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8055816: Remove dead code in g1BlockOffsetTable

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Reviewed-by: tschatzl, mgerdin
This commit is contained in:
Bengt Rutisson 2014-08-27 10:51:08 +02:00
parent 9086b5795f
commit bbe82cb85b
5 changed files with 13 additions and 374 deletions
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182
hotspot/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.cpp
View file

@ -32,13 +32,6 @@
void G1BlockOffsetSharedArrayMappingChangedListener::on_commit(uint start_idx, size_t num_regions) {
// Nothing to do. The BOT is hard-wired to be part of the HeapRegion, and we cannot
// retrieve it here since this would cause firing of several asserts. The code
// executed after commit of a region already needs to do some re-initialization of
// the HeapRegion, so we combine that.
}
//////////////////////////////////////////////////////////////////////
// G1BlockOffsetSharedArray
//////////////////////////////////////////////////////////////////////
@ -72,26 +65,16 @@ bool G1BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const {
return (delta & right_n_bits(LogN_words)) == (size_t)NoBits;
}
void G1BlockOffsetSharedArray::set_offset_array(HeapWord* left, HeapWord* right, u_char offset) {
set_offset_array(index_for(left), index_for(right -1), offset);
}
//////////////////////////////////////////////////////////////////////
// G1BlockOffsetArray
//////////////////////////////////////////////////////////////////////
G1BlockOffsetArray::G1BlockOffsetArray(G1BlockOffsetSharedArray* array,
MemRegion mr, bool init_to_zero) :
MemRegion mr) :
G1BlockOffsetTable(mr.start(), mr.end()),
_unallocated_block(_bottom),
_array(array), _gsp(NULL),
_init_to_zero(init_to_zero) {
_array(array), _gsp(NULL) {
assert(_bottom <= _end, "arguments out of order");
if (!_init_to_zero) {
// initialize cards to point back to mr.start()
set_remainder_to_point_to_start(mr.start() + N_words, mr.end());
_array->set_offset_array(0, 0); // set first card to 0
}
}
void G1BlockOffsetArray::set_space(G1OffsetTableContigSpace* sp) {
@ -181,93 +164,6 @@ G1BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size
DEBUG_ONLY(check_all_cards(start_card, end_card);)
}
// The block [blk_start, blk_end) has been allocated;
// adjust the block offset table to represent this information;
// right-open interval: [blk_start, blk_end)
void
G1BlockOffsetArray::alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
mark_block(blk_start, blk_end);
allocated(blk_start, blk_end);
}
// Adjust BOT to show that a previously whole block has been split
// into two.
void G1BlockOffsetArray::split_block(HeapWord* blk, size_t blk_size,
size_t left_blk_size) {
// Verify that the BOT shows [blk, blk + blk_size) to be one block.
verify_single_block(blk, blk_size);
// Update the BOT to indicate that [blk + left_blk_size, blk + blk_size)
// is one single block.
mark_block(blk + left_blk_size, blk + blk_size);
}
// Action_mark - update the BOT for the block [blk_start, blk_end).
// Current typical use is for splitting a block.
// Action_single - update the BOT for an allocation.
// Action_verify - BOT verification.
void G1BlockOffsetArray::do_block_internal(HeapWord* blk_start,
HeapWord* blk_end,
Action action) {
assert(Universe::heap()->is_in_reserved(blk_start),
"reference must be into the heap");
assert(Universe::heap()->is_in_reserved(blk_end-1),
"limit must be within the heap");
// This is optimized to make the test fast, assuming we only rarely
// cross boundaries.
uintptr_t end_ui = (uintptr_t)(blk_end - 1);
uintptr_t start_ui = (uintptr_t)blk_start;
// Calculate the last card boundary preceding end of blk
intptr_t boundary_before_end = (intptr_t)end_ui;
clear_bits(boundary_before_end, right_n_bits(LogN));
if (start_ui <= (uintptr_t)boundary_before_end) {
// blk starts at or crosses a boundary
// Calculate index of card on which blk begins
size_t start_index = _array->index_for(blk_start);
// Index of card on which blk ends
size_t end_index = _array->index_for(blk_end - 1);
// Start address of card on which blk begins
HeapWord* boundary = _array->address_for_index(start_index);
assert(boundary <= blk_start, "blk should start at or after boundary");
if (blk_start != boundary) {
// blk starts strictly after boundary
// adjust card boundary and start_index forward to next card
boundary += N_words;
start_index++;
}
