, next[*/
 731         frags_ranges = sgen_minor_collector.build_fragments_get_exclude_head ();
 732
 733         /* clear scan starts */
 734         memset (nursery_section->scan_starts, 0, nursery_section->num_scan_start * sizeof (gpointer));
 735
 736         pin_start = pin_entry = sgen_pinning_get_entry (nursery_section->pin_queue_first_entry);
 737         pin_end = sgen_pinning_get_entry (nursery_section->pin_queue_last_entry);
 738
 739         while (pin_entry < pin_end || frags_ranges) {
 740                 char *addr0, *addr1;
 741                 size_t size;
 742
 743                 addr0 = addr1 = sgen_nursery_end;
 744                 if (pin_entry < pin_end)
 745                         addr0 = (char *)*pin_entry;
 746                 if (frags_ranges)
 747                         addr1 = frags_ranges->fragment_start;
 748
 749                 if (addr0 < addr1) {
 750                         if (unpin_queue)
 751                                 GRAY_OBJECT_ENQUEUE_SERIAL (unpin_queue, (GCObject*)addr0, sgen_obj_get_descriptor_safe ((GCObject*)addr0));
 752                         else
 753                                 SGEN_UNPIN_OBJECT (addr0);
 754                         size = SGEN_ALIGN_UP (sgen_safe_object_get_size ((GCObject*)addr0));
 755                         CANARIFY_SIZE (size);
 756                         sgen_set_nursery_scan_start (addr0);
 757                         frag_end = addr0;
 758                         ++pin_entry;
 759                 } else {
 760                         frag_end = addr1;
 761                         size = frags_ranges->fragment_next - addr1;
 762                         frags_ranges = frags_ranges->next_in_order;
 763                 }
 764
 765                 frag_size = frag_end - frag_start;
 766
 767                 if (size == 0)
 768                         continue;
 769
 770                 g_assert (frag_size >= 0);
 771                 g_assert (size > 0);
 772                 if (frag_size && size)
 773                         add_nursery_frag_checks (&mutator_allocator, frag_start, frag_end);
 774
 775                 frag_size = size;
 776 #ifdef NALLOC_DEBUG
 777                 add_alloc_record (*pin_entry, frag_size, PINNING);
 778 #endif
 779                 frag_start = frag_end + frag_size;
 780         }
 781
 782         frag_end = sgen_nursery_end;
 783         frag_size = frag_end - frag_start;
 784         if (frag_size)
 785                 add_nursery_frag_checks (&mutator_allocator, frag_start, frag_end);
 786
 787         /* Now it's safe to release the fragments exclude list. */
 788         sgen_minor_collector.build_fragments_release_exclude_head ();
 789
 790         /* First we reorder the fragment list to be in ascending address order. This makes H/W prefetchers happier. */
 791         fragment_list_reverse (&mutator_allocator);
 792
 793         /*The collector might want to do something with the final nursery fragment list.*/
 794         sgen_minor_collector.build_fragments_finish (&mutator_allocator);
 795
 796         if (!unmask (mutator_allocator.alloc_head)) {
 797                 SGEN_LOG (1, "Nursery fully pinned");
 798                 for (pin_entry = pin_start; pin_entry < pin_end; ++pin_entry) {
 799                         GCObject *p = (GCObject *)*pin_entry;
 800                         SGEN_LOG (3, "Bastard pinning obj %p (%s), size: %zd", p, sgen_client_vtable_get_name (SGEN_LOAD_VTABLE (p)), sgen_safe_object_get_size (p));
 801                 }
 802         }
 803         return fragment_total;
 804 }
 805
 806 /*** Nursery memory allocation ***/
 807 void
 808 sgen_nursery_retire_region (void *address, ptrdiff_t size)
 809 {
 810         HEAVY_STAT (stat_wasted_bytes_discarded_fragments += size);
 811 }
 812
 813 gboolean
 814 sgen_can_alloc_size (size_t size)
 815 {
 816         SgenFragment *frag;
 817
 818         if (!SGEN_CAN_ALIGN_UP (size))
 819                 return FALSE;
 820
 821         size = SGEN_ALIGN_UP (size);
 822
 823         for (frag = (SgenFragment *)unmask (mutator_allocator.alloc_head); frag; frag = (SgenFragment *)unmask (frag->next)) {
 824                 if ((size_t)(frag->fragment_end - frag->fragment_next) >= size)
 825                         return TRUE;
 826         }
 827         return FALSE;
 828 }
 829
 830 void*
 831 sgen_nursery_alloc (size_t size)
 832 {
 833         SGEN_ASSERT (1, size >= (SGEN_CLIENT_MINIMUM_OBJECT_SIZE + CANARY_SIZE) && size <= (SGEN_MAX_SMALL_OBJ_SIZE + CANARY_SIZE), "Invalid nursery object size");
 834
 835         SGEN_LOG (4, "Searching nursery for size: %zd", size);
 836         size = SGEN_ALIGN_UP (size);
 837
 838         HEAVY_STAT (++stat_nursery_alloc_requests);
 839
 840         return sgen_fragment_allocator_par_alloc (&mutator_allocator, size);
 841 }
 842
 843 void*
 844 sgen_nursery_alloc_range (size_t desired_size, size_t minimum_size, size_t *out_alloc_size)
 845 {
 846         SGEN_LOG (4, "Searching for byte range desired size: %zd minimum size %zd", desired_size, minimum_size);
