jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/parNew/parCardTableModRefBS.cpp@2e6857353b2c (annotated)

src/share/vm/gc_implementation/parNew/parCardTableModRefBS.cpp@2e6857353b2c (annotated)

src/share/vm/gc_implementation/parNew/parCardTableModRefBS.cpp

Thu, 04 Oct 2012 10:04:13 -0700

author: johnc
date: Thu, 04 Oct 2012 10:04:13 -0700
changeset 4130: 2e6857353b2c
parent 3900: d2a62e0f25eb
child 4153: b9a9ed0f8eeb
permissions: -rw-r--r--

8000311: G1: ParallelGCThreads==0 broken
Summary: Divide by zero error, if ParallelGCThreads is 0, when adjusting the PLAB size.
Reviewed-by: jmasa, jcoomes

 /*
  * Copyright (c) 2007, 2011, 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 "memory/allocation.inline.hpp"
 #include "memory/cardTableModRefBS.hpp"
 #include "memory/cardTableRS.hpp"
 #include "memory/sharedHeap.hpp"
 #include "memory/space.inline.hpp"
 #include "memory/universe.hpp"
 #include "oops/oop.inline.hpp"
 #include "runtime/java.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "runtime/virtualspace.hpp"
 #include "runtime/vmThread.hpp"
 void CardTableModRefBS::non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,
                                                              OopsInGenClosure* cl,
                                                              CardTableRS* ct,
                                                              int n_threads) {
   assert(n_threads > 0, "Error: expected n_threads > 0");
   assert((n_threads == 1 && ParallelGCThreads == 0) ||
          n_threads <= (int)ParallelGCThreads,
          "# worker threads != # requested!");
   assert(!Thread::current()->is_VM_thread() || (n_threads == 1), "There is only 1 VM thread");
   assert(UseDynamicNumberOfGCThreads ||
          !FLAG_IS_DEFAULT(ParallelGCThreads) ||
          n_threads == (int)ParallelGCThreads,
          "# worker threads != # requested!");
   // Make sure the LNC array is valid for the space.
   jbyte**   lowest_non_clean;
   uintptr_t lowest_non_clean_base_chunk_index;
   size_t    lowest_non_clean_chunk_size;
   get_LNC_array_for_space(sp, lowest_non_clean,
                           lowest_non_clean_base_chunk_index,
                           lowest_non_clean_chunk_size);
   uint n_strides = n_threads * ParGCStridesPerThread;
   SequentialSubTasksDone* pst = sp->par_seq_tasks();
   // Sets the condition for completion of the subtask (how many threads
   // need to finish in order to be done).
   pst->set_n_threads(n_threads);
   pst->set_n_tasks(n_strides);
   uint stride = 0;
   while (!pst->is_task_claimed(/* reference */ stride)) {
     process_stride(sp, mr, stride, n_strides, cl, ct,
                    lowest_non_clean,
                    lowest_non_clean_base_chunk_index,
                    lowest_non_clean_chunk_size);
   }
   if (pst->all_tasks_completed()) {
     // Clear lowest_non_clean array for next time.
     intptr_t first_chunk_index = addr_to_chunk_index(mr.start());
     uintptr_t last_chunk_index  = addr_to_chunk_index(mr.last());
     for (uintptr_t ch = first_chunk_index; ch <= last_chunk_index; ch++) {
       intptr_t ind = ch - lowest_non_clean_base_chunk_index;
       assert(0 <= ind && ind < (intptr_t)lowest_non_clean_chunk_size,
              "Bounds error");
       lowest_non_clean[ind] = NULL;
     }
   }
 }
 void
 CardTableModRefBS::
 process_stride(Space* sp,
                MemRegion used,
                jint stride, int n_strides,
                OopsInGenClosure* cl,
                CardTableRS* ct,
                jbyte** lowest_non_clean,
                uintptr_t lowest_non_clean_base_chunk_index,
                size_t    lowest_non_clean_chunk_size) {
   // We go from higher to lower addresses here; it wouldn't help that much
   // because of the strided parallelism pattern used here.
