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/*
* Copyright (c) 2001, 2012, 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/collectionSetChooser.hpp"
#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
#include "gc_implementation/g1/g1CollectorPolicy.hpp"
#include "gc_implementation/g1/g1ErgoVerbose.hpp"
#include "memory/space.inline.hpp"
// Even though we don't use the GC efficiency in our heuristics as
// much as we used to, we still order according to GC efficiency. This
// will cause regions with a lot of live objects and large RSets to
// end up at the end of the array. Given that we might skip collecting
// the last few old regions, if after a few mixed GCs the remaining
// have reclaimable bytes under a certain threshold, the hope is that
// the ones we'll skip are ones with both large RSets and a lot of
// live objects, not the ones with just a lot of live objects if we
// ordered according to the amount of reclaimable bytes per region.
static int order_regions(HeapRegion* hr1, HeapRegion* hr2) {
if (hr1 == NULL) {
if (hr2 == NULL) {
return 0;
} else {
return 1;
}
} else if (hr2 == NULL) {
return -1;
}
double gc_eff1 = hr1->gc_efficiency();
double gc_eff2 = hr2->gc_efficiency();
if (gc_eff1 > gc_eff2) {
return -1;
} if (gc_eff1 < gc_eff2) {
return 1;
} else {
return 0;
}
}
static int order_regions(HeapRegion** hr1p, HeapRegion** hr2p) {
return order_regions(*hr1p, *hr2p);
}
CollectionSetChooser::CollectionSetChooser() :
// 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),
100), true /* C_Heap */),
_curr_index(0), _length(0), _first_par_unreserved_idx(0),
_region_live_threshold_bytes(0), _remaining_reclaimable_bytes(0) {
_region_live_threshold_bytes =
HeapRegion::GrainBytes * (size_t) G1MixedGCLiveThresholdPercent / 100;
}
#ifndef PRODUCT
void CollectionSetChooser::verify() {
guarantee(_length <= regions_length(),
err_msg("_length: %u regions length: %u", _length, regions_length()));
guarantee(_curr_index <= _length,
err_msg("_curr_index: %u _length: %u", _curr_index, _length));
uint index = 0;
size_t sum_of_reclaimable_bytes = 0;
while (index < _curr_index) {
guarantee(regions_at(index) == NULL,
"all entries before _curr_index should be NULL");
index += 1;
}
HeapRegion *prev = NULL;
while (index < _length) {
HeapRegion *curr = regions_at(index++);
guarantee(curr != NULL, "Regions in _regions array cannot be NULL");
guarantee(!curr->is_young(), "should not be young!");
guarantee(!curr->isHumongous(), "should not be humongous!");
if (prev != NULL) {
guarantee(order_regions(prev, curr) != 1,
err_msg("GC eff prev: %1.4f GC eff curr: %1.4f",
prev->gc_efficiency(), curr->gc_efficiency()));
}
sum_of_reclaimable_bytes += curr->reclaimable_bytes();
prev = curr;
}
guarantee(sum_of_reclaimable_bytes == _remaining_reclaimable_bytes,
err_msg("reclaimable bytes inconsistent, "
"remaining: "SIZE_FORMAT" sum: "SIZE_FORMAT,
_remaining_reclaimable_bytes, sum_of_reclaimable_bytes));
}
#endif // !PRODUCT
void CollectionSetChooser::sort_regions() {
// First trim any unused portion of the top in the parallel case.
if (_first_par_unreserved_idx > 0) {
assert(_first_par_unreserved_idx <= regions_length(),
"Or we didn't reserved enough length");
regions_trunc_to(_first_par_unreserved_idx);
}
_regions.sort(order_regions);
assert(_length <= regions_length(), "Requirement");
#ifdef ASSERT
for (uint i = 0; i < _length; i++) {
assert(regions_at(i) != NULL, "Should be true by sorting!");
}
#endif // ASSERT
if (G1PrintRegionLivenessInfo) {
G1PrintRegionLivenessInfoClosure cl(gclog_or_tty, "Post-Sorting");
for (uint i = 0; i < _length; ++i) {
HeapRegion* r = regions_at(i);
cl.doHeapRegion(r);
}
}
verify();
}
void CollectionSetChooser::add_region(HeapRegion* hr) {
assert(!hr->isHumongous(),
"Humongous regions shouldn't be added to the collection set");
assert(!hr->is_young(), "should not be young!");
_regions.append(hr);
_length++;
_remaining_reclaimable_bytes += hr->reclaimable_bytes();
hr->calc_gc_efficiency();
}
void CollectionSetChooser::prepare_for_par_region_addition(uint n_regions,
uint chunk_size) {
_first_par_unreserved_idx = 0;
uint n_threads = (uint) ParallelGCThreads;
if (UseDynamicNumberOfGCThreads) {
assert(G1CollectedHeap::heap()->workers()->active_workers() > 0,
"Should have been set earlier");
// This is defensive code. As the assertion above says, the number
// of active threads should be > 0, but in case there is some path
// or some improperly initialized variable with leads to no
// active threads, protect against that in a product build.
n_threads = MAX2(G1CollectedHeap::heap()->workers()->active_workers(),
1U);
}
uint max_waste = n_threads * chunk_size;
// it should be aligned with respect to chunk_size
uint aligned_n_regions = (n_regions + chunk_size - 1) / chunk_size * chunk_size;
assert(aligned_n_regions % chunk_size == 0, "should be aligned");
regions_at_put_grow(aligned_n_regions + max_waste - 1, NULL);
}
uint CollectionSetChooser::claim_array_chunk(uint chunk_size) {
uint res = (uint) Atomic::add((jint) chunk_size,
(volatile jint*) &_first_par_unreserved_idx);
assert(regions_length() > res + chunk_size - 1,
"Should already have been expanded");
return res - chunk_size;
}
void CollectionSetChooser::set_region(uint index, HeapRegion* hr) {
assert(regions_at(index) == NULL, "precondition");
assert(!hr->is_young(), "should not be young!");
regions_at_put(index, hr);
hr->calc_gc_efficiency();
}
void CollectionSetChooser::update_totals(uint region_num,
size_t reclaimable_bytes) {
// Only take the lock if we actually need to update the totals.
if (region_num > 0) {
assert(reclaimable_bytes > 0, "invariant");
// We could have just used atomics instead of taking the
// lock. However, we currently don't have an atomic add for size_t.
MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
_length += region_num;
_remaining_reclaimable_bytes += reclaimable_bytes;
} else {
assert(reclaimable_bytes == 0, "invariant");
}
}
void CollectionSetChooser::clear() {
_regions.clear();
_curr_index = 0;
_length = 0;
_remaining_reclaimable_bytes = 0;
};
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