jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp@2ace1c4ee8da (annotated)

src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp@2ace1c4ee8da (annotated)

src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp

Tue, 10 Jan 2012 18:58:13 -0500

author: tonyp
date: Tue, 10 Jan 2012 18:58:13 -0500
changeset 3416: 2ace1c4ee8da
parent 2453: 2250ee17e258
child 3900: d2a62e0f25eb
permissions: -rw-r--r--

6888336: G1: avoid explicitly marking and pushing objects in survivor spaces
Summary: This change simplifies the interaction between GC and concurrent marking. By disabling survivor spaces during the initial-mark pause we don't need to propagate marks of objects we copy during each GC (since we never need to copy an explicitly marked object).
Reviewed-by: johnc, brutisso

 /*
  * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP
 #include "memory/memRegion.hpp"
 #include "runtime/virtualspace.hpp"
 #include "utilities/globalDefinitions.hpp"
 // The CollectedHeap type requires subtypes to implement a method
 // "block_start".  For some subtypes, notably generational
 // systems using card-table-based write barriers, the efficiency of this
 // operation may be important.  Implementations of the "BlockOffsetArray"
 // class may be useful in providing such efficient implementations.
 //
 // While generally mirroring the structure of the BOT for GenCollectedHeap,
 // the following types are tailored more towards G1's uses; these should,
 // however, be merged back into a common BOT to avoid code duplication
 // and reduce maintenance overhead.
 //
 //    G1BlockOffsetTable (abstract)
 //    -- G1BlockOffsetArray                (uses G1BlockOffsetSharedArray)
 //       -- G1BlockOffsetArrayContigSpace
 //
 // A main impediment to the consolidation of this code might be the
 // effect of making some of the block_start*() calls non-const as
 // below. Whether that might adversely affect performance optimizations
 // that compilers might normally perform in the case of non-G1
 // collectors needs to be carefully investigated prior to any such
 // consolidation.
 // Forward declarations
 class ContiguousSpace;
 class G1BlockOffsetSharedArray;
 class G1BlockOffsetTable VALUE_OBJ_CLASS_SPEC {
   friend class VMStructs;
 protected:
   // These members describe the region covered by the table.
   // The space this table is covering.
   HeapWord* _bottom;    // == reserved.start
   HeapWord* _end;       // End of currently allocated region.
 public:
   // Initialize the table to cover the given space.
   // The contents of the initial table are undefined.
   G1BlockOffsetTable(HeapWord* bottom, HeapWord* end) :
     _bottom(bottom), _end(end)
     {
       assert(_bottom <= _end, "arguments out of order");
     }
   // Note that the committed size of the covered space may have changed,
   // so the table size might also wish to change.
   virtual void resize(size_t new_word_size) = 0;
   virtual void set_bottom(HeapWord* new_bottom) {
     assert(new_bottom <= _end, "new_bottom > _end");
     _bottom = new_bottom;
     resize(pointer_delta(_end, _bottom));
   }
   // Requires "addr" to be contained by a block, and returns the address of
   // the start of that block.  (May have side effects, namely updating of
   // shared array entries that "point" too far backwards.  This can occur,
   // for example, when LAB allocation is used in a space covered by the
   // table.)
   virtual HeapWord* block_start_unsafe(const void* addr) = 0;
   // Same as above, but does not have any of the possible side effects
   // discussed above.
   virtual HeapWord* block_start_unsafe_const(const void* addr) const = 0;
   // Returns the address of the start of the block containing "addr", or
   // else "null" if it is covered by no block.  (May have side effects,
   // namely updating of shared array entries that "point" too far
   // backwards.  This can occur, for example, when lab allocation is used
   // in a space covered by the table.)
   inline HeapWord* block_start(const void* addr);
   // Same as above, but does not have any of the possible side effects
   // discussed above.
   inline HeapWord* block_start_const(const void* addr) const;
 };
 // This implementation of "G1BlockOffsetTable" divides the covered region
 // into "N"-word subregions (where "N" = 2^"LogN".  An array with an entry
 // for each such subregion indicates how far back one must go to find the
 // start of the chunk that includes the first word of the subregion.
 //
 // Each BlockOffsetArray is owned by a Space.  However, the actual array
 // may be shared by several BlockOffsetArrays; this is useful
 // when a single resizable area (such as a generation) is divided up into
 // several spaces in which contiguous allocation takes place,
 // such as, for example, in G1 or in the train generation.)
 // Here is the shared array type.
 class G1BlockOffsetSharedArray: public CHeapObj {
   friend class G1BlockOffsetArray;
   friend class G1BlockOffsetArrayContigSpace;
   friend class VMStructs;
 private:
   // The reserved region covered by the shared array.
   MemRegion _reserved;
   // End of the current committed region.
