111 lines
3.4 KiB
C++
111 lines
3.4 KiB
C++
/*
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* HighContentionAllocator.actor.cpp
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*
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* This source file is part of the FoundationDB open source project
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*
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* Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "HighContentionAllocator.h"
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namespace FDB {
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ACTOR Future<Standalone<StringRef>> _allocate(Reference<Transaction> tr, Subspace counters, Subspace recent) {
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state int64_t start = 0;
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state int64_t window = 0;
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loop {
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FDBStandalone<RangeResultRef> range = wait(tr->getRange(counters.range(), 1, true, true));
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if (range.size() > 0) {
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start = counters.unpack(range[0].key).getInt(0);
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}
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state bool windowAdvanced = false;
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loop {
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// if thread safety is needed, this should be locked {
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if (windowAdvanced) {
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tr->clear(KeyRangeRef(counters.key(), counters.get(start).key()));
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tr->setOption(FDBTransactionOption::FDB_TR_OPTION_NEXT_WRITE_NO_WRITE_CONFLICT_RANGE);
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tr->clear(KeyRangeRef(recent.key(), recent.get(start).key()));
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}
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int64_t inc = 1;
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tr->atomicOp(counters.get(start).key(), StringRef((uint8_t*)&inc, 8), FDB_MUTATION_TYPE_ADD);
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Future<Optional<FDBStandalone<ValueRef>>> countFuture = tr->get(counters.get(start).key(), true);
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// }
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Optional<FDBStandalone<ValueRef>> countValue = wait(countFuture);
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int64_t count = 0;
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if (countValue.present()) {
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if (countValue.get().size() != 8) {
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throw invalid_directory_layer_metadata();
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}
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count = *(int64_t*)countValue.get().begin();
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}
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window = HighContentionAllocator::windowSize(start);
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if (count * 2 < window) {
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break;
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}
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start += window;
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windowAdvanced = true;
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}
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loop {
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state int64_t candidate = deterministicRandom()->randomInt(start, start + window);
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// if thread safety is needed, this should be locked {
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state Future<FDBStandalone<RangeResultRef>> latestCounter = tr->getRange(counters.range(), 1, true, true);
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state Future<Optional<FDBStandalone<ValueRef>>> candidateValue = tr->get(recent.get(candidate).key());
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tr->setOption(FDBTransactionOption::FDB_TR_OPTION_NEXT_WRITE_NO_WRITE_CONFLICT_RANGE);
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tr->set(recent.get(candidate).key(), ValueRef());
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// }
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wait(success(latestCounter) && success(candidateValue));
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int64_t currentWindowStart = 0;
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if (latestCounter.get().size() > 0) {
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currentWindowStart = counters.unpack(latestCounter.get()[0].key).getInt(0);
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}
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if (currentWindowStart > start) {
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break;
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}
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if (!candidateValue.get().present()) {
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tr->addWriteConflictKey(recent.get(candidate).key());
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return Tuple().append(candidate).pack();
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}
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}
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}
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}
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Future<Standalone<StringRef>> HighContentionAllocator::allocate(Reference<Transaction> const& tr) const {
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return _allocate(tr, counters, recent);
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}
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int64_t HighContentionAllocator::windowSize(int64_t start) {
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if (start < 255) {
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return 64;
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}
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if (start < 65535) {
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return 1024;
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}
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return 8192;
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}
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} // namespace FDB
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