--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/g1BlockOffsetTable.cpp Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,429 @@
+/*
+ * Copyright (c) 2001, 2017, 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.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc/g1/g1BlockOffsetTable.inline.hpp"
+#include "gc/g1/g1CollectedHeap.inline.hpp"
+#include "gc/g1/heapRegion.hpp"
+#include "gc/shared/space.hpp"
+#include "logging/log.hpp"
+#include "oops/oop.inline.hpp"
+#include "runtime/java.hpp"
+#include "services/memTracker.hpp"
+
+
+
+//////////////////////////////////////////////////////////////////////
+// G1BlockOffsetTable
+//////////////////////////////////////////////////////////////////////
+
+G1BlockOffsetTable::G1BlockOffsetTable(MemRegion heap, G1RegionToSpaceMapper* storage) :
+ _reserved(heap), _offset_array(NULL) {
+
+ MemRegion bot_reserved = storage->reserved();
+
+ _offset_array = (u_char*)bot_reserved.start();
+
+ log_trace(gc, bot)("G1BlockOffsetTable::G1BlockOffsetTable: ");
+ log_trace(gc, bot)(" rs.base(): " PTR_FORMAT " rs.size(): " SIZE_FORMAT " rs end(): " PTR_FORMAT,
+ p2i(bot_reserved.start()), bot_reserved.byte_size(), p2i(bot_reserved.end()));
+}
+
+bool G1BlockOffsetTable::is_card_boundary(HeapWord* p) const {
+ assert(p >= _reserved.start(), "just checking");
+ size_t delta = pointer_delta(p, _reserved.start());
+ return (delta & right_n_bits((int)BOTConstants::LogN_words)) == (size_t)NoBits;
+}
+
+#ifdef ASSERT
+void G1BlockOffsetTable::check_index(size_t index, const char* msg) const {
+ assert((index) < (_reserved.word_size() >> BOTConstants::LogN_words),
+ "%s - index: " SIZE_FORMAT ", _vs.committed_size: " SIZE_FORMAT,
+ msg, (index), (_reserved.word_size() >> BOTConstants::LogN_words));
+ assert(G1CollectedHeap::heap()->is_in_exact(address_for_index_raw(index)),
+ "Index " SIZE_FORMAT " corresponding to " PTR_FORMAT
+ " (%u) is not in committed area.",
+ (index),
+ p2i(address_for_index_raw(index)),
+ G1CollectedHeap::heap()->addr_to_region(address_for_index_raw(index)));
+}
+#endif // ASSERT
+
+//////////////////////////////////////////////////////////////////////
+// G1BlockOffsetTablePart
+//////////////////////////////////////////////////////////////////////
+
+G1BlockOffsetTablePart::G1BlockOffsetTablePart(G1BlockOffsetTable* array, G1ContiguousSpace* gsp) :
+ _bot(array),
+ _space(gsp),
+ _next_offset_threshold(NULL),
+ _next_offset_index(0)
+{
+ debug_only(_object_can_span = false;)
+}
+
+// The arguments follow the normal convention of denoting
+// a right-open interval: [start, end)
+void G1BlockOffsetTablePart:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end) {
+
+ if (start >= end) {
+ // The start address is equal to the end address (or to
+ // the right of the end address) so there are not cards
+ // that need to be updated..
+ return;
+ }
+
+ // Write the backskip value for each region.
+ //
+ // offset
+ // card 2nd 3rd
+ // | +- 1st | |
+ // v v v v
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
+ // |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ...
+ // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-
+ // 11 19 75
+ // 12
+ //
+ // offset card is the card that points to the start of an object
+ // x - offset value of offset card
+ // 1st - start of first logarithmic region
+ // 0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1
+ // 2nd - start of second logarithmic region
+ // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8
+ // 3rd - start of third logarithmic region
+ // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64
+ //
+ // integer below the block offset entry is an example of
+ // the index of the entry
+ //
+ // Given an address,
+ // Find the index for the address
+ // Find the block offset table entry
+ // Convert the entry to a back slide
+ // (e.g., with today's, offset = 0x81 =>
+ // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8
+ // Move back N (e.g., 8) entries and repeat with the
+ // value of the new entry
+ //
+ size_t start_card = _bot->index_for(start);
+ size_t end_card = _bot->index_for(end-1);
+ assert(start ==_bot->address_for_index(start_card), "Precondition");
+ assert(end ==_bot->address_for_index(end_card)+BOTConstants::N_words, "Precondition");
+ set_remainder_to_point_to_start_incl(start_card, end_card); // closed interval
+}
+
+// Unlike the normal convention in this code, the argument here denotes
+// a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
+// above.
