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 /*

  * Copyright (c) 2001, 2009, 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

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 #include "incls/_precompiled.incl"

 #include "incls/_heapRegionSeq.cpp.incl"

 // Local to this file.

 static int orderRegions(HeapRegion** hr1p, HeapRegion** hr2p) {

   if ((*hr1p)->end() <= (*hr2p)->bottom()) return -1;

   else if ((*hr2p)->end() <= (*hr1p)->bottom()) return 1;

   else if (*hr1p == *hr2p) return 0;

   else {

     assert(false, "We should never compare distinct overlapping regions.");

   }

   return 0;

 }

 HeapRegionSeq::HeapRegionSeq(const size_t max_size) :

   _alloc_search_start(0),

   // The line below is the worst bit of C++ hackery I've ever written

   // (Detlefs, 11/23).  You should think of it as equivalent to

   // "_regions(100, true)": initialize the growable array and inform it

   // that it should allocate its elem array(s) on the C heap.

   //

   // The first argument, however, is actually a comma expression

   // (set_allocation_type(this, C_HEAP), 100). The purpose of the

   // set_allocation_type() call is to replace the default allocation

   // type for embedded objects STACK_OR_EMBEDDED with C_HEAP. It will

   // allow to pass the assert in GenericGrowableArray() which checks

   // that a growable array object must be on C heap if elements are.

   //

   // Note: containing object is allocated on C heap since it is CHeapObj.

   //

   _regions((ResourceObj::set_allocation_type((address)&_regions,

                                              ResourceObj::C_HEAP),

             (int)max_size),

            true),

   _next_rr_candidate(0),

   _seq_bottom(NULL)

 {}

 // Private methods.

 HeapWord*

 HeapRegionSeq::alloc_obj_from_region_index(int ind, size_t word_size) {

   assert(G1CollectedHeap::isHumongous(word_size),

          "Allocation size should be humongous");

   int cur = ind;

   int first = cur;

   size_t sumSizes = 0;

   while (cur < _regions.length() && sumSizes < word_size) {

     // Loop invariant:

     //  For all i in [first, cur):

     //       _regions.at(i)->is_empty()

     //    && _regions.at(i) is contiguous with its predecessor, if any

     //  && sumSizes is the sum of the sizes of the regions in the interval

     //       [first, cur)

     HeapRegion* curhr = _regions.at(cur);

     if (curhr->is_empty()

         && (first == cur

             || (_regions.at(cur-1)->end() ==

                 curhr->bottom()))) {

       sumSizes += curhr->capacity() / HeapWordSize;

     } else {

       first = cur + 1;

       sumSizes = 0;

     }

     cur++;

   }

   if (sumSizes >= word_size) {

     _alloc_search_start = cur;

     // We need to initialize the region(s) we just discovered. This is

     // a bit tricky given that it can happen concurrently with

     // refinement threads refining cards on these regions and

     // potentially wanting to refine the BOT as they are scanning

     // those cards (this can happen shortly after a cleanup; see CR

     // 6991377). So we have to set up the region(s) carefully and in

     // a specific order.

     // Currently, allocs_are_zero_filled() returns false. The zero

     // filling infrastructure will be going away soon (see CR 6977804).

     // So no need to do anything else here.

     bool zf = G1CollectedHeap::heap()->allocs_are_zero_filled();

     assert(!zf, "not supported");

     // This will be the "starts humongous" region.

     HeapRegion* first_hr = _regions.at(first);

     {

       MutexLockerEx x(ZF_mon, Mutex::_no_safepoint_check_flag);

       first_hr->set_zero_fill_allocated();

     }

     // The header of the new object will be placed at the bottom of

     // the first region.

     HeapWord* new_obj = first_hr->bottom();

     // This will be the new end of the first region in the series that

     // should also match the end of the last region in the seriers.

     // (Note: sumSizes = "region size" x "number of regions we found").

     HeapWord* new_end = new_obj + sumSizes;

     // This will be the new top of the first region that will reflect

     // this allocation.

     HeapWord* new_top = new_obj + word_size;

     // First, we need to zero the header of the space that we will be

     // allocating. When we update top further down, some refinement

     // threads might try to scan the region. By zeroing the header we

     // ensure that any thread that will try to scan the region will

     // come across the zero klass word and bail out.

     //

     // NOTE: It would not have been correct to have used

     // CollectedHeap::fill_with_object() and make the space look like

     // an int array. The thread that is doing the allocation will

     // later update the object header to a potentially different array

     // type and, for a very short period of time, the klass and length

     // fields will be inconsistent. This could cause a refinement

     // thread to calculate the object size incorrectly.

     Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);

     // We will set up the first region as "starts humongous". This

     // will also update the BOT covering all the regions to reflect

     // that there is a single object that starts at the bottom of the

     // first region.

     first_hr->set_startsHumongous(new_end);

     // Then, if there are any, we will set up the "continues

     // humongous" regions.

     HeapRegion* hr = NULL;

     for (int i = first + 1; i < cur; ++i) {

       hr = _regions.at(i);

       {

         MutexLockerEx x(ZF_mon, Mutex::_no_safepoint_check_flag);

         hr->set_zero_fill_allocated();

       }

       hr->set_continuesHumongous(first_hr);

     }

     // If we have "continues humongous" regions (hr != NULL), then the

     // end of the last one should match new_end.

     assert(hr == NULL || hr->end() == new_end, "sanity");

     // Up to this point no concurrent thread would have been able to

     // do any scanning on any region in this series. All the top

     // fields still point to bottom, so the intersection between

     // [bottom,top] and [card_start,card_end] will be empty. Before we

     // update the top fields, we'll do a storestore to make sure that

     // no thread sees the update to top before the zeroing of the

     // object header and the BOT initialization.

     OrderAccess::storestore();

     // Now that the BOT and the object header have been initialized,

     // we can update top of the "starts humongous" region.

     assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),

            "new_top should be in this region");

     first_hr->set_top(new_top);

     // Now, we will update the top fields of the "continues humongous"

     // regions. The reason we need to do this is that, otherwise,

     // these regions would look empty and this will confuse parts of

     // G1. For example, the code that looks for a consecutive number

     // of empty regions will consider them empty and try to

     // re-allocate them. We can extend is_empty() to also include

     // !continuesHumongous(), but it is easier to just update the top

     // fields here.

     hr = NULL;

     for (int i = first + 1; i < cur; ++i) {

       hr = _regions.at(i);

       if ((i + 1) == cur) {

         // last continues humongous region

         assert(hr->bottom() < new_top && new_top <= hr->end(),

                "new_top should fall on this region");

         hr->set_top(new_top);

       } else {

         // not last one

         assert(new_top > hr->end(), "new_top should be above this region");

         hr->set_top(hr->end());

       }

     }

     // If we have continues humongous regions (hr != NULL), then the

     // end of the last one should match new_end and its top should

     // match new_top.

     assert(hr == NULL ||

            (hr->end() == new_end && hr->top() == new_top), "sanity");

     return new_obj;

   } else {

     // If we started from the beginning, we want to know why we can't alloc.

     return NULL;

   }

 }

 void HeapRegionSeq::print_empty_runs() {

   int empty_run = 0;

   int n_empty = 0;

   int empty_run_start;

   for (int i = 0; i < _regions.length(); i++) {

     HeapRegion* r = _regions.at(i);

     if (r->continuesHumongous()) continue;

     if (r->is_empty()) {

       assert(!r->isHumongous(), "H regions should not be empty.");

       if (empty_run == 0) empty_run_start = i;

       empty_run++;

       n_empty++;

     } else {

       if (empty_run > 0) {

         gclog_or_tty->print("  %d:%d", empty_run_start, empty_run);

         empty_run = 0;

       }

     }

   }

   if (empty_run > 0) {

     gclog_or_tty->print(" %d:%d", empty_run_start, empty_run);

   }

   gclog_or_tty->print_cr(" [tot = %d]", n_empty);

 }

 int HeapRegionSeq::find(HeapRegion* hr) {

   // FIXME: optimized for adjacent regions of fixed size.

   int ind = hr->hrs_index();

   if (ind != -1) {

     assert(_regions.at(ind) == hr, "Mismatch");

   }

   return ind;

 }

 // Public methods.

 void HeapRegionSeq::insert(HeapRegion* hr) {

   assert(!_regions.is_full(), "Too many elements in HeapRegionSeq");

   if (_regions.length() == 0

       || _regions.top()->end() <= hr->bottom()) {

     hr->set_hrs_index(_regions.length());

     _regions.append(hr);

   } else {

     _regions.append(hr);

     _regions.sort(orderRegions);

     for (int i = 0; i < _regions.length(); i++) {

       _regions.at(i)->set_hrs_index(i);

     }

   }

   char* bot = (char*)_regions.at(0)->bottom();

   if (_seq_bottom == NULL || bot < _seq_bottom) _seq_bottom = bot;

 }

 size_t HeapRegionSeq::length() {

   return _regions.length();

