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/*
* Copyright (c) 2001, 2010, 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_implementation/g1/g1CollectedHeap.inline.hpp"
#include "gc_implementation/g1/heapRegionSeq.hpp"
#include "memory/allocation.hpp"
// 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);
}