+void G1BlockOffsetTablePart::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) {
+ if (start_card > end_card) {
+ return;
+ }
+ assert(start_card > _bot->index_for(_space->bottom()), "Cannot be first card");
+ assert(_bot->offset_array(start_card-1) <= BOTConstants::N_words,
+ "Offset card has an unexpected value");
+ size_t start_card_for_region = start_card;
+ u_char offset = max_jubyte;
+ for (uint i = 0; i < BOTConstants::N_powers; i++) {
+ // -1 so that the the card with the actual offset is counted. Another -1
+ // so that the reach ends in this region and not at the start
+ // of the next.
+ size_t reach = start_card - 1 + (BOTConstants::power_to_cards_back(i+1) - 1);
+ offset = BOTConstants::N_words + i;
+ if (reach >= end_card) {
+ _bot->set_offset_array(start_card_for_region, end_card, offset);
+ start_card_for_region = reach + 1;
+ break;
+ }
+ _bot->set_offset_array(start_card_for_region, reach, offset);
+ start_card_for_region = reach + 1;
+ }
+ assert(start_card_for_region > end_card, "Sanity check");
+ DEBUG_ONLY(check_all_cards(start_card, end_card);)
+}
+
+// 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.
+void G1BlockOffsetTablePart::check_all_cards(size_t start_card, size_t end_card) const {
+
+ if (end_card < start_card) {
+ return;
+ }
+ guarantee(_bot->offset_array(start_card) == BOTConstants::N_words, "Wrong value in second card");
+ for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
+ u_char entry = _bot->offset_array(c);
+ if (c - start_card > BOTConstants::power_to_cards_back(1)) {
+ guarantee(entry > BOTConstants::N_words,
+ "Should be in logarithmic region - "
+ "entry: %u, "
+ "_array->offset_array(c): %u, "
+ "N_words: %u",
+ (uint)entry, (uint)_bot->offset_array(c), BOTConstants::N_words);
+ }
+ size_t backskip = BOTConstants::entry_to_cards_back(entry);
+ size_t landing_card = c - backskip;
+ guarantee(landing_card >= (start_card - 1), "Inv");
+ if (landing_card >= start_card) {
+ guarantee(_bot->offset_array(landing_card) <= entry,
+ "Monotonicity - landing_card offset: %u, "
+ "entry: %u",
+ (uint)_bot->offset_array(landing_card), (uint)entry);
+ } else {
+ guarantee(landing_card == start_card - 1, "Tautology");
+ // Note that N_words is the maximum offset value
+ guarantee(_bot->offset_array(landing_card) <= BOTConstants::N_words,
+ "landing card offset: %u, "
+ "N_words: %u",
+ (uint)_bot->offset_array(landing_card), (uint)BOTConstants::N_words);
+ }
+ }
+}
+
+HeapWord* G1BlockOffsetTablePart::forward_to_block_containing_addr_slow(HeapWord* q,
+ HeapWord* n,
+ const void* addr) {
+ // We're not in the normal case. We need to handle an important subcase
+ // here: LAB allocation. An allocation previously recorded in the
+ // offset table was actually a lab allocation, and was divided into
+ // several objects subsequently. Fix this situation as we answer the
+ // query, by updating entries as we cross them.
+
+ // If the fist object's end q is at the card boundary. Start refining
+ // with the corresponding card (the value of the entry will be basically
+ // set to 0). If the object crosses the boundary -- start from the next card.
+ size_t n_index = _bot->index_for(n);
+ size_t next_index = _bot->index_for(n) + !_bot->is_card_boundary(n);
+ // Calculate a consistent next boundary. If "n" is not at the boundary
+ // already, step to the boundary.
+ HeapWord* next_boundary = _bot->address_for_index(n_index) +
+ (n_index == next_index ? 0 : BOTConstants::N_words);
+ assert(next_boundary <= _bot->_reserved.end(),
+ "next_boundary is beyond the end of the covered region "
+ " next_boundary " PTR_FORMAT " _array->_end " PTR_FORMAT,
+ p2i(next_boundary), p2i(_bot->_reserved.end()));
+ if (addr >= _space->top()) return _space->top();
+ while (next_boundary < addr) {
+ while (n <= next_boundary) {
+ q = n;
+ oop obj = oop(q);
+ if (obj->klass_or_null_acquire() == NULL) return q;
+ n += block_size(q);
+ }
+ assert(q <= next_boundary && n > next_boundary, "Consequence of loop");
+ // [q, n) is the block that crosses the boundary.