   // Find the first card address of the first chunk in the stride that is
   // at least "bottom" of the used region.
   jbyte*    start_card  = byte_for(used.start());
   jbyte*    end_card    = byte_after(used.last());
   uintptr_t start_chunk = addr_to_chunk_index(used.start());
   uintptr_t start_chunk_stride_num = start_chunk % n_strides;
   jbyte* chunk_card_start;
   if ((uintptr_t)stride >= start_chunk_stride_num) {
     chunk_card_start = (jbyte*)(start_card +
                                 (stride - start_chunk_stride_num) *
                                 ParGCCardsPerStrideChunk);
   } else {
     // Go ahead to the next chunk group boundary, then to the requested stride.
     chunk_card_start = (jbyte*)(start_card +
                                 (n_strides - start_chunk_stride_num + stride) *
                                 ParGCCardsPerStrideChunk);
   }
   while (chunk_card_start < end_card) {
     // Even though we go from lower to higher addresses below, the
     // strided parallelism can interleave the actual processing of the
     // dirty pages in various ways. For a specific chunk within this
     // stride, we take care to avoid double scanning or missing a card
     // by suitably initializing the "min_done" field in process_chunk_boundaries()
     // below, together with the dirty region extension accomplished in
     // DirtyCardToOopClosure::do_MemRegion().
     jbyte*    chunk_card_end = chunk_card_start + ParGCCardsPerStrideChunk;
     // Invariant: chunk_mr should be fully contained within the "used" region.
     MemRegion chunk_mr       = MemRegion(addr_for(chunk_card_start),
                                          chunk_card_end >= end_card ?
                                            used.end() : addr_for(chunk_card_end));
     assert(chunk_mr.word_size() > 0, "[chunk_card_start > used_end)");
     assert(used.contains(chunk_mr), "chunk_mr should be subset of used");
     DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, precision(),
                                                      cl->gen_boundary());
     ClearNoncleanCardWrapper clear_cl(dcto_cl, ct);
     // Process the chunk.
     process_chunk_boundaries(sp,
                              dcto_cl,
                              chunk_mr,
                              used,
                              lowest_non_clean,
                              lowest_non_clean_base_chunk_index,
                              lowest_non_clean_chunk_size);
     // We want the LNC array updates above in process_chunk_boundaries
     // to be visible before any of the card table value changes as a
     // result of the dirty card iteration below.
     OrderAccess::storestore();
     // We do not call the non_clean_card_iterate_serial() version because
     // we want to clear the cards: clear_cl here does the work of finding
     // contiguous dirty ranges of cards to process and clear.
     clear_cl.do_MemRegion(chunk_mr);
     // Find the next chunk of the stride.
     chunk_card_start += ParGCCardsPerStrideChunk * n_strides;
   }
 }
 // If you want a talkative process_chunk_boundaries,
 // then #define NOISY(x) x
 #ifdef NOISY
 #error "Encountered a global preprocessor flag, NOISY, which might clash with local definition to follow"
 #else
 #define NOISY(x)
 #endif
 void
 CardTableModRefBS::
 process_chunk_boundaries(Space* sp,
                          DirtyCardToOopClosure* dcto_cl,
                          MemRegion chunk_mr,
                          MemRegion used,
                          jbyte** lowest_non_clean,
                          uintptr_t lowest_non_clean_base_chunk_index,
                          size_t    lowest_non_clean_chunk_size)
 {
   // We must worry about non-array objects that cross chunk boundaries,
   // because such objects are both precisely and imprecisely marked:
   // .. if the head of such an object is dirty, the entire object
   //    needs to be scanned, under the interpretation that this
   //    was an imprecise mark
   // .. if the head of such an object is not dirty, we can assume
   //    precise marking and it's efficient to scan just the dirty
   //    cards.
