--- /dev/null 2017-03-07 11:44:12.271151064 +0100 +++ new/src/share/vm/gc/parallel/psCardTable.cpp 2017-04-25 16:46:20.119171531 +0200 @@ -0,0 +1,676 @@ +/* + * Copyright (c) 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/parallel/gcTaskManager.hpp" +#include "gc/parallel/objectStartArray.inline.hpp" +#include "gc/parallel/parallelScavengeHeap.hpp" +#include "gc/parallel/psCardTable.hpp" +#include "gc/parallel/psPromotionManager.inline.hpp" +#include "gc/parallel/psScavenge.hpp" +#include "gc/parallel/psTasks.hpp" +#include "gc/parallel/psYoungGen.hpp" +#include "oops/oop.inline.hpp" +#include "runtime/prefetch.inline.hpp" + +// Checks an individual oop for missing precise marks. Mark +// may be either dirty or newgen. +class CheckForUnmarkedOops : public OopClosure { + private: + PSYoungGen* _young_gen; + PSCardTable* _card_table; + HeapWord* _unmarked_addr; + + protected: + template void do_oop_work(T* p) { + oop obj = oopDesc::load_decode_heap_oop(p); + if (_young_gen->is_in_reserved(obj) && + !_card_table->addr_is_marked_imprecise(p)) { + // Don't overwrite the first missing card mark + if (_unmarked_addr == NULL) { + _unmarked_addr = (HeapWord*)p; + } + } + } + + public: + CheckForUnmarkedOops(PSYoungGen* young_gen, PSCardTable* card_table) : + _young_gen(young_gen), _card_table(card_table), _unmarked_addr(NULL) { } + + virtual void do_oop(oop* p) { CheckForUnmarkedOops::do_oop_work(p); } + virtual void do_oop(narrowOop* p) { CheckForUnmarkedOops::do_oop_work(p); } + + bool has_unmarked_oop() { + return _unmarked_addr != NULL; + } +}; + +// Checks all objects for the existence of some type of mark, +// precise or imprecise, dirty or newgen. +class CheckForUnmarkedObjects : public ObjectClosure { + private: + PSYoungGen* _young_gen; + PSCardTable* _card_table; + + public: + CheckForUnmarkedObjects() { + ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); + _young_gen = heap->young_gen(); + _card_table = heap->card_table(); + } + + // Card marks are not precise. The current system can leave us with + // a mismatch of precise marks and beginning of object marks. This means + // we test for missing precise marks first. If any are found, we don't + // fail unless the object head is also unmarked. + virtual void do_object(oop obj) { + CheckForUnmarkedOops object_check(_young_gen, _card_table); + obj->oop_iterate_no_header(&object_check); + if (object_check.has_unmarked_oop()) { + guarantee(_card_table->addr_is_marked_imprecise(obj), "Found unmarked young_gen object"); + } + } +}; + +// Checks for precise marking of oops as newgen. +class CheckForPreciseMarks : public OopClosure { + private: + PSYoungGen* _young_gen; + PSCardTable* _card_table; + + protected: + template void do_oop_work(T* p) { + oop obj = oopDesc::load_decode_heap_oop_not_null(p); + if (_young_gen->is_in_reserved(obj)) { + assert(_card_table->addr_is_marked_precise(p), "Found unmarked precise oop"); + _card_table->set_card_newgen(p); + } + } + + public: + CheckForPreciseMarks(PSYoungGen* young_gen, PSCardTable* card_table) : + _young_gen(young_gen), _card_table(card_table) { } + + virtual void do_oop(oop* p) { CheckForPreciseMarks::do_oop_work(p); } + virtual void do_oop(narrowOop* p) { CheckForPreciseMarks::do_oop_work(p); } +}; + +// We get passed the space_top value to prevent us from traversing into +// the old_gen promotion labs, which cannot be safely parsed. + +// Do not call this method if the space is empty. +// It is a waste to start tasks and get here only to +// do no work. If this method needs to be called +// when the space is empty, fix the calculation of +// end_card to allow sp_top == sp->bottom(). + +void PSCardTable::scavenge_contents_parallel(ObjectStartArray* start_array, + MutableSpace* sp, + HeapWord* space_top, + PSPromotionManager* pm, + uint stripe_number, + uint stripe_total) { + int ssize = 128; // Naked constant! Work unit = 64k. + int dirty_card_count = 0; + + // It is a waste to get here if empty. + assert(sp->bottom() < sp->top(), "Should not be called if empty"); + oop* sp_top = (oop*)space_top; + jbyte* start_card = byte_for(sp->bottom()); + jbyte* end_card = byte_for(sp_top - 1) + 1; + oop* last_scanned = NULL; // Prevent scanning objects more than once + // The width of the stripe ssize*stripe_total must be + // consistent with the number of stripes so that the complete slice + // is covered. + size_t slice_width = ssize * stripe_total; + for (jbyte* slice = start_card; slice < end_card; slice += slice_width) { + jbyte* worker_start_card = slice + stripe_number * ssize; + if (worker_start_card >= end_card) + return; // We're