+ alloc_block_work(&next_boundary, &next_index, q, n);
+ }
+ return forward_to_block_containing_addr_const(q, n, addr);
+}
+
+//
+// threshold_
+// | _index_
+// v v
+// +-------+-------+-------+-------+-------+
+// | i-1 | i | i+1 | i+2 | i+3 |
+// +-------+-------+-------+-------+-------+
+// ( ^ ]
+// block-start
+//
+void G1BlockOffsetTablePart::alloc_block_work(HeapWord** threshold_, size_t* index_,
+ HeapWord* blk_start, HeapWord* blk_end) {
+ // For efficiency, do copy-in/copy-out.
+ HeapWord* threshold = *threshold_;
+ size_t index = *index_;
+
+ assert(blk_start != NULL && blk_end > blk_start,
+ "phantom block");
+ assert(blk_end > threshold, "should be past threshold");
+ assert(blk_start <= threshold, "blk_start should be at or before threshold");
+ assert(pointer_delta(threshold, blk_start) <= BOTConstants::N_words,
+ "offset should be <= BlockOffsetSharedArray::N");
+ assert(G1CollectedHeap::heap()->is_in_reserved(blk_start),
+ "reference must be into the heap");
+ assert(G1CollectedHeap::heap()->is_in_reserved(blk_end-1),
+ "limit must be within the heap");
+ assert(threshold == _bot->_reserved.start() + index*BOTConstants::N_words,
+ "index must agree with threshold");
+
+ DEBUG_ONLY(size_t orig_index = index;)
+
+ // Mark the card that holds the offset into the block. Note
+ // that _next_offset_index and _next_offset_threshold are not
+ // updated until the end of this method.
+ _bot->set_offset_array(index, threshold, blk_start);
+
+ // We need to now mark the subsequent cards that this blk spans.
+
+ // Index of card on which blk ends.
+ size_t end_index = _bot->index_for(blk_end - 1);
+
+ // Are there more cards left to be updated?
+ if (index + 1 <= end_index) {
+ HeapWord* rem_st = _bot->address_for_index(index + 1);
+ // Calculate rem_end this way because end_index
+ // may be the last valid index in the covered region.
+ HeapWord* rem_end = _bot->address_for_index(end_index) + BOTConstants::N_words;
+ set_remainder_to_point_to_start(rem_st, rem_end);
+ }
+
+ index = end_index + 1;
+ // Calculate threshold_ this way because end_index
+ // may be the last valid index in the covered region.
+ threshold = _bot->address_for_index(end_index) + BOTConstants::N_words;
+ assert(threshold >= blk_end, "Incorrect offset threshold");
+
+ // index_ and threshold_ updated here.
+ *threshold_ = threshold;
+ *index_ = index;
+
+#ifdef ASSERT
+ // The offset can be 0 if the block starts on a boundary. That
+ // is checked by an assertion above.
+ size_t start_index = _bot->index_for(blk_start);
+ HeapWord* boundary = _bot->address_for_index(start_index);
+ assert((_bot->offset_array(orig_index) == 0 && blk_start == boundary) ||
+ (_bot->offset_array(orig_index) > 0 && _bot->offset_array(orig_index) <= BOTConstants::N_words),
+ "offset array should have been set - "
+ "orig_index offset: %u, "
+ "blk_start: " PTR_FORMAT ", "
+ "boundary: " PTR_FORMAT,
+ (uint)_bot->offset_array(orig_index),
+ p2i(blk_start), p2i(boundary));
+ for (size_t j = orig_index + 1; j <= end_index; j++) {
+ assert(_bot->offset_array(j) > 0 &&
+ _bot->offset_array(j) <=
+ (u_char) (BOTConstants::N_words+BOTConstants::N_powers-1),
+ "offset array should have been set - "
+ "%u not > 0 OR %u not <= %u",
+ (uint) _bot->offset_array(j),
+ (uint) _bot->offset_array(j),
+ (uint) (BOTConstants::N_words+BOTConstants::N_powers-1));
+ }
+#endif
+}
+
+void G1BlockOffsetTablePart::verify() const {
+ assert(_space->bottom() < _space->top(), "Only non-empty regions should be verified.");
+ size_t start_card = _bot->index_for(_space->bottom());
+ size_t end_card = _bot->index_for(_space->top() - 1);
+
+ for (size_t current_card = start_card; current_card < end_card; current_card++) {
+ u_char entry = _bot->offset_array(current_card);
+ if (entry < BOTConstants::N_words) {
+ // The entry should point to an object before the current card. Verify that
+ // it is possible to walk from that object in to the current card by just
+ // iterating over the objects following it.