   // In either case, each scanned reference must be scanned precisely
   // once so as to avoid cloning of a young referent. For efficiency,
   // our closures depend on this property and do not protect against
   // double scans.
   uintptr_t cur_chunk_index = addr_to_chunk_index(chunk_mr.start());
   cur_chunk_index           = cur_chunk_index - lowest_non_clean_base_chunk_index;
   NOISY(tty->print_cr("===========================================================================");)
   NOISY(tty->print_cr(" process_chunk_boundary: Called with [" PTR_FORMAT "," PTR_FORMAT ")",
                       chunk_mr.start(), chunk_mr.end());)
   // First, set "our" lowest_non_clean entry, which would be
   // used by the thread scanning an adjoining left chunk with
   // a non-array object straddling the mutual boundary.
   // Find the object that spans our boundary, if one exists.
   // first_block is the block possibly straddling our left boundary.
   HeapWord* first_block = sp->block_start(chunk_mr.start());
   assert((chunk_mr.start() != used.start()) || (first_block == chunk_mr.start()),
          "First chunk should always have a co-initial block");
   // Does the block straddle the chunk's left boundary, and is it
   // a non-array object?
   if (first_block < chunk_mr.start()        // first block straddles left bdry
       && sp->block_is_obj(first_block)      // first block is an object
       && !(oop(first_block)->is_objArray()  // first block is not an array (arrays are precisely dirtied)
            || oop(first_block)->is_typeArray())) {
     // Find our least non-clean card, so that a left neighbour
     // does not scan an object straddling the mutual boundary
     // too far to the right, and attempt to scan a portion of
     // that object twice.
     jbyte* first_dirty_card = NULL;
     jbyte* last_card_of_first_obj =
         byte_for(first_block + sp->block_size(first_block) - 1);
     jbyte* first_card_of_cur_chunk = byte_for(chunk_mr.start());
     jbyte* last_card_of_cur_chunk = byte_for(chunk_mr.last());
     jbyte* last_card_to_check =
       (jbyte*) MIN2((intptr_t) last_card_of_cur_chunk,
                     (intptr_t) last_card_of_first_obj);
     // Note that this does not need to go beyond our last card
     // if our first object completely straddles this chunk.
     for (jbyte* cur = first_card_of_cur_chunk;
          cur <= last_card_to_check; cur++) {
       jbyte val = *cur;
       if (card_will_be_scanned(val)) {
         first_dirty_card = cur; break;
       } else {
         assert(!card_may_have_been_dirty(val), "Error");
       }
     }
     if (first_dirty_card != NULL) {
       NOISY(tty->print_cr(" LNC: Found a dirty card at " PTR_FORMAT " in current chunk",
                     first_dirty_card);)
       assert(0 <= cur_chunk_index && cur_chunk_index < lowest_non_clean_chunk_size,
              "Bounds error.");
       assert(lowest_non_clean[cur_chunk_index] == NULL,
              "Write exactly once : value should be stable hereafter for this round");
       lowest_non_clean[cur_chunk_index] = first_dirty_card;
     } NOISY(else {
       tty->print_cr(" LNC: Found no dirty card in current chunk; leaving LNC entry NULL");
       // In the future, we could have this thread look for a non-NULL value to copy from its
       // right neighbour (up to the end of the first object).
       if (last_card_of_cur_chunk < last_card_of_first_obj) {
         tty->print_cr(" LNC: BEWARE!!! first obj straddles past right end of chunk:\n"
                       "   might be efficient to get value from right neighbour?");
       }
     })
   } else {
     // In this case we can help our neighbour by just asking them
     // to stop at our first card (even though it may not be dirty).