done. + + jbyte* worker_end_card = worker_start_card + ssize; + if (worker_end_card > end_card) + worker_end_card = end_card; + + // We do not want to scan objects more than once. In order to accomplish + // this, we assert that any object with an object head inside our 'slice' + // belongs to us. We may need to extend the range of scanned cards if the + // last object continues into the next 'slice'. + // + // Note! ending cards are exclusive! + HeapWord* slice_start = addr_for(worker_start_card); + HeapWord* slice_end = MIN2((HeapWord*) sp_top, addr_for(worker_end_card)); + +#ifdef ASSERT + if (GCWorkerDelayMillis > 0) { + // Delay 1 worker so that it proceeds after all the work + // has been completed. + if (stripe_number < 2) { + os::sleep(Thread::current(), GCWorkerDelayMillis, false); + } + } +#endif + + // If there are not objects starting within the chunk, skip it. + if (!start_array->object_starts_in_range(slice_start, slice_end)) { + continue; + } + // Update our beginning addr + HeapWord* first_object = start_array->object_start(slice_start); + debug_only(oop* first_object_within_slice = (oop*) first_object;) + if (first_object < slice_start) { + last_scanned = (oop*)(first_object + oop(first_object)->size()); + debug_only(first_object_within_slice = last_scanned;) + worker_start_card = byte_for(last_scanned); + } + + // Update the ending addr + if (slice_end < (HeapWord*)sp_top) { + // The subtraction is important! An object may start precisely at slice_end. + HeapWord* last_object = start_array->object_start(slice_end - 1); + slice_end = last_object + oop(last_object)->size(); + // worker_end_card is exclusive, so bump it one past the end of last_object's + // covered span. + worker_end_card = byte_for(slice_end) + 1; + + if (worker_end_card > end_card) + worker_end_card = end_card; + } + + assert(slice_end <= (HeapWord*)sp_top, "Last object in slice crosses space boundary"); + assert(is_valid_card_address(worker_start_card), "Invalid worker start card"); + assert(is_valid_card_address(worker_end_card), "Invalid worker end card"); + // Note that worker_start_card >= worker_end_card is legal, and happens when + // an object spans an entire slice. + assert(worker_start_card <= end_card, "worker start card beyond end card"); + assert(worker_end_card <= end_card, "worker end card beyond end card"); + + jbyte* current_card = worker_start_card; + while (current_card < worker_end_card) { + // Find an unclean card. + while (current_card < worker_end_card && card_is_clean(*current_card)) { + current_card++; + } + jbyte* first_unclean_card = current_card; + + // Find the end of a run of contiguous unclean cards + while (current_card < worker_end_card && !card_is_clean(*current_card)) { + while (current_card < worker_end_card && !card_is_clean(*current_card)) { + current_card++; + } + + if (current_card < worker_end_card) { + // Some objects may be large enough to span several cards. If such + // an object has more than one dirty card, separated by a clean card, + // we will attempt to scan it twice. The test against "last_scanned" + // prevents the redundant object scan, but it does not prevent newly + // marked cards from being cleaned. + HeapWord* last_object_in_dirty_region = start_array->object_start(addr_for(current_card)-1); + size_t size_of_last_object = oop(last_object_in_dirty_region)->size(); + HeapWord* end_of_last_object = last_object_in_dirty_region + size_of_last_object; + jbyte* ending_card_of_last_object = byte_for(end_of_last_object); + assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card"); + if (ending_card_of_last_object > current_card) { + // This means the object spans the next complete card. + // We need to bump the current_card to ending_card_of_last_object + current_card = ending_card_of_last_object; + } + } + } + jbyte* following_clean_card = current_card; + + if (first_unclean_card < worker_end_card) { + oop* p = (oop*) start_array->object_start(addr_for(first_unclean_card)); + assert((HeapWord*)p <= addr_for(first_unclean_card), "checking"); + // "p" should always be >= "last_scanned" because newly GC dirtied + // cards are no longer scanned again (see comment at end + // of loop on the increment of "current_card"). Test that + // hypothesis before removing this code. + // If this code is removed, deal with the first time through + // the loop when the last_scanned is the object starting in + // the previous slice. + assert((p >= last_scanned) || + (last_scanned == first_object_within_slice), + "Should no longer be possible"); + if (p < last_scanned) { + // Avoid scanning more than once; this can happen