assert(start_index <= end_index, "monotonicity of index_for()");
assert(boundary <= (HeapWord*)boundary_before_end, "tautology");
switch (action) {
case Action_mark: {
if (init_to_zero()) {
_array->set_offset_array(start_index, boundary, blk_start);
break;
} // Else fall through to the next case
}
case Action_single: {
_array->set_offset_array(start_index, boundary, blk_start);
// We have finished marking the "offset card". We need to now
// mark the subsequent cards that this blk spans.
if (start_index < end_index) {
HeapWord* rem_st = _array->address_for_index(start_index) + N_words;
HeapWord* rem_end = _array->address_for_index(end_index) + N_words;
set_remainder_to_point_to_start(rem_st, rem_end);
}
break;
}
case Action_check: {
_array->check_offset_array(start_index, boundary, blk_start);
// We have finished checking the "offset card". We need to now
// check the subsequent cards that this blk spans.
check_all_cards(start_index + 1, end_index);
break;
}
default:
ShouldNotReachHere();
}
}
}
// The card-interval [start_card, end_card] is a closed interval; this
// is an expensive check -- use with care and only under protection of
// suitable flag.
@ -306,25 +202,6 @@ void G1BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) con
}
}
// The range [blk_start, blk_end) represents a single contiguous block
// of storage; modify the block offset table to represent this
// information; Right-open interval: [blk_start, blk_end)
// NOTE: this method does _not_ adjust _unallocated_block.
void
G1BlockOffsetArray::single_block(HeapWord* blk_start, HeapWord* blk_end) {
do_block_internal(blk_start, blk_end, Action_single);
}
// Mark the BOT such that if [blk_start, blk_end) straddles a card
// boundary, the card following the first such boundary is marked
// with the appropriate offset.
// NOTE: this method does _not_ adjust _unallocated_block or
// any cards subsequent to the first one.
void
G1BlockOffsetArray::mark_block(HeapWord* blk_start, HeapWord* blk_end) {
do_block_internal(blk_start, blk_end, Action_mark);
}
HeapWord* G1BlockOffsetArray::block_start_unsafe(const void* addr) {
assert(_bottom <= addr && addr < _end,
"addr must be covered by this Array");
@ -397,57 +274,13 @@ G1BlockOffsetArray::forward_to_block_containing_addr_slow(HeapWord* q,
return forward_to_block_containing_addr_const(q, n, addr);
}
HeapWord* G1BlockOffsetArray::block_start_careful(const void* addr) const {
assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
assert(_bottom <= addr && addr < _end,
"addr must be covered by this Array");
// Must read this exactly once because it can be modified by parallel
// allocation.
HeapWord* ub = _unallocated_block;
if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
assert(ub < _end, "tautology (see above)");
return ub;
}
// Otherwise, find the block start using the table, but taking
// care (cf block_start_unsafe() above) not to parse any objects/blocks
// on the cards themselves.
size_t index = _array->index_for(addr);
assert(_array->address_for_index(index) == addr,
"arg should be start of card");
HeapWord* q = (HeapWord*)addr;
uint offset;
do {
offset = _array->offset_array(index--);
q -= offset;
} while (offset == N_words);
assert(q <= addr, "block start should be to left of arg");
return q;
}
// Note that the committed size of the covered space may have changed,
// so the table size might also wish to change.
void G1BlockOffsetArray::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
}
void G1BlockOffsetArray::set_region(MemRegion mr) {
_bottom = mr.start();
_end = mr.end();
}
//
// threshold_
// | _index_
@ -606,7 +439,7 @@ block_start_unsafe_const(const void* addr) const {
G1BlockOffsetArrayContigSpace::
G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array,
MemRegion mr) :
G1BlockOffsetArray(array, mr, true)
G1BlockOffsetArray(array, mr)
{
_next_offset_threshold = NULL;
_next_offset_index = 0;
@ -641,15 +474,6 @@ HeapWord* G1BlockOffsetArrayContigSpace::initialize_threshold() {
return _next_offset_threshold;
}
void G1BlockOffsetArrayContigSpace::zero_bottom_entry() {
assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
"just checking");
size_t bottom_index = _array->index_for(_bottom);
assert(_array->address_for_index(bottom_index) == _bottom,
"Precondition of call");
_array->set_offset_array(bottom_index, 0);
}
void
G1BlockOffsetArrayContigSpace::set_for_starts_humongous(HeapWord* new_top) {
assert(new_top <= _end, "_end should have already been updated");

