jdk8-mips64-public/hotspot: comparison src/share/vm/memory/blockOffsetTable.hpp

--1:000000000000
+:f90c822e73f8
+/*
+* Copyright (c) 2000, 2012, 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_MEMORY_BLOCKOFFSETTABLE_HPP
+#define SHARE_VM_MEMORY_BLOCKOFFSETTABLE_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.
+//
+// BlockOffsetTable (abstract)
+//   - BlockOffsetArray (abstract)
+//     - BlockOffsetArrayNonContigSpace
+//     - BlockOffsetArrayContigSpace
+//
+class ContiguousSpace;
+//////////////////////////////////////////////////////////////////////////
+// The BlockOffsetTable "interface"
+//////////////////////////////////////////////////////////////////////////
+class BlockOffsetTable 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.
+BlockOffsetTable(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.
+virtual HeapWord* block_start_unsafe(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.
+HeapWord* block_start(const void* addr) const;
+};
+//////////////////////////////////////////////////////////////////////////
+// One implementation of "BlockOffsetTable," the BlockOffsetArray,
+// 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.  (Consider,
+// for example, the garbage-first generation.)
+// Here is the shared array type.
+//////////////////////////////////////////////////////////////////////////
+// BlockOffsetSharedArray
+//////////////////////////////////////////////////////////////////////////
+class BlockOffsetSharedArray: public CHeapObj<mtGC> {
+friend class BlockOffsetArray;
+friend class BlockOffsetArrayNonContigSpace;
+friend class BlockOffsetArrayContigSpace;
+friend class VMStructs;
+private:
+enum SomePrivateConstants {
+LogN = 9,
+LogN_words = LogN - LogHeapWordSize,
+N_bytes = 1 << LogN,
+N_words = 1 << LogN_words
+};
+bool _init_to_zero;
+// 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
+protected:
+// 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];
+}
+// An assertion-checking helper method for the set_offset_array() methods below.
+void check_reducing_assertion(bool reducing);
+void set_offset_array(size_t index, u_char offset, bool reducing = false) {
+check_reducing_assertion(reducing);
+assert(index < _vs.committed_size(), "index out of range");
+assert(!reducing || _offset_array[index] >= offset, "Not reducing");
+_offset_array[index] = offset;
+}
+void set_offset_array(size_t index, HeapWord* high, HeapWord* low, bool reducing = false) {
+check_reducing_assertion(reducing);
+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(!reducing || _offset_array[index] >=  (u_char)pointer_delta(high, low),
+"Not reducing");
+_offset_array[index] = (u_char)pointer_delta(high, low);
+}
+void set_offset_array(HeapWord* left, HeapWord* right, u_char offset, bool reducing = false) {
+check_reducing_assertion(reducing);
+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;
+// Below, we may use an explicit loop instead of memset()
+// because on certain platforms memset() can give concurrent
+// readers "out-of-thin-air," phantom zeros; see 6948537.
+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++) {
+// Elided until CR 6977974 is fixed properly.
+// assert(!reducing || _offset_array[i] >= offset, "Not reducing");
+_offset_array[i] = offset;
+}
+}
+}
+void set_offset_array(size_t left, size_t right, u_char offset, bool reducing = false) {
+check_reducing_assertion(reducing);
+assert(right < _vs.committed_size(), "right address out of range");
+assert(left  <= right, "indexes out of order");
+size_t num_cards = right - left + 1;
+// Below, we may use an explicit loop instead of memset
+// because on certain platforms memset() can give concurrent
+// readers "out-of-thin-air," phantom zeros; see 6948537.
+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++) {
+// Elided until CR 6977974 is fixed properly.
+// assert(!reducing || _offset_array[i] >= offset, "Not reducing");
+_offset_array[i] = offset;
+}
+}
+}
+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::allocation_align_size_up(number_of_slots);
+}
+public:
+// 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
+// BlockOffsetTable(s) to initialize cards.
+BlockOffsetSharedArray(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);
+// Whether entries should be initialized to zero. Used currently only for
+// error checking.
