jdk8-mips64-public/hotspot: comparison src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp

--1:000000000000
+:f90c822e73f8
+/*
+* Copyright (c) 2001, 2014, 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,
+err_msg("new_bottom (" PTR_FORMAT ") > _end (" PTR_FORMAT ")",
+p2i(new_bottom), p2i(_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<mtGC> {
+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
+void check_index(size_t index, const char* msg) const {
+assert(index < _vs.committed_size(),
+err_msg("%s - "
+"index: " SIZE_FORMAT ", _vs.committed_size: " SIZE_FORMAT,
+msg, index, _vs.committed_size()));
+}
+void check_offset(size_t offset, const char* msg) const {
+assert(offset <= N_words,
+err_msg("%s - "
+"offset: " SIZE_FORMAT ", N_words: " UINT32_FORMAT,
+msg, offset, N_words));
+}
+// Bounds checking accessors:
+// For performance these have to devolve to array accesses in product builds.
+u_char offset_array(size_t index) const {
+check_index(index, "index out of range");
+return _offset_array[index];
+}
+void set_offset_array(size_t index, u_char offset) {
+check_index(index, "index out of range");
+check_offset(offset, "offset too large");
+_offset_array[index] = offset;
+}
+void set_offset_array(size_t index, HeapWord* high, HeapWord* low) {
+check_index(index, "index out of range");
+assert(high >= low, "addresses out of order");
+check_offset(pointer_delta(high, low), "offset too large");
+_offset_array[index] = (u_char) pointer_delta(high, low);
+}
+void set_offset_array(HeapWord* left, HeapWord* right, u_char offset) {
+check_index(index_for(right - 1), "right address out of range");
+assert(left  < right, "Heap addresses out of order");
+size_t num_cards = pointer_delta(right, left) >> LogN_words;
+if (UseMemSetInBOT) {
+memset(&_offset_array[index_for(left)], offset, num_cards);
+} else {
+size_t i = index_for(left);
+const size_t end = i + num_cards;
+for (; i < end; i++) {
+_offset_array[i] = offset;
+}
+}
+}
+void set_offset_array(size_t left, size_t right, u_char offset) {
+check_index(right, "right index out of range");
+assert(left <= right, "indexes out of order");
+size_t num_cards = right - left + 1;
+if (UseMemSetInBOT) {
+memset(&_offset_array[left], offset, num_cards);
+} else {
+size_t i = left;
+const size_t end = i + num_cards;
+for (; i < end; i++) {
+_offset_array[i] = offset;
+}
+}
+}
+void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {
+check_index(index, "index out of range");
+assert(high >= low, "addresses out of order");
+check_offset(pointer_delta(high, low), "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 / file comparison

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

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