     NOISY(tty->print_cr(" LNC: first block is not a non-array object; setting LNC to first card of current chunk");)
     assert(lowest_non_clean[cur_chunk_index] == NULL, "Write once : value should be stable hereafter");
     jbyte* first_card_of_cur_chunk = byte_for(chunk_mr.start());
     lowest_non_clean[cur_chunk_index] = first_card_of_cur_chunk;
   }
   NOISY(tty->print_cr(" process_chunk_boundary: lowest_non_clean[" INTPTR_FORMAT "] = " PTR_FORMAT
                 "   which corresponds to the heap address " PTR_FORMAT,
                 cur_chunk_index, lowest_non_clean[cur_chunk_index],
                 (lowest_non_clean[cur_chunk_index] != NULL)
                 ? addr_for(lowest_non_clean[cur_chunk_index])
                 : NULL);)
   NOISY(tty->print_cr("---------------------------------------------------------------------------");)
   // Next, set our own max_to_do, which will strictly/exclusively bound
   // the highest address that we will scan past the right end of our chunk.
   HeapWord* max_to_do = NULL;
   if (chunk_mr.end() < used.end()) {
     // This is not the last chunk in the used region.
     // What is our last block? We check the first block of
     // the next (right) chunk rather than strictly check our last block
     // because it's potentially more efficient to do so.
     HeapWord* const last_block = sp->block_start(chunk_mr.end());
     assert(last_block <= chunk_mr.end(), "In case this property changes.");
     if ((last_block == chunk_mr.end())     // our last block does not straddle boundary
         || !sp->block_is_obj(last_block)   // last_block isn't an object
         || oop(last_block)->is_objArray()  // last_block is an array (precisely marked)
         || oop(last_block)->is_typeArray()) {
       max_to_do = chunk_mr.end();
       NOISY(tty->print_cr(" process_chunk_boundary: Last block on this card is not a non-array object;\n"
                          "   max_to_do left at " PTR_FORMAT, max_to_do);)
     } else {
       assert(last_block < chunk_mr.end(), "Tautology");
       // It is a non-array object that straddles the right boundary of this chunk.
       // last_obj_card is the card corresponding to the start of the last object
       // in the chunk.  Note that the last object may not start in
       // the chunk.
       jbyte* const last_obj_card = byte_for(last_block);
       const jbyte val = *last_obj_card;
       if (!card_will_be_scanned(val)) {
         assert(!card_may_have_been_dirty(val), "Error");
         // The card containing the head is not dirty.  Any marks on
         // subsequent cards still in this chunk must have been made
         // precisely; we can cap processing at the end of our chunk.
         max_to_do = chunk_mr.end();
         NOISY(tty->print_cr(" process_chunk_boundary: Head of last object on this card is not dirty;\n"
                             "   max_to_do left at " PTR_FORMAT,
                             max_to_do);)
       } else {
         // The last object must be considered dirty, and extends onto the
         // following chunk.  Look for a dirty card in that chunk that will
         // bound our processing.
         jbyte* limit_card = NULL;
         const size_t last_block_size = sp->block_size(last_block);
         jbyte* const last_card_of_last_obj =
           byte_for(last_block + last_block_size - 1);
         jbyte* const first_card_of_next_chunk = byte_for(chunk_mr.end());
         // This search potentially goes a long distance looking
         // for the next card that will be scanned, terminating
         // at the end of the last_block, if no earlier dirty card
         // is found.
         assert(byte_for(chunk_mr.end()) - byte_for(chunk_mr.start()) == ParGCCardsPerStrideChunk,
                "last card of next chunk may be wrong");
         for (jbyte* cur = first_card_of_next_chunk;
              cur <= last_card_of_last_obj; cur++) {
           const jbyte val = *cur;
           if (card_will_be_scanned(val)) {
             NOISY(tty->print_cr(" Found a non-clean card " PTR_FORMAT " with value 0x%x",
                                 cur, (int)val);)
             limit_card = cur; break;
           } else {
             assert(!card_may_have_been_dirty(val), "Error: card can't be skipped");
           }
         }
         if (limit_card != NULL) {
           max_to_do = addr_for(limit_card);
           assert(limit_card != NULL && max_to_do != NULL, "Error");
           NOISY(tty->print_cr(" process_chunk_boundary: Found a dirty card at " PTR_FORMAT
                         "   max_to_do set at " PTR_FORMAT " which is before end of last block in chunk: "
                         PTR_FORMAT " + " PTR_FORMAT " = " PTR_FORMAT,
                         limit_card, max_to_do, last_block, last_block_size, (last_block+last_block_size));)
         } else {
           // The following is a pessimistic value, because it's possible
           // that a dirty card on a subsequent chunk has been cleared by
           // the time we get to look at it; we'll correct for that further below,
           // using the LNC array which records the least non-clean card
           // before cards were cleared in a particular chunk.