   HeapWord* _end;
   // Array for keeping offsets for retrieving object start fast given an
   // address.
   VirtualSpace _vs;
   u_char* _offset_array;          // byte array keeping backwards offsets
   // Bounds checking accessors:
   // For performance these have to devolve to array accesses in product builds.
   u_char offset_array(size_t index) const {
     assert(index < _vs.committed_size(), "index out of range");
     return _offset_array[index];
   }
   void set_offset_array(size_t index, u_char offset) {
     assert(index < _vs.committed_size(), "index out of range");
     assert(offset <= N_words, "offset too large");
     _offset_array[index] = offset;
   }
   void set_offset_array(size_t index, HeapWord* high, HeapWord* low) {
     assert(index < _vs.committed_size(), "index out of range");
     assert(high >= low, "addresses out of order");
     assert(pointer_delta(high, low) <= N_words, "offset too large");
     _offset_array[index] = (u_char) pointer_delta(high, low);
   }
   void set_offset_array(HeapWord* left, HeapWord* right, u_char offset) {
     assert(index_for(right - 1) < _vs.committed_size(),
            "right address out of range");
     assert(left  < right, "Heap addresses out of order");
     size_t num_cards = pointer_delta(right, left) >> LogN_words;
     memset(&_offset_array[index_for(left)], offset, num_cards);
   }
   void set_offset_array(size_t left, size_t right, u_char offset) {
     assert(right < _vs.committed_size(), "right address out of range");
     assert(left  <= right, "indexes out of order");
     size_t num_cards = right - left + 1;
     memset(&_offset_array[left], offset, num_cards);
   }
   void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {
     assert(index < _vs.committed_size(), "index out of range");
     assert(high >= low, "addresses out of order");
     assert(pointer_delta(high, low) <= N_words, "offset too large");
     assert(_offset_array[index] == pointer_delta(high, low),
            "Wrong offset");
   }
   bool is_card_boundary(HeapWord* p) const;
   // Return the number of slots needed for an offset array
   // that covers mem_region_words words.
   // We always add an extra slot because if an object
   // ends on a card boundary we put a 0 in the next
   // offset array slot, so we want that slot always
   // to be reserved.
   size_t compute_size(size_t mem_region_words) {
     size_t number_of_slots = (mem_region_words / N_words) + 1;
     return ReservedSpace::page_align_size_up(number_of_slots);
   }
 public:
   enum SomePublicConstants {
     LogN = 9,
     LogN_words = LogN - LogHeapWordSize,
     N_bytes = 1 << LogN,
     N_words = 1 << LogN_words
   };
   // Initialize the table to cover from "base" to (at least)
   // "base + init_word_size".  In the future, the table may be expanded
   // (see "resize" below) up to the size of "_reserved" (which must be at
   // least "init_word_size".) The contents of the initial table are
   // undefined; it is the responsibility of the constituent
   // G1BlockOffsetTable(s) to initialize cards.
   G1BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size);
   // Notes a change in the committed size of the region covered by the
   // table.  The "new_word_size" may not be larger than the size of the
   // reserved region this table covers.
   void resize(size_t new_word_size);
   void set_bottom(HeapWord* new_bottom);
   // Updates all the BlockOffsetArray's sharing this shared array to
   // reflect the current "top"'s of their spaces.
   void update_offset_arrays();
   // Return the appropriate index into "_offset_array" for "p".
   inline size_t index_for(const void* p) const;
   // Return the address indicating the start of the region corresponding to
   // "index" in "_offset_array".
   inline HeapWord* address_for_index(size_t index) const;
 };
 // And here is the G1BlockOffsetTable subtype that uses the array.
 class G1BlockOffsetArray: public G1BlockOffsetTable {
   friend class G1BlockOffsetSharedArray;
   friend class G1BlockOffsetArrayContigSpace;
   friend class VMStructs;
 private:
   enum SomePrivateConstants {
     N_words = G1BlockOffsetSharedArray::N_words,
     LogN    = G1BlockOffsetSharedArray::LogN
   };
   // The following enums are used by do_block_helper
   enum Action {
     Action_single,      // BOT records a single block (see single_block())
     Action_mark,        // BOT marks the start of a block (see mark_block())
     Action_check        // Check that BOT records block correctly
                         // (see verify_single_block()).
   };
   // This is the array, which can be shared by several BlockOffsetArray's
   // servicing different
   G1BlockOffsetSharedArray* _array;
   // The space that owns this subregion.
   Space* _sp;
   // If "_sp" is a contiguous space, the field below is the view of "_sp"
   // as a contiguous space, else NULL.
   ContiguousSpace* _csp;
   // If true, array entries are initialized to 0; otherwise, they are
   // initialized to point backwards to the beginning of the covered region.
   bool _init_to_zero;
   // The portion [_unallocated_block, _sp.end()) of the space that