 }

 size_t HeapRegionSeq::free_suffix() {

   size_t res = 0;

   int first = _regions.length() - 1;

   int cur = first;

   while (cur >= 0 &&

          (_regions.at(cur)->is_empty()

           && (first == cur

               || (_regions.at(cur+1)->bottom() ==

                   _regions.at(cur)->end())))) {

       res++;

       cur--;

   }

   return res;

 }

 HeapWord* HeapRegionSeq::obj_allocate(size_t word_size) {

   int cur = _alloc_search_start;

   // Make sure "cur" is a valid index.

   assert(cur >= 0, "Invariant.");

   HeapWord* res = alloc_obj_from_region_index(cur, word_size);

   if (res == NULL)

     res = alloc_obj_from_region_index(0, word_size);

   return res;

 }

 void HeapRegionSeq::iterate(HeapRegionClosure* blk) {

   iterate_from((HeapRegion*)NULL, blk);

 }

 // The first argument r is the heap region at which iteration begins.

 // This operation runs fastest when r is NULL, or the heap region for

 // which a HeapRegionClosure most recently returned true, or the

 // heap region immediately to its right in the sequence.  In all

 // other cases a linear search is required to find the index of r.

 void HeapRegionSeq::iterate_from(HeapRegion* r, HeapRegionClosure* blk) {

   // :::: FIXME ::::

   // Static cache value is bad, especially when we start doing parallel

   // remembered set update. For now just don't cache anything (the

   // code in the def'd out blocks).

 #if 0

   static int cached_j = 0;

 #endif

   int len = _regions.length();

   int j = 0;

   // Find the index of r.

   if (r != NULL) {

 #if 0

     assert(cached_j >= 0, "Invariant.");

     if ((cached_j < len) && (r == _regions.at(cached_j))) {

       j = cached_j;

     } else if ((cached_j + 1 < len) && (r == _regions.at(cached_j + 1))) {

       j = cached_j + 1;

     } else {

       j = find(r);

 #endif

       if (j < 0) {

         j = 0;

       }

 #if 0

     }

 #endif

   }

   int i;

   for (i = j; i < len; i += 1) {

     int res = blk->doHeapRegion(_regions.at(i));

     if (res) {

 #if 0

       cached_j = i;

 #endif

       blk->incomplete();

       return;

     }

   }

   for (i = 0; i < j; i += 1) {

     int res = blk->doHeapRegion(_regions.at(i));

     if (res) {

 #if 0

       cached_j = i;

 #endif

       blk->incomplete();

       return;

     }

   }

 }

 void HeapRegionSeq::iterate_from(int idx, HeapRegionClosure* blk) {

   int len = _regions.length();

   int i;

   for (i = idx; i < len; i++) {

     if (blk->doHeapRegion(_regions.at(i))) {

       blk->incomplete();

       return;

     }

   }

   for (i = 0; i < idx; i++) {

     if (blk->doHeapRegion(_regions.at(i))) {

       blk->incomplete();

       return;

     }

   }

 }

 MemRegion HeapRegionSeq::shrink_by(size_t shrink_bytes,

                                    size_t& num_regions_deleted) {

   assert(shrink_bytes % os::vm_page_size() == 0, "unaligned");

   assert(shrink_bytes % HeapRegion::GrainBytes == 0, "unaligned");

   if (_regions.length() == 0) {

     num_regions_deleted = 0;

     return MemRegion();

   }

   int j = _regions.length() - 1;

   HeapWord* end = _regions.at(j)->end();

   HeapWord* last_start = end;

   while (j >= 0 && shrink_bytes > 0) {

     HeapRegion* cur = _regions.at(j);

     // We have to leave humongous regions where they are,

     // and work around them.

     if (cur->isHumongous()) {

       return MemRegion(last_start, end);

     }

     assert(cur == _regions.top(), "Should be top");

     if (!cur->is_empty()) break;

     cur->reset_zero_fill();

     shrink_bytes -= cur->capacity();

     num_regions_deleted++;

     _regions.pop();

     last_start = cur->bottom();

     // We need to delete these somehow, but can't currently do so here: if

     // we do, the ZF thread may still access the deleted region.  We'll

     // leave this here as a reminder that we have to do something about

     // this.

     // delete cur;

     j--;

   }

   return MemRegion(last_start, end);

 }

 class PrintHeapRegionClosure : public  HeapRegionClosure {

 public:

   bool doHeapRegion(HeapRegion* r) {

     gclog_or_tty->print(PTR_FORMAT ":", r);

     r->print();

     return false;

   }

 };

 void HeapRegionSeq::print() {

   PrintHeapRegionClosure cl;

   iterate(&cl);

 }