           limit_card = last_card_of_last_obj;
           max_to_do = last_block + last_block_size;
           assert(limit_card != NULL && max_to_do != NULL, "Error");
           NOISY(tty->print_cr(" process_chunk_boundary: Found no dirty card before end of last block in chunk\n"
                               "   Setting limit_card to " PTR_FORMAT
                               " and max_to_do " PTR_FORMAT " + " PTR_FORMAT " = " PTR_FORMAT,
                               limit_card, last_block, last_block_size, max_to_do);)
         }
         assert(0 < cur_chunk_index+1 && cur_chunk_index+1 < lowest_non_clean_chunk_size,
                "Bounds error.");
         // It is possible that a dirty card for the last object may have been
         // cleared before we had a chance to examine it. In that case, the value
         // will have been logged in the LNC for that chunk.
         // We need to examine as many chunks to the right as this object
         // covers. However, we need to bound this checking to the largest
         // entry in the LNC array: this is because the heap may expand
         // after the LNC array has been created but before we reach this point,
         // and the last block in our chunk may have been expanded to include
         // the expansion delta (and possibly subsequently allocated from, so
         // it wouldn't be sufficient to check whether that last block was
         // or was not an object at this point).
         uintptr_t last_chunk_index_to_check = addr_to_chunk_index(last_block + last_block_size - 1)
                                               - lowest_non_clean_base_chunk_index;
         const uintptr_t last_chunk_index    = addr_to_chunk_index(used.last())
                                               - lowest_non_clean_base_chunk_index;
         if (last_chunk_index_to_check > last_chunk_index) {
           assert(last_block + last_block_size > used.end(),
                  err_msg("Inconsistency detected: last_block [" PTR_FORMAT "," PTR_FORMAT "]"
                          " does not exceed used.end() = " PTR_FORMAT ","
                          " yet last_chunk_index_to_check " INTPTR_FORMAT
                          " exceeds last_chunk_index " INTPTR_FORMAT,
                          last_chunk_index_to_check, last_chunk_index));
           assert(sp->used_region().end() > used.end(),
                  err_msg("Expansion did not happen: "
                          "[" PTR_FORMAT "," PTR_FORMAT ") -> [" PTR_FORMAT "," PTR_FORMAT ")",
                          sp->used_region().start(), sp->used_region().end(), used.start(), used.end()));
           NOISY(tty->print_cr(" process_chunk_boundary: heap expanded; explicitly bounding last_chunk");)
           last_chunk_index_to_check = last_chunk_index;
         }
         for (uintptr_t lnc_index = cur_chunk_index + 1;
              lnc_index <= last_chunk_index_to_check;
              lnc_index++) {
           jbyte* lnc_card = lowest_non_clean[lnc_index];
           if (lnc_card != NULL) {
             // we can stop at the first non-NULL entry we find
             if (lnc_card <= limit_card) {
               NOISY(tty->print_cr(" process_chunk_boundary: LNC card " PTR_FORMAT " is lower than limit_card " PTR_FORMAT,
                                   "   max_to_do will be lowered to " PTR_FORMAT " from " PTR_FORMAT,
                                   lnc_card, limit_card, addr_for(lnc_card), max_to_do);)
               limit_card = lnc_card;
               max_to_do = addr_for(limit_card);
               assert(limit_card != NULL && max_to_do != NULL, "Error");
             }
             // In any case, we break now
             break;
           }  // else continue to look for a non-NULL entry if any
         }
         assert(limit_card != NULL && max_to_do != NULL, "Error");
       }
       assert(max_to_do != NULL, "OOPS 1 !");
     }
     assert(max_to_do != NULL, "OOPS 2!");
   } else {
     max_to_do = used.end();
     NOISY(tty->print_cr(" process_chunk_boundary: Last chunk of this space;\n"
                   "   max_to_do left at " PTR_FORMAT,
                   max_to_do);)
   }
   assert(max_to_do != NULL, "OOPS 3!");
   // Now we can set the closure we're using so it doesn't to beyond
   // max_to_do.