+void set_init_to_zero(bool val) { _init_to_zero = val; }
+bool init_to_zero() { return _init_to_zero; }
+// Updates all the BlockOffsetArray's sharing this shared array to
+// reflect the current "top"'s of their spaces.
+void update_offset_arrays();   // Not yet implemented!
+// Return the appropriate index into "_offset_array" for "p".
+size_t index_for(const void* p) const;
+// Return the address indicating the start of the region corresponding to
+// "index" in "_offset_array".
+HeapWord* address_for_index(size_t index) const;
+// Return the address "p" incremented by the size of
+// a region.  This method does not align the address
+// returned to the start of a region.  It is a simple
+// primitive.
+HeapWord* inc_by_region_size(HeapWord* p) const { return p + N_words; }
+};
+//////////////////////////////////////////////////////////////////////////
+// The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray.
+//////////////////////////////////////////////////////////////////////////
+class BlockOffsetArray: public BlockOffsetTable {
+friend class VMStructs;
+friend class G1BlockOffsetArray; // temp. until we restructure and cleanup
+protected:
+// The following enums are used by do_block_internal() below
+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()).
+};
+enum SomePrivateConstants {
+N_words = BlockOffsetSharedArray::N_words,
+LogN    = BlockOffsetSharedArray::LogN,
+// entries "e" of at least N_words mean "go back by Base^(e-N_words)."
+// All entries are less than "N_words + N_powers".
+LogBase = 4,
+Base = (1 << LogBase),
+N_powers = 14
+};
+static size_t power_to_cards_back(uint i) {
+return (size_t)1 << (LogBase * i);
+}
+static size_t power_to_words_back(uint i) {
+return power_to_cards_back(i) * N_words;
+}
+static size_t entry_to_cards_back(u_char entry) {
+assert(entry >= N_words, "Precondition");
+return power_to_cards_back(entry - N_words);
+}
+static size_t entry_to_words_back(u_char entry) {
+assert(entry >= N_words, "Precondition");
+return power_to_words_back(entry - N_words);
+}
+// The shared array, which is shared with other BlockOffsetArray's
+// corresponding to different spaces within a generation or span of
+// memory.
+BlockOffsetSharedArray* _array;
+// The space that owns this subregion.
+Space* _sp;
+// 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;
+// An assertion-checking helper method for the set_remainder*() methods below.
+void check_reducing_assertion(bool reducing) { _array->check_reducing_assertion(reducing); }
+// 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. The last parameter, reducing, indicates whether the
+// updates to individual entries always reduce the entry from a higher
+// to a lower value. (For example this would hold true during a temporal
+// regime during which only block splits were updating the BOT.
+void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing = false);
+// 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, bool reducing = false);
+// A helper function for BOT adjustment/verification work
+void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action, bool reducing = false);
+public:
+// The space may not have its 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.
+BlockOffsetArray(BlockOffsetSharedArray* 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) { _sp = sp; }
+// Resets the covered region to the given "mr".
+void set_region(MemRegion mr) {
+_bottom = mr.start();
+_end = mr.end();
+}
+// 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) {
+HeapWord* new_end = _bottom + new_word_size;
+if (_end < new_end && !init_to_zero()) {
+// verify that the old and new boundaries are also card boundaries
+assert(_array->is_card_boundary(_end),
+"_end not a card boundary");
+assert(_array->is_card_boundary(new_end),
+"new _end would not be a card boundary");
+// set all the newly added cards
+_array->set_offset_array(_end, new_end, N_words);
+}
+_end = new_end;  // update _end
+}
+// 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);
+}
+// When the alloc_block() call returns, the block offset table should
+// have enough information such that any subsequent block_start() call
+// with an argument equal to an address that is within the range
+// [blk_start, blk_end) would return the value blk_start, provided
+// there have been no calls in between that reset this information
+// (e.g. see BlockOffsetArrayNonContigSpace::single_block() call
+// for an appropriate range covering the said interval).
+// These methods expect to be called with [blk_start, blk_end)
+// representing a block of memory in the heap.
+virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
+void alloc_block(HeapWord* blk, size_t size) {
+alloc_block(blk, blk + size);
+}
+// 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; }
+// Corresponding setter
+void set_init_to_zero(bool val) {
+_init_to_zero = val;
+assert(_array != NULL, "_array should be non-NULL");
+_array->set_init_to_zero(val);
+}
+// Debugging
+// Return the index of the last entry in the "active" region.
+virtual size_t last_active_index() const = 0;
+// Verify the block offset table
+void verify() const;
+void check_all_cards(size_t left_card, size_t right_card) const;
+};
+////////////////////////////////////////////////////////////////////////////
+// A subtype of BlockOffsetArray that takes advantage of the fact
+// that its underlying space is a NonContiguousSpace, so that some
+// specialized interfaces can be made available for spaces that
+// manipulate the table.
+////////////////////////////////////////////////////////////////////////////
+class BlockOffsetArrayNonContigSpace: public BlockOffsetArray {
+friend class VMStructs;
+private:
+// 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;
+public:
+BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
+BlockOffsetArray(array, mr, false),
+_unallocated_block(_bottom) { }
+// accessor
+HeapWord* unallocated_block() const {
+assert(BlockOffsetArrayUseUnallocatedBlock,
+"_unallocated_block is not being maintained");
+return _unallocated_block;
+}
+void set_unallocated_block(HeapWord* block) {
+assert(BlockOffsetArrayUseUnallocatedBlock,
+"_unallocated_block is not being maintained");
+assert(block >= _bottom && block <= _end, "out of range");
+_unallocated_block = block;
+}
+// These methods expect to be called with [blk_start, blk_end)
+// representing a block of memory in the heap.
+void alloc_block(HeapWord* blk_start, HeapWord* blk_end);
+void alloc_block(HeapWord* blk, size_t size) {
+alloc_block(blk, blk + size);
+}
+// The following methods are useful and optimized for a
+// 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 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, bool reducing = false);
+void mark_block(HeapWord* blk, size_t size, bool reducing = false) {
+mark_block(blk, blk + size, reducing);
+}
+// 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.
+void allocated(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false) {
+// 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);
+}
+}
+void allocated(HeapWord* blk, size_t size, bool reducing = false) {
+allocated(blk, blk + size, reducing);
+}
+void freed(HeapWord* blk_start, HeapWord* blk_end);
+void freed(HeapWord* blk, size_t size);
+HeapWord* block_start_unsafe(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;
+// 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.
+void verify_single_block(HeapWord* blk_start, HeapWord* blk_end)
+PRODUCT_RETURN;
+void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN;
+// Verify that the given block is before _unallocated_block
+void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end)
+const PRODUCT_RETURN;
+void verify_not_unallocated(HeapWord* blk, size_t size)
+const PRODUCT_RETURN;
+// Debugging support
+virtual size_t last_active_index() const;
+};
+////////////////////////////////////////////////////////////////////////////
+// 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 BlockOffsetArrayContigSpace: public BlockOffsetArray {
+friend class VMStructs;
+private:
+// 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 when allocation start crosses threshold.
+void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end);
+public:
+BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr):
+BlockOffsetArray(array, mr, true) {
+_next_offset_threshold = NULL;
+_next_offset_index = 0;
+}
+void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); }
+// Initialize the threshold for an empty heap.
+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; }
+// In general, these methods expect to be called with
+// [blk_start, blk_end) representing a block of memory in the heap.
+// In this implementation, however, we are OK even if blk_start and/or
+// blk_end are NULL 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_work(blk_start, blk_end);
+}
+}
+void alloc_block(HeapWord* blk, size_t size) {
+alloc_block(blk, blk + size);
+}
+HeapWord* block_start_unsafe(const void* addr) const;
+// Debugging support
+virtual size_t last_active_index() const;
+};
+#endif // SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP

Mercurial > jdk8-mips64-public > hotspot / file comparison

comparison: src/share/vm/memory/blockOffsetTable.hpp

src/share/vm/memory/blockOffsetTable.hpp