because + // newgen cards set by GC may a different set than the + // originally dirty set + p = last_scanned; + } + oop* to = (oop*)addr_for(following_clean_card); + + // Test slice_end first! + if ((HeapWord*)to > slice_end) { + to = (oop*)slice_end; + } else if (to > sp_top) { + to = sp_top; + } + + // we know which cards to scan, now clear them + if (first_unclean_card <= worker_start_card+1) + first_unclean_card = worker_start_card+1; + if (following_clean_card >= worker_end_card-1) + following_clean_card = worker_end_card-1; + + while (first_unclean_card < following_clean_card) { + *first_unclean_card++ = clean_card; + } + + const int interval = PrefetchScanIntervalInBytes; + // scan all objects in the range + if (interval != 0) { + while (p < to) { + Prefetch::write(p, interval); + oop m = oop(p); + assert(m->is_oop_or_null(), "Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m)); + pm->push_contents(m); + p += m->size(); + } + pm->drain_stacks_cond_depth(); + } else { + while (p < to) { + oop m = oop(p); + assert(m->is_oop_or_null(), "Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m)); + pm->push_contents(m); + p += m->size(); + } + pm->drain_stacks_cond_depth(); + } + last_scanned = p; + } + // "current_card" is still the "following_clean_card" or + // the current_card is >= the worker_end_card so the + // loop will not execute again. + assert((current_card == following_clean_card) || + (current_card >= worker_end_card), + "current_card should only be incremented if it still equals " + "following_clean_card"); + // Increment current_card so that it is not processed again. + // It may now be dirty because a old-to-young pointer was + // found on it an updated. If it is now dirty, it cannot be + // be safely cleaned in the next iteration. + current_card++; + } + } +} + +// This should be called before a scavenge. +void PSCardTable::verify_all_young_refs_imprecise() { + CheckForUnmarkedObjects check; + + ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); + PSOldGen* old_gen = heap->old_gen(); + + old_gen->object_iterate(&check); +} + +// This should be called immediately after a scavenge, before mutators resume. +void PSCardTable::verify_all_young_refs_precise() { + ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); + PSOldGen* old_gen = heap->old_gen(); + + CheckForPreciseMarks check( + heap->young_gen(), + heap->card_table()); + + old_gen->oop_iterate_no_header(&check); + + verify_all_young_refs_precise_helper(old_gen->object_space()->used_region()); +} + +void PSCardTable::verify_all_young_refs_precise_helper(MemRegion mr) { + PSCardTable* ct = ParallelScavengeHeap::heap()->card_table(); + jbyte* bot = ct->byte_for(mr.start()); + jbyte* top = ct->byte_for(mr.end()); + while(bot <= top) { + assert(*bot == clean_card || *bot == verify_card, "Found unwanted or unknown card mark"); + if (*bot == verify_card) + *bot = youngergen_card; + bot++; + } +} + +bool PSCardTable::addr_is_marked_imprecise(void *addr) { + jbyte* p = byte_for(addr); + jbyte val = *p; + + if (card_is_dirty(val)) + return true; + + if (card_is_newgen(val)) + return true; + + if (card_is_clean(val)) + return false; + + assert(false, "Found unhandled card mark type"); + + return false; +} + +// Also includes verify_card +bool PSCardTable::addr_is_marked_precise(void *addr) { + jbyte* p = byte_for(addr); + jbyte val = *p; + + if (card_is_newgen(val)) + return true; + + if (card_is_verify(val)) + return true; + + if (card_is_clean(val)) + return false; + + if (card_is_dirty(val)) + return false; + + assert(false, "Found unhandled card mark type"); + + return false; +} + +// Assumes that only the base or the end changes. This allows indentification +// of the region that is being resized. The +// CardTableModRefBS::resize_covered_region() is used for the normal case +// where the covered regions are growing or shrinking at the high end. +// The method resize_covered_region_by_end() is analogous to +// CardTableModRefBS::resize_covered_region() but +// for regions that grow or shrink at the low end. +void PSCardTable::resize_covered_region(MemRegion new_region) { + for (int i = 0; i < _cur_covered_regions; i++) { + if (_covered[i].start() == new_region.start()) { + // Found a covered region with the same start as the + // new region. The region is growing or shrinking + // from the start of the region. + resize_covered_region_by_start(new_region); + return; + } + if (_covered[i].start() > new_region.start()) { + break; + } + } + + int changed_region = -1; + for (int j = 0; j < _cur_covered_regions; j++) { + if (_covered[j].end() == new_region.end()) { + changed_region = j; + // This is a case where the covered region is growing or shrinking + // at the start of the region. + assert(changed_region != -1, "Don't expect to add a covered region"); + assert(_covered[changed_region].byte_size() != new_region.byte_size(), + "The sizes should be different here"); + resize_covered_region_by_end(changed_region, new_region); + return; + } + } + // This should only be a new covered region (where no existing + // covered region matches at the start or the end). + assert(_cur_covered_regions < _max_covered_regions, + "An existing region should have been found"); + resize_covered_region_by_start(new_region); +} + +void PSCardTable::resize_covered_region_by_start(MemRegion new_region) { + CardTable::resize_covered_region(new_region); + debug_only(verify_guard();) +} + +void PSCardTable::resize_covered_region_by_end(int changed_region, + MemRegion new_region) { + assert(SafepointSynchronize::is_at_safepoint(), + "Only expect an expansion at the low end at a GC"); + debug_only(verify_guard();) +#ifdef ASSERT + for (int k = 0; k < _cur_covered_regions; k++) { + if (_covered[k].end() == new_region.end()) { + assert(changed_region == k, "Changed region is incorrect"); + break; + } + } +#endif + + // Commit new or uncommit old pages, if necessary. + if (resize_commit_uncommit(changed_region, new_region)) { + // Set the new start of the committed region + resize_update_committed_table(changed_region, new_region); + } + + // Update card table entries + resize_update_card_table_entries(changed_region, new_region); + + // Update the covered region + resize_update_covered_table(changed_region, new_region); + + int ind = changed_region; + log_trace(gc, barrier)("CardTableModRefBS::resize_covered_region: "); + log_trace(gc, barrier)(" _covered[%d].start(): " INTPTR_FORMAT " _covered[%d].last(): " INTPTR_FORMAT, + ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last())); + log_trace(gc, barrier)(" _committed[%d].start(): " INTPTR_FORMAT " _committed[%d].last(): " INTPTR_FORMAT, + ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last())); + log_trace(gc, barrier)(" byte_for(start): " INTPTR_FORMAT " byte_for(last): " INTPTR_FORMAT, + p2i(byte_for(_covered[ind].start())), p2i(byte_for(_covered[ind].last()))); + log_trace(gc, barrier)(" addr_for(start): " INTPTR_FORMAT " addr_for(last): " INTPTR_FORMAT, + p2i(addr_for((jbyte*) _committed[ind].start())), p2i(addr_for((jbyte*) _committed[ind].last()))); + + debug_only(verify_guard();) +} + +bool PSCardTable::resize_commit_uncommit(int changed_region, + MemRegion new_region) { + bool result = false; + // Commit new or uncommit old pages, if necessary. + MemRegion cur_committed = _committed[changed_region]; + assert(_covered[changed_region].end() == new_region.end(), + "The ends of the regions are expected to match"); + // Extend the start of this _committed region to + // to cover the start of any previous _committed region. + // This forms overlapping regions, but never interior regions. + HeapWord* min_prev_start = lowest_prev_committed_start(changed_region); + if (min_prev_start < cur_committed.start()) { + // Only really need to set start of "cur_committed" to + // the new start (min_prev_start) but assertion checking code + // below use cur_committed.end() so make it correct. + MemRegion new_committed = + MemRegion(min_prev_start, cur_committed.end()); + cur_committed = new_committed; + } +#ifdef ASSERT + ParallelScavengeHeap* heap = ParallelScavengeHeap::heap(); + assert(cur_committed.start() == + (HeapWord*) align_size_up((uintptr_t) cur_committed.start(), + os::vm_page_size()), + "Starts should have proper alignment"); +#endif + + jbyte* new_start = byte_for(new_region.start()); + // Round down because this is for the start address + HeapWord* new_start_aligned = + (HeapWord*)align_size_down((uintptr_t)new_start, os::vm_page_size()); + // The guard page is always committed and should not be committed over. + // This method is used in cases where the generation is growing toward + // lower addresses but the guard region is still at the end of the + // card table. That still makes sense when looking for writes + // off the end of the card table. + if (new_start_aligned < cur_committed.start()) { + // Expand the committed region + // + // Case A + // |+ guard +| + // |+ cur committed +++++++++| + // |+ new committed +++++++++++++++++| + // + // Case B + // |+ guard +| + // |+ cur committed +| + // |+ new committed +++++++| + // + // These are not expected because the calculation of the + // cur committed region and the new committed region + // share the