   dcto_cl->set_min_done(max_to_do);
 #ifndef PRODUCT
   dcto_cl->set_last_bottom(max_to_do);
 #endif
   NOISY(tty->print_cr("===========================================================================\n");)
 }
 #undef NOISY
 void
 CardTableModRefBS::
 get_LNC_array_for_space(Space* sp,
                         jbyte**& lowest_non_clean,
                         uintptr_t& lowest_non_clean_base_chunk_index,
                         size_t& lowest_non_clean_chunk_size) {
   int       i        = find_covering_region_containing(sp->bottom());
   MemRegion covered  = _covered[i];
   size_t    n_chunks = chunks_to_cover(covered);
   // Only the first thread to obtain the lock will resize the
   // LNC array for the covered region.  Any later expansion can't affect
   // the used_at_save_marks region.
   // (I observed a bug in which the first thread to execute this would
   // resize, and then it would cause "expand_and_allocate" that would
   // increase the number of chunks in the covered region.  Then a second
   // thread would come and execute this, see that the size didn't match,
   // and free and allocate again.  So the first thread would be using a
   // freed "_lowest_non_clean" array.)
   // Do a dirty read here. If we pass the conditional then take the rare
   // event lock and do the read again in case some other thread had already
   // succeeded and done the resize.
   int cur_collection = Universe::heap()->total_collections();
   if (_last_LNC_resizing_collection[i] != cur_collection) {
     MutexLocker x(ParGCRareEvent_lock);
     if (_last_LNC_resizing_collection[i] != cur_collection) {
       if (_lowest_non_clean[i] == NULL ||
           n_chunks != _lowest_non_clean_chunk_size[i]) {
         // Should we delete the old?
         if (_lowest_non_clean[i] != NULL) {
           assert(n_chunks != _lowest_non_clean_chunk_size[i],
                  "logical consequence");
           FREE_C_HEAP_ARRAY(CardPtr, _lowest_non_clean[i], mtGC);
           _lowest_non_clean[i] = NULL;
         }
         // Now allocate a new one if necessary.
         if (_lowest_non_clean[i] == NULL) {
           _lowest_non_clean[i]                  = NEW_C_HEAP_ARRAY(CardPtr, n_chunks, mtGC);
           _lowest_non_clean_chunk_size[i]       = n_chunks;
           _lowest_non_clean_base_chunk_index[i] = addr_to_chunk_index(covered.start());
           for (int j = 0; j < (int)n_chunks; j++)
             _lowest_non_clean[i][j] = NULL;
         }
       }
       _last_LNC_resizing_collection[i] = cur_collection;
     }
   }
   // In any case, now do the initialization.
   lowest_non_clean                  = _lowest_non_clean[i];
   lowest_non_clean_base_chunk_index = _lowest_non_clean_base_chunk_index[i];
   lowest_non_clean_chunk_size       = _lowest_non_clean_chunk_size[i];
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/parNew/parCardTableModRefBS.cpp@2e6857353b2c (annotated)

src/share/vm/gc_implementation/parNew/parCardTableModRefBS.cpp