 847
 848         HEAVY_STAT (++stat_nursery_alloc_range_requests);
 849
 850         return sgen_fragment_allocator_par_range_alloc (&mutator_allocator, desired_size, minimum_size, out_alloc_size);
 851 }
 852
 853 /*** Initialization ***/
 854
 855 #ifdef HEAVY_STATISTICS
 856
 857 void
 858 sgen_nursery_allocator_init_heavy_stats (void)
 859 {
 860         mono_counters_register ("bytes wasted trailer fragments", MONO_COUNTER_GC | MONO_COUNTER_WORD | MONO_COUNTER_BYTES, &stat_wasted_bytes_trailer);
 861         mono_counters_register ("bytes wasted small areas", MONO_COUNTER_GC | MONO_COUNTER_WORD | MONO_COUNTER_BYTES, &stat_wasted_bytes_small_areas);
 862         mono_counters_register ("bytes wasted discarded fragments", MONO_COUNTER_GC | MONO_COUNTER_WORD | MONO_COUNTER_BYTES, &stat_wasted_bytes_discarded_fragments);
 863
 864         mono_counters_register ("# nursery alloc requests", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_nursery_alloc_requests);
 865         mono_counters_register ("# nursery alloc iterations", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_alloc_iterations);
 866         mono_counters_register ("# nursery alloc retries", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_alloc_retries);
 867
 868         mono_counters_register ("# nursery alloc range requests", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_nursery_alloc_range_requests);
 869         mono_counters_register ("# nursery alloc range iterations", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_alloc_range_iterations);
 870         mono_counters_register ("# nursery alloc range restries", MONO_COUNTER_GC | MONO_COUNTER_ULONG, &stat_alloc_range_retries);
 871 }
 872
 873 #endif
 874
 875 void
 876 sgen_init_nursery_allocator (void)
 877 {
 878         sgen_register_fixed_internal_mem_type (INTERNAL_MEM_FRAGMENT, sizeof (SgenFragment));
 879 #ifdef NALLOC_DEBUG
 880         alloc_records = sgen_alloc_os_memory (sizeof (AllocRecord) * ALLOC_RECORD_COUNT, SGEN_ALLOC_INTERNAL | SGEN_ALLOC_ACTIVATE, "debugging memory");
 881 #endif
 882 }
 883
 884 void
 885 sgen_nursery_alloc_prepare_for_minor (void)
 886 {
 887         sgen_minor_collector.prepare_to_space (sgen_space_bitmap, sgen_space_bitmap_size);
 888 }
 889
 890 void
 891 sgen_nursery_alloc_prepare_for_major (void)
 892 {
 893         sgen_minor_collector.prepare_to_space (sgen_space_bitmap, sgen_space_bitmap_size);
 894 }
 895
 896 void
 897 sgen_nursery_allocator_set_nursery_bounds (char *start, size_t min_size, size_t max_size)
 898 {
 899         sgen_nursery_start = start;
 900         sgen_nursery_end = start + max_size;
 901
 902         sgen_nursery_size = min_size;
 903         sgen_nursery_min_size = min_size;
 904         sgen_nursery_max_size = max_size;
 905
 906         sgen_nursery_bits = 0;
 907         while (ONE_P << (++ sgen_nursery_bits) != sgen_nursery_max_size)
 908                 ;
 909
 910         /*
 911          * This will not divide evenly for tiny nurseries (<4kb), so we make sure to be on
 912          * the right side of things and round up.  We could just do a MIN(1,x) instead,
 913          * since the nursery size must be a power of 2.
 914          */
 915         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);
 916         sgen_space_bitmap = (char *)g_malloc0 (sgen_space_bitmap_size);
 917
 918         /* Setup the single first large fragment */
 919         sgen_minor_collector.init_nursery (&mutator_allocator, sgen_nursery_start, sgen_nursery_end);
 920 }
 921
 922 void
 923 sgen_resize_nursery (gboolean need_shrink)
 924 {
 925         size_t major_size;
 926
 927         if (sgen_nursery_min_size == sgen_nursery_max_size)
 928                 return;
 929
 930         major_size = sgen_major_collector.get_num_major_sections () * sgen_major_collector.section_size + sgen_los_memory_usage;
 931         /*
 932          * We attempt to use a larger nursery size, as long as it doesn't
 933          * exceed a certain percentage of the major heap.
 934          *
 935          * FIXME
 936          * Commit memory when expanding and release it when shrinking (which
 937          * would only be possible if there aren't any pinned objects in the
 938          * section).
 939          */
 940         if ((sgen_nursery_size * 2) < (major_size / SGEN_DEFAULT_ALLOWANCE_NURSERY_SIZE_RATIO) &&
 941                         (sgen_nursery_size * 2) <= sgen_nursery_max_size && !need_shrink) {
 942                 if ((sgen_nursery_section->end_data - sgen_nursery_section->data) == sgen_nursery_size)
 943                         sgen_nursery_section->end_data += sgen_nursery_size;
 944                 sgen_nursery_size *= 2;
 945         } else if ((sgen_nursery_size > (major_size / SGEN_DEFAULT_ALLOWANCE_NURSERY_SIZE_RATIO) || need_shrink) &&
 946                         (sgen_nursery_size / 2) >= sgen_nursery_min_size) {
 947                 sgen_nursery_size /= 2;
 948         }
 949 }
 950
 951
 952 #endif