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/*
Copyright (C) 2005 Apple Inc. All rights reserved.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This library 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public License
along with this library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.
*/
#include "third_party/blink/renderer/platform/wtf/hash_table.h"
#if DUMP_HASHTABLE_STATS || DUMP_HASHTABLE_STATS_PER_TABLE
#include <iomanip>
#include "base/synchronization/lock.h"
namespace WTF {
static base::Lock& HashTableStatsLock() {
DEFINE_THREAD_SAFE_STATIC_LOCAL(base::Lock, lock, ());
return lock;
}
HashTableStats& HashTableStats::instance() {
DEFINE_THREAD_SAFE_STATIC_LOCAL(HashTableStats, stats, ());
return stats;
}
void HashTableStats::copy(const HashTableStats* other) {
numAccesses = other->numAccesses.load(std::memory_order_relaxed);
numRehashes = other->numRehashes.load(std::memory_order_relaxed);
numRemoves = other->numRemoves.load(std::memory_order_relaxed);
numReinserts = other->numReinserts.load(std::memory_order_relaxed);
maxCollisions = other->maxCollisions;
numCollisions = other->numCollisions;
memcpy(collisionGraph.data(), other->collisionGraph.data(),
sizeof(collisionGraph));
}
void HashTableStats::recordCollisionAtCount(int count) {
// The global hash table singleton needs to be atomically updated.
if (this == &instance()) {
base::AutoLock locker(HashTableStatsLock());
RecordCollisionAtCountWithoutLock(count);
} else {
RecordCollisionAtCountWithoutLock(count);
}
}
void HashTableStats::RecordCollisionAtCountWithoutLock(int count) {
if (count > maxCollisions)
maxCollisions = count;
numCollisions++;
collisionGraph[count]++;
}
void HashTableStats::DumpStats() {
// Lock the global hash table singleton while dumping.
if (this == &instance()) {
base::AutoLock locker(HashTableStatsLock());
DumpStatsWithoutLock();
} else {
DumpStatsWithoutLock();
}
}
void HashTableStats::DumpStatsWithoutLock() {
std::stringstream collision_str;
collision_str << std::fixed << std::setprecision(2);
for (int i = 1; i <= maxCollisions; i++) {
collision_str << " " << collisionGraph[i] << " lookups with exactly "
<< i << " collisions ("
<< (100.0 * (collisionGraph[i] - collisionGraph[i + 1]) /
numAccesses)
<< "% , " << (100.0 * collisionGraph[i] / numAccesses)
<< "% with this many or more)\n";
}
DLOG(INFO) << std::fixed << std::setprecision(2)
<< "WTF::HashTable statistics:\n"
<< " " << numAccesses << " accesses\n"
<< " " << numCollisions << " total collisions, average "
<< (1.0 * (numAccesses + numCollisions) / numAccesses)
<< " probes per access\n"
<< " longest collision chain: " << maxCollisions << "\n"
<< collision_str.str() << " " << numRehashes << " rehashes\n"
<< " " << numReinserts << " reinserts";
}
} // namespace WTF
#endif
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