--- /dev/null 2014-12-12 17:10:47.511674808 +0100 +++ new/src/share/vm/gc_implementation/g1/g1InCSetState.hpp 2014-12-16 11:06:38.075388567 +0100 @@ -0,0 +1,127 @@ +/* + * Copyright (c) 2014, 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. + * + */ + +#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1INCSETSTATE_HPP +#define SHARE_VM_GC_IMPLEMENTATION_G1_G1INCSETSTATE_HPP + +#include "gc_implementation/g1/g1BiasedArray.hpp" +#include "memory/allocation.hpp" + +// Per-region state during garbage collection. +struct InCSetState { + private: + // We use different types to represent the state value. Particularly SPARC puts + // values in structs from "left to right", i.e. MSB to LSB. This results in many + // unnecessary shift operations when loading and storing values of this type. + // This degrades performance significantly (>10%) on that platform. + // Other tested ABIs do not seem to have this problem, and actually tend to + // favor smaller types, so we use the smallest usable type there. + SPARC_ONLY(typedef intptr_t in_cset_state_t;) + NOT_SPARC(typedef int8_t in_cset_state_t;) + + in_cset_state_t _value; + public: + enum { + // Selection of the values were driven to micro-optimize the encoding and + // frequency of the checks. + // The most common check is whether the region is in the collection set or not. + // This encoding allows us to use an != 0 check which in some architectures + // (x86*) can be encoded slightly more efficently than a normal comparison + // against zero. + // The same situation occurs when checking whether the region is humongous + // or not, which is encoded by values < 0. + // The other values are simply encoded in increasing generation order, which + // makes getting the next generation fast by a simple increment. + Humongous = -1, // The region is humongous - note that actually any value < 0 would be possible here. + NotInCSet = 0, // The region is not in the collection set. + Young = 1, // The region is in the collection set and a young region. + Old = 2, // The region is in the collection set and an old region. + Num + }; + + InCSetState() { _value = NotInCSet; } + InCSetState(in_cset_state_t value) { _value = value; } + + in_cset_state_t value() const { return _value; } + + void set_old() { _value = Old; } + + bool is_not_in_cset() const { return _value == NotInCSet; } + bool is_in_cset_or_humongous() const { return _value != NotInCSet; } + bool is_in_cset() const { return _value > NotInCSet; } + bool is_humongous() const { return _value < NotInCSet; } + bool is_young() const { return _value == Young; } + bool is_old() const { return _value == Old; } + +#ifdef ASSERT + bool is_default() const { return is_not_in_cset(); } + bool is_valid() const { return (_value >= Humongous) && (_value < Num); } + bool is_valid_gen() const { return (_value >= Young && _value <= Old); } +#endif +}; + +// Instances of this class are used for quick tests on whether a reference points +// into the collection set and into which generation or is a humongous object +// +// Each of the array's elements indicates whether the corresponding region is in +// the collection set and if so in which generation, or a humongous region. +// +// We use this to speed up reference processing during young collection and +// quickly reclaim humongous objects. For the latter, by making a humongous region +// succeed this test, we sort-of add it to the collection set. During the reference +// iteration closures, when we see a humongous region, we then simply mark it as +// referenced, i.e. live. +class G1InCSetStateFastTestBiasedMappedArray : public G1BiasedMappedArray { + protected: + InCSetState default_value() const { return InCSetState::NotInCSet; } + public: + void set_humongous(uintptr_t index) { + assert(get_by_index(index).is_default(), + err_msg("State at index " INTPTR_FORMAT" should be default but is %d", index, get_by_index(index).value())); + set_by_index(index, InCSetState::Humongous); + } + + void clear_humongous(uintptr_t index) { + set_by_index(index, InCSetState::NotInCSet); + } + + void set_in_young(uintptr_t index) { + assert(get_by_index(index).is_default(), + err_msg("State at index " INTPTR_FORMAT" should be default but is %d", index, get_by_index(index).value())); + set_by_index(index, InCSetState::Young); + } + + void set_in_old(uintptr_t index) { + assert(get_by_index(index).is_default(), + err_msg("State at index " INTPTR_FORMAT" should be default but is %d", index, get_by_index(index).value())); + set_by_index(index, InCSetState::Old); + } + + bool is_in_cset_or_humongous(HeapWord* addr) const { return at(addr).is_in_cset_or_humongous(); } + bool is_in_cset(HeapWord* addr) const { return at(addr).is_in_cset(); } + InCSetState at(HeapWord* addr) const { return get_by_address(addr); } + void clear() { G1BiasedMappedArray::clear(); } +}; + +#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1INCSETSTATE_HPP