135
hotspot/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.hpp
View file

@ -109,7 +109,12 @@ public:
class G1BlockOffsetSharedArrayMappingChangedListener : public G1MappingChangedListener {
public:
virtual void on_commit(uint start_idx, size_t num_regions);
virtual void on_commit(uint start_idx, size_t num_regions) {
// Nothing to do. The BOT is hard-wired to be part of the HeapRegion, and we cannot
// retrieve it here since this would cause firing of several asserts. The code
// executed after commit of a region already needs to do some re-initialization of
// the HeapRegion, so we combine that.
}
};
// This implementation of "G1BlockOffsetTable" divides the covered region
@ -153,8 +158,6 @@ private:
// For performance these have to devolve to array accesses in product builds.
inline u_char offset_array(size_t index) const;
void set_offset_array(HeapWord* left, HeapWord* right, u_char offset);
void set_offset_array_raw(size_t index, u_char offset) {
_offset_array[index] = offset;
}
@ -165,8 +168,6 @@ private:
inline void set_offset_array(size_t left, size_t right, u_char offset);
inline void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const;
bool is_card_boundary(HeapWord* p) const;
public:
@ -193,8 +194,6 @@ public:
// G1BlockOffsetTable(s) to initialize cards.
G1BlockOffsetSharedArray(MemRegion heap, G1RegionToSpaceMapper* storage);
void set_bottom(HeapWord* new_bottom);
// Return the appropriate index into "_offset_array" for "p".
inline size_t index_for(const void* p) const;
inline size_t index_for_raw(const void* p) const;
@ -220,14 +219,6 @@ private:
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;
@ -235,10 +226,6 @@ private:
// The space that owns this subregion.
G1OffsetTableContigSpace* _gsp;
// 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.
@ -253,9 +240,6 @@ private:
// 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:
G1OffsetTableContigSpace* gsp() const { return _gsp; }
@ -303,11 +287,9 @@ protected:
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);
// region is passed as a parameter. The elements of the array are
// initialized to zero.
G1BlockOffsetArray(G1BlockOffsetSharedArray* array, MemRegion mr);
// 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
@ -315,114 +297,19 @@ public:
// This would be legal C++, but MS VC++ doesn't allow it.
void set_space(G1OffsetTableContigSpace* 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;
@ -445,14 +332,12 @@ class G1BlockOffsetArrayContigSpace: public G1BlockOffsetArray {
blk_start, blk_end);
}
// Variant of zero_bottom_entry that does not check for availability of the
// Zero out the entry for _bottom (offset will be zero). Does not check for availability of the
// memory first.
void zero_bottom_entry_raw();
// Variant of initialize_threshold that does not check for availability of the
// memory first.
HeapWord* initialize_threshold_raw();
// Zero out the entry for _bottom (offset will be zero).
void zero_bottom_entry();
public:
G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array, MemRegion mr);

31
hotspot/src/share/vm/gc_implementation/g1/g1BlockOffsetTable.inline.hpp
View file