same end for the covered region. + // Case C + // |+ guard +| + // |+ cur committed +| + // |+ new committed +++++++++++++++++| + // Case D + // |+ guard +| + // |+ cur committed +++++++++++| + // |+ new committed +++++++| + + HeapWord* new_end_for_commit = + MIN2(cur_committed.end(), _guard_region.start()); + if(new_start_aligned < new_end_for_commit) { + MemRegion new_committed = + MemRegion(new_start_aligned, new_end_for_commit); + os::commit_memory_or_exit((char*)new_committed.start(), + new_committed.byte_size(), !ExecMem, + "card table expansion"); + } + result = true; + } else if (new_start_aligned > cur_committed.start()) { + // Shrink the committed region +#if 0 // uncommitting space is currently unsafe because of the interactions + // of growing and shrinking regions. One region A can uncommit space + // that it owns but which is being used by another region B (maybe). + // Region B has not committed the space because it was already + // committed by region A. + MemRegion uncommit_region = committed_unique_to_self(changed_region, + MemRegion(cur_committed.start(), new_start_aligned)); + if (!uncommit_region.is_empty()) { + if (!os::uncommit_memory((char*)uncommit_region.start(), + uncommit_region.byte_size())) { + // If the uncommit fails, ignore it. Let the + // committed table resizing go even though the committed + // table will over state the committed space. + } + } +#else + assert(!result, "Should be false with current workaround"); +#endif + } + assert(_committed[changed_region].end() == cur_committed.end(), + "end should not change"); + return result; +} + +void PSCardTable::resize_update_committed_table(int changed_region, + MemRegion new_region) { + + jbyte* new_start = byte_for(new_region.start()); + // Set the new start of the committed region + HeapWord* new_start_aligned = + (HeapWord*)align_size_down((uintptr_t)new_start, + os::vm_page_size()); + MemRegion new_committed = MemRegion(new_start_aligned, + _committed[changed_region].end()); + _committed[changed_region] = new_committed; + _committed[changed_region].set_start(new_start_aligned); +} + +void PSCardTable::resize_update_card_table_entries(int changed_region, + MemRegion new_region) { + debug_only(verify_guard();) + MemRegion original_covered = _covered[changed_region]; + // Initialize the card entries. Only consider the + // region covered by the card table (_whole_heap) + jbyte* entry; + if (new_region.start() < _whole_heap.start()) { + entry = byte_for(_whole_heap.start()); + } else { + entry = byte_for(new_region.start()); + } + jbyte* end = byte_for(original_covered.start()); + // If _whole_heap starts at the original covered regions start, + // this loop will not execute. + while (entry < end) { *entry++ = clean_card; } +} + +void PSCardTable::resize_update_covered_table(int changed_region, + MemRegion new_region) { + // Update the covered region + _covered[changed_region].set_start(new_region.start()); + _covered[changed_region].set_word_size(new_region.word_size()); + + // reorder regions. There should only be at most 1 out + // of order. + for (int i = _cur_covered_regions-1 ; i > 0; i--) { + if (_covered[i].start() < _covered[i-1].start()) { + MemRegion covered_mr = _covered[i-1]; + _covered[i-1] = _covered[i]; + _covered[i] = covered_mr; + MemRegion committed_mr = _committed[i-1]; + _committed[i-1] = _committed[i]; + _committed[i] = committed_mr; + break; + } + } +#ifdef ASSERT + for (int m = 0; m < _cur_covered_regions-1; m++) { + assert(_covered[m].start() <= _covered[m+1].start(), + "Covered regions out of order"); + assert(_committed[m].start() <= _committed[m+1].start(), + "Committed regions out of order"); + } +#endif +} + +// Returns the start of any committed region that is lower than +// the target committed region (index ind) and that intersects the +// target region. If none, return start of target region. +// +// ------------- +// | | +// ------------- +// ------------ +// | target | +// ------------ +// ------------- +// | | +// ------------- +// ^ returns this +// +// ------------- +// | | +// ------------- +// ------------ +// | target | +// ------------ +// ------------- +// | | +// ------------- +// ^ returns this + +HeapWord* PSCardTable::lowest_prev_committed_start(int ind) const { + assert(_cur_covered_regions >= 0, "Expecting at least on region"); + HeapWord* min_start = _committed[ind].start(); + for (int j = 0; j < ind; j++) { + HeapWord* this_start = _committed[j].start(); + if ((this_start < min_start) && + !(_committed[j].intersection(_committed[ind])).is_empty()) { + min_start = this_start; + } + } + return min_start; +}