+ HeapWord* card_address = _bot->address_for_index(current_card);
+ HeapWord* obj_end = card_address - entry;
+ while (obj_end < card_address) {
+ HeapWord* obj = obj_end;
+ size_t obj_size = block_size(obj);
+ obj_end = obj + obj_size;
+ guarantee(obj_end > obj && obj_end <= _space->top(),
+ "Invalid object end. obj: " PTR_FORMAT " obj_size: " SIZE_FORMAT " obj_end: " PTR_FORMAT " top: " PTR_FORMAT,
+ p2i(obj), obj_size, p2i(obj_end), p2i(_space->top()));
+ }
+ } else {
+ // Because we refine the BOT based on which cards are dirty there is not much we can verify here.
+ // We need to make sure that we are going backwards and that we don't pass the start of the
+ // corresponding heap region. But that is about all we can verify.
+ size_t backskip = BOTConstants::entry_to_cards_back(entry);
+ guarantee(backskip >= 1, "Must be going back at least one card.");
+
+ size_t max_backskip = current_card - start_card;
+ guarantee(backskip <= max_backskip,
+ "Going backwards beyond the start_card. start_card: " SIZE_FORMAT " current_card: " SIZE_FORMAT " backskip: " SIZE_FORMAT,
+ start_card, current_card, backskip);
+
+ HeapWord* backskip_address = _bot->address_for_index(current_card - backskip);
+ guarantee(backskip_address >= _space->bottom(),
+ "Going backwards beyond bottom of the region: bottom: " PTR_FORMAT ", backskip_address: " PTR_FORMAT,
+ p2i(_space->bottom()), p2i(backskip_address));
+ }
+ }
+}
+
+#ifdef ASSERT
+void G1BlockOffsetTablePart::set_object_can_span(bool can_span) {
+ _object_can_span = can_span;
+}
+#endif
+
+#ifndef PRODUCT
+void
+G1BlockOffsetTablePart::print_on(outputStream* out) {
+ size_t from_index = _bot->index_for(_space->bottom());
+ size_t to_index = _bot->index_for(_space->end());
+ out->print_cr(">> BOT for area [" PTR_FORMAT "," PTR_FORMAT ") "
+ "cards [" SIZE_FORMAT "," SIZE_FORMAT ")",
+ p2i(_space->bottom()), p2i(_space->end()), from_index, to_index);
+ for (size_t i = from_index; i < to_index; ++i) {
+ out->print_cr(" entry " SIZE_FORMAT_W(8) " | " PTR_FORMAT " : %3u",
+ i, p2i(_bot->address_for_index(i)),
+ (uint) _bot->offset_array(i));
+ }
+ out->print_cr(" next offset threshold: " PTR_FORMAT, p2i(_next_offset_threshold));
+ out->print_cr(" next offset index: " SIZE_FORMAT, _next_offset_index);
+}
+#endif // !PRODUCT
+
+HeapWord* G1BlockOffsetTablePart::initialize_threshold_raw() {
+ assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
+ "just checking");
+ _next_offset_index = _bot->index_for_raw(_space->bottom());
+ _next_offset_index++;
+ _next_offset_threshold =
+ _bot->address_for_index_raw(_next_offset_index);
+ return _next_offset_threshold;
+}
+
+void G1BlockOffsetTablePart::zero_bottom_entry_raw() {
+ assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
+ "just checking");
+ size_t bottom_index = _bot->index_for_raw(_space->bottom());
+ assert(_bot->address_for_index_raw(bottom_index) == _space->bottom(),
+ "Precondition of call");
+ _bot->set_offset_array_raw(bottom_index, 0);
+}
+
+HeapWord* G1BlockOffsetTablePart::initialize_threshold() {
+ assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
+ "just checking");
+ _next_offset_index = _bot->index_for(_space->bottom());
+ _next_offset_index++;
+ _next_offset_threshold =
+ _bot->address_for_index(_next_offset_index);
+ return _next_offset_threshold;
+}
+
+void G1BlockOffsetTablePart::set_for_starts_humongous(HeapWord* obj_top, size_t fill_size) {
+ // The first BOT entry should have offset 0.
+ reset_bot();
+ alloc_block(_space->bottom(), obj_top);
+ if (fill_size > 0) {
+ alloc_block(obj_top, fill_size);
+ }
+}