   // is a single block known not to contain any objects.
   // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag.
   HeapWord* _unallocated_block;
   // Sets the entries
   // corresponding to the cards starting at "start" and ending at "end"
   // to point back to the card before "start": the interval [start, end)
   // is right-open.
   void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end);
   // Same as above, except that the args here are a card _index_ interval
   // that is closed: [start_index, end_index]
   void set_remainder_to_point_to_start_incl(size_t start, size_t end);
   // A helper function for BOT adjustment/verification work
   void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action);
 protected:
   ContiguousSpace* csp() const { return _csp; }
   // Returns the address of a block whose start is at most "addr".
   // If "has_max_index" is true, "assumes "max_index" is the last valid one
   // in the array.
   inline HeapWord* block_at_or_preceding(const void* addr,
                                          bool has_max_index,
                                          size_t max_index) const;
   // "q" is a block boundary that is <= "addr"; "n" is the address of the
   // next block (or the end of the space.)  Return the address of the
   // beginning of the block that contains "addr".  Does so without side
   // effects (see, e.g., spec of  block_start.)
   inline HeapWord*
   forward_to_block_containing_addr_const(HeapWord* q, HeapWord* n,
                                          const void* addr) const;
   // "q" is a block boundary that is <= "addr"; return the address of the
   // beginning of the block that contains "addr".  May have side effects
   // on "this", by updating imprecise entries.
   inline HeapWord* forward_to_block_containing_addr(HeapWord* q,
                                                     const void* addr);
   // "q" is a block boundary that is <= "addr"; "n" is the address of the
   // next block (or the end of the space.)  Return the address of the
   // beginning of the block that contains "addr".  May have side effects
   // on "this", by updating imprecise entries.
   HeapWord* forward_to_block_containing_addr_slow(HeapWord* q,
                                                   HeapWord* n,
                                                   const void* addr);
   // Requires that "*threshold_" be the first array entry boundary at or
   // above "blk_start", and that "*index_" be the corresponding array
   // index.  If the block starts at or crosses "*threshold_", records
   // "blk_start" as the appropriate block start for the array index
   // starting at "*threshold_", and for any other indices crossed by the
   // block.  Updates "*threshold_" and "*index_" to correspond to the first
   // index after the block end.
   void alloc_block_work2(HeapWord** threshold_, size_t* index_,
                          HeapWord* blk_start, HeapWord* blk_end);
 public:
   // The space may not have it's bottom and top set yet, which is why the
   // region is passed as a parameter.  If "init_to_zero" is true, the
   // elements of the array are initialized to zero.  Otherwise, they are
   // initialized to point backwards to the beginning.
   G1BlockOffsetArray(G1BlockOffsetSharedArray* array, MemRegion mr,
                      bool init_to_zero);
   // Note: this ought to be part of the constructor, but that would require
   // "this" to be passed as a parameter to a member constructor for
   // the containing concrete subtype of Space.
   // This would be legal C++, but MS VC++ doesn't allow it.
   void set_space(Space* sp);
   // Resets the covered region to the given "mr".
   void set_region(MemRegion mr);
   // Resets the covered region to one with the same _bottom as before but
   // the "new_word_size".
   void resize(size_t new_word_size);
   // These must be guaranteed to work properly (i.e., do nothing)
   // when "blk_start" ("blk" for second version) is "NULL".
   virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
   virtual void alloc_block(HeapWord* blk, size_t size) {
     alloc_block(blk, blk + size);
   }
   // The following methods are useful and optimized for a
   // general, non-contiguous space.
   // Given a block [blk_start, blk_start + full_blk_size), and
   // a left_blk_size < full_blk_size, adjust the BOT to show two
   // blocks [blk_start, blk_start + left_blk_size) and
   // [blk_start + left_blk_size, blk_start + full_blk_size).
   // It is assumed (and verified in the non-product VM) that the
   // BOT was correct for the original block.
   void split_block(HeapWord* blk_start, size_t full_blk_size,
                            size_t left_blk_size);
   // Adjust the BOT to show that it has a single block in the
   // range [blk_start, blk_start + size). All necessary BOT
   // cards are adjusted, but _unallocated_block isn't.
   void single_block(HeapWord* blk_start, HeapWord* blk_end);
   void single_block(HeapWord* blk, size_t size) {
     single_block(blk, blk + size);
   }
   // Adjust BOT to show that it has a block in the range
   // [blk_start, blk_start + size). Only the first card