@ -91,13 +91,6 @@ void G1BlockOffsetSharedArray::set_offset_array(size_t left, size_t right, u_cha
}
}
void G1BlockOffsetSharedArray::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");
}
// Variant of index_for that does not check the index for validity.
inline size_t G1BlockOffsetSharedArray::index_for_raw(const void* p) const {
return pointer_delta((char*)p, _reserved.start(), sizeof(char)) >> LogN;
@ -193,28 +186,4 @@ G1BlockOffsetArray::forward_to_block_containing_addr(HeapWord* q,
return q;
}
//////////////////////////////////////////////////////////////////////////
// BlockOffsetArrayNonContigSpace inlines
//////////////////////////////////////////////////////////////////////////
inline void G1BlockOffsetArray::freed(HeapWord* blk_start, HeapWord* blk_end) {
// Verify that the BOT shows [blk_start, blk_end) to be one block.
verify_single_block(blk_start, blk_end);
// adjust _unallocated_block upward or downward
// as appropriate
if (BlockOffsetArrayUseUnallocatedBlock) {
assert(_unallocated_block <= _end,
"Inconsistent value for _unallocated_block");
if (blk_end >= _unallocated_block && blk_start <= _unallocated_block) {
// CMS-specific note: a block abutting _unallocated_block to
// its left is being freed, a new block is being added or
// we are resetting following a compaction
_unallocated_block = blk_start;
}
}
}
inline void G1BlockOffsetArray::freed(HeapWord* blk, size_t size) {
freed(blk, blk + size);
}
#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1BLOCKOFFSETTABLE_INLINE_HPP

23
hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp
View file

@ -322,29 +322,6 @@ bool HeapRegion::claimHeapRegion(jint claimValue) {
return false;
}
HeapWord* HeapRegion::next_block_start_careful(HeapWord* addr) {
HeapWord* low = addr;
HeapWord* high = end();
while (low < high) {
size_t diff = pointer_delta(high, low);
// Must add one below to bias toward the high amount. Otherwise, if
// "high" were at the desired value, and "low" were one less, we
// would not converge on "high". This is not symmetric, because
// we set "high" to a block start, which might be the right one,
// which we don't do for "low".
HeapWord* middle = low + (diff+1)/2;
if (middle == high) return high;
HeapWord* mid_bs = block_start_careful(middle);
if (mid_bs < addr) {
low = middle;
} else {
high = mid_bs;
}
}
assert(low == high && low >= addr, "Didn't work.");
return low;
}
HeapRegion::HeapRegion(uint hrm_index,
G1BlockOffsetSharedArray* sharedOffsetArray,
MemRegion mr) :

16
hotspot/src/share/vm/gc_implementation/g1/heapRegion.hpp
View file

@ -206,10 +206,6 @@ class G1OffsetTableContigSpace: public CompactibleSpace {
_offsets.reset_bot();
}
void update_bot_for_object(HeapWord* start, size_t word_size) {
_offsets.alloc_block(start, word_size);
}
void print_bot_on(outputStream* out) {
_offsets.print_on(out);
}
@ -737,18 +733,6 @@ class HeapRegion: public G1OffsetTableContigSpace {
bool filter_young,
jbyte* card_ptr);
// A version of block start that is guaranteed to find *some* block
// boundary at or before "p", but does not object iteration, and may
// therefore be used safely when the heap is unparseable.
HeapWord* block_start_careful(const void* p) const {
return _offsets.block_start_careful(p);
}
// Requires that "addr" is within the region. Returns the start of the
// first ("careful") block that starts at or after "addr", or else the
// "end" of the region if there is no such block.
HeapWord* next_block_start_careful(HeapWord* addr);
size_t recorded_rs_length() const { return _recorded_rs_length; }
double predicted_elapsed_time_ms() const { return _predicted_elapsed_time_ms; }
size_t predicted_bytes_to_copy() const { return _predicted_bytes_to_copy; }