   // of BOT is touched. It is assumed (and verified in the
   // non-product VM) that the remaining cards of the block
   // are correct.
   void mark_block(HeapWord* blk_start, HeapWord* blk_end);
   void mark_block(HeapWord* blk, size_t size) {
     mark_block(blk, blk + size);
   }
   // Adjust _unallocated_block to indicate that a particular
   // block has been newly allocated or freed. It is assumed (and
   // verified in the non-product VM) that the BOT is correct for
   // the given block.
   inline void allocated(HeapWord* blk_start, HeapWord* blk_end) {
     // Verify that the BOT shows [blk, blk + blk_size) to be one block.
     verify_single_block(blk_start, blk_end);
     if (BlockOffsetArrayUseUnallocatedBlock) {
       _unallocated_block = MAX2(_unallocated_block, blk_end);
     }
   }
   inline void allocated(HeapWord* blk, size_t size) {
     allocated(blk, blk + size);
   }
   inline void freed(HeapWord* blk_start, HeapWord* blk_end);
   inline void freed(HeapWord* blk, size_t size);
   virtual HeapWord* block_start_unsafe(const void* addr);
   virtual HeapWord* block_start_unsafe_const(const void* addr) const;
   // Requires "addr" to be the start of a card and returns the
   // start of the block that contains the given address.
   HeapWord* block_start_careful(const void* addr) const;
   // If true, initialize array slots with no allocated blocks to zero.
   // Otherwise, make them point back to the front.
   bool init_to_zero() { return _init_to_zero; }
   // Verification & debugging - ensure that the offset table reflects the fact
   // that the block [blk_start, blk_end) or [blk, blk + size) is a
   // single block of storage. NOTE: can;t const this because of
   // call to non-const do_block_internal() below.
   inline void verify_single_block(HeapWord* blk_start, HeapWord* blk_end) {
     if (VerifyBlockOffsetArray) {
       do_block_internal(blk_start, blk_end, Action_check);
     }
   }
   inline void verify_single_block(HeapWord* blk, size_t size) {
     verify_single_block(blk, blk + size);
   }
   // Used by region verification. Checks that the contents of the
   // BOT reflect that there's a single object that spans the address
   // range [obj_start, obj_start + word_size); returns true if this is
   // the case, returns false if it's not.
   bool verify_for_object(HeapWord* obj_start, size_t word_size) const;
   // Verify that the given block is before _unallocated_block
   inline void verify_not_unallocated(HeapWord* blk_start,
                                      HeapWord* blk_end) const {
     if (BlockOffsetArrayUseUnallocatedBlock) {
       assert(blk_start < blk_end, "Block inconsistency?");
       assert(blk_end <= _unallocated_block, "_unallocated_block problem");
     }
   }
   inline void verify_not_unallocated(HeapWord* blk, size_t size) const {
     verify_not_unallocated(blk, blk + size);
   }
   void check_all_cards(size_t left_card, size_t right_card) const;
   virtual void print_on(outputStream* out) PRODUCT_RETURN;
 };
 // A subtype of BlockOffsetArray that takes advantage of the fact
 // that its underlying space is a ContiguousSpace, so that its "active"
 // region can be more efficiently tracked (than for a non-contiguous space).
 class G1BlockOffsetArrayContigSpace: public G1BlockOffsetArray {
   friend class VMStructs;
   // allocation boundary at which offset array must be updated
   HeapWord* _next_offset_threshold;
   size_t    _next_offset_index;      // index corresponding to that boundary
   // Work function to be called when allocation start crosses the next
   // threshold in the contig space.
   void alloc_block_work1(HeapWord* blk_start, HeapWord* blk_end) {
     alloc_block_work2(&_next_offset_threshold, &_next_offset_index,
                       blk_start, blk_end);
   }
  public:
   G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array, MemRegion mr);
   // Initialize the threshold to reflect the first boundary after the
   // bottom of the covered region.
   HeapWord* initialize_threshold();
   // Zero out the entry for _bottom (offset will be zero).
   void      zero_bottom_entry();
   // Return the next threshold, the point at which the table should be
   // updated.
   HeapWord* threshold() const { return _next_offset_threshold; }
   // These must be guaranteed to work properly (i.e., do nothing)
   // when "blk_start" ("blk" for second version) is "NULL".  In this
   // implementation, that's true because NULL is represented as 0, and thus
   // never exceeds the "_next_offset_threshold".
   void alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
     if (blk_end > _next_offset_threshold)
       alloc_block_work1(blk_start, blk_end);
   }
   void alloc_block(HeapWord* blk, size_t size) {
      alloc_block(blk, blk+size);
   }
   HeapWord* block_start_unsafe(const void* addr);
   HeapWord* block_start_unsafe_const(const void* addr) const;
   void set_for_starts_humongous(HeapWord* new_top);
   virtual void print_on(outputStream* out) PRODUCT_RETURN;
 };
 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp@2ace1c4ee8da (annotated)

src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp