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Bugfix for issue 33; reduce lock contention in Get(), parallel benchmarks.

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- Fix for issue 33 (non-null-terminated result from
  leveldb_property_value())

- Support for running multiple instances of a benchmark in parallel.

- Reduce lock contention on Get():
  (1) Do not hold the lock while searching memtables.
  (2) Shard block and table caches 16-ways.

  Benchmark for evaluating this change:
  $ db_bench --benchmarks=fillseq1,readrandom --threads=$n
  (fillseq1 is a small hack to make sure fillseq runs once regardless
  of number of threads specified on the command line).



git-svn-id: https://leveldb.googlecode.com/svn/trunk@49 62dab493-f737-651d-591e-8d6aee1b9529
main
gabor@google.com 14 years ago
parent ab323f7e1e
commit e3584f9c28
7 changed files with 510 additions and 259 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Show Stats Download Patch File Download Diff File
  1. 3
      db/c.cc
  2. 526
      db/db_bench.cc
  3. 34
      db/db_impl.cc
  4. 141
      util/cache.cc
  5. 39
      util/cache_test.cc
  6. 11
      util/histogram.cc
  7. 1
      util/histogram.h

3
db/c.cc
Unescape View File

@ -196,7 +196,8 @@ char* leveldb_property_value(
const char* propname) {
std::string tmp;
if (db->rep->GetProperty(Slice(propname), &tmp)) {
return CopyString(tmp);
// We use strdup() since we expect human readable output.
return strdup(tmp.c_str());
} else {
return NULL;
}

526
db/db_bench.cc
Unescape View File

@ -14,6 +14,7 @@
#include "port/port.h"
#include "util/crc32c.h"
#include "util/histogram.h"
#include "util/mutexlock.h"
#include "util/random.h"
#include "util/testutil.h"
@ -60,6 +61,9 @@ static int FLAGS_num = 1000000;
// Number of read operations to do. If negative, do FLAGS_num reads.
static int FLAGS_reads = -1;
// Number of concurrent threads to run.
static int FLAGS_threads = 1;
// Size of each value
static int FLAGS_value_size = 100;
@ -91,8 +95,9 @@ static const char* FLAGS_db = "/tmp/dbbench";
namespace leveldb {
// Helper for quickly generating random data.
namespace {
// Helper for quickly generating random data.
class RandomGenerator {
private:
std::string data_;
@ -136,6 +141,152 @@ static Slice TrimSpace(Slice s) {
return Slice(s.data() + start, limit - start);
}
static void AppendWithSpace(std::string* str, Slice msg) {
if (msg.empty()) return;
if (!str->empty()) {
str->push_back(' ');
}
str->append(msg.data(), msg.size());
}
class Stats {
private:
double start_;
double finish_;
double seconds_;
int done_;
int next_report_;
int64_t bytes_;
double last_op_finish_;
Histogram hist_;
std::string message_;
public:
Stats() { Start(); }
void Start() {
next_report_ = 100;
last_op_finish_ = start_;
hist_.Clear();
done_ = 0;
bytes_ = 0;
seconds_ = 0;
start_ = Env::Default()->NowMicros();
finish_ = start_;
message_.clear();
}
void Merge(const Stats& other) {
hist_.Merge(other.hist_);
done_ += other.done_;
bytes_ += other.bytes_;
seconds_ += other.seconds_;
if (other.start_ < start_) start_ = other.start_;
if (other.finish_ > finish_) finish_ = other.finish_;
// Just keep the messages from one thread
if (message_.empty()) message_ = other.message_;
}
void Stop() {
finish_ = Env::Default()->NowMicros();
seconds_ = (finish_ - start_) * 1e-6;
}
void AddMessage(Slice msg) {
AppendWithSpace(&message_, msg);
}
void FinishedSingleOp() {
if (FLAGS_histogram) {
double now = Env::Default()->NowMicros();
double micros = now - last_op_finish_;
hist_.Add(micros);
if (micros > 20000) {
fprintf(stderr, "long op: %.1f micros%30s\r", micros, "");
fflush(stderr);
}
last_op_finish_ = now;
}
done_++;
if (done_ >= next_report_) {
if (next_report_ < 1000) next_report_ += 100;
else if (next_report_ < 5000) next_report_ += 500;
else if (next_report_ < 10000) next_report_ += 1000;
else if (next_report_ < 50000) next_report_ += 5000;
else if (next_report_ < 100000) next_report_ += 10000;
else if (next_report_ < 500000) next_report_ += 50000;
else next_report_ += 100000;
fprintf(stderr, "... finished %d ops%30s\r", done_, "");
fflush(stderr);
}
}
void AddBytes(int64_t n) {
bytes_ += n;
}
void Report(const Slice& name) {
// Pretend at least one op was done in case we are running a benchmark
// that does not call FinishedSingleOp().
if (done_ < 1) done_ = 1;
std::string extra;
if (bytes_ > 0) {
// Rate is computed on actual elapsed time, not the sum of per-thread
// elapsed times.
double elapsed = (finish_ - start_) * 1e-6;
char rate[100];
snprintf(rate, sizeof(rate), "%6.1f MB/s",
(bytes_ / 1048576.0) / elapsed);
extra = rate;
}
AppendWithSpace(&extra, message_);
fprintf(stdout, "%-12s : %11.3f micros/op;%s%s\n",
name.ToString().c_str(),
seconds_ * 1e6 / done_,
(extra.empty() ? "" : " "),
extra.c_str());
if (FLAGS_histogram) {
fprintf(stdout, "Microseconds per op:\n%s\n", hist_.ToString().c_str());
}
fflush(stdout);
}
};
// State shared by all concurrent executions of the same benchmark.
struct SharedState {
port::Mutex mu;
port::CondVar cv;
int total;
// Each thread goes through the following states:
// (1) initializing
// (2) waiting for others to be initialized
// (3) running
// (4) done
int num_initialized;
int num_done;
bool start;
SharedState() : cv(&mu) { }
};
// Per-thread state for concurrent executions of the same benchmark.
struct ThreadState {
int tid; // 0..n-1 when running in n threads
Random rand; // Has different seeds for different threads
Stats stats;
ThreadState(int index)
: tid(index),
rand(1000 + index) {
}
};
}
class Benchmark {
@ -143,20 +294,11 @@ class Benchmark {
Cache* cache_;
DB* db_;
int num_;
int value_size_;
int entries_per_batch_;
WriteOptions write_options_;
int reads_;
int heap_counter_;
double start_;
double last_op_finish_;
int64_t bytes_;
std::string message_;
std::string post_message_;
Histogram hist_;
RandomGenerator gen_;
Random rand_;
// State kept for progress messages
int done_;
int next_report_; // When to report next
void PrintHeader() {
const int kKeySize = 16;
@ -232,94 +374,15 @@ class Benchmark {
#endif
}
void Start() {
start_ = Env::Default()->NowMicros() * 1e-6;
bytes_ = 0;
message_.clear();
last_op_finish_ = start_;
hist_.Clear();
done_ = 0;
next_report_ = 100;
}
void FinishedSingleOp() {
if (FLAGS_histogram) {
double now = Env::Default()->NowMicros() * 1e-6;
double micros = (now - last_op_finish_) * 1e6;
hist_.Add(micros);
if (micros > 20000) {
fprintf(stderr, "long op: %.1f micros%30s\r", micros, "");
fflush(stderr);
}
last_op_finish_ = now;
}
done_++;
if (done_ >= next_report_) {
if (next_report_ < 1000) next_report_ += 100;
else if (next_report_ < 5000) next_report_ += 500;
else if (next_report_ < 10000) next_report_ += 1000;
else if (next_report_ < 50000) next_report_ += 5000;
else if (next_report_ < 100000) next_report_ += 10000;
else if (next_report_ < 500000) next_report_ += 50000;
else next_report_ += 100000;
fprintf(stderr, "... finished %d ops%30s\r", done_, "");
fflush(stderr);
}
}
void Stop(const Slice& name) {
double finish = Env::Default()->NowMicros() * 1e-6;
// Pretend at least one op was done in case we are running a benchmark
// that does nto call FinishedSingleOp().
if (done_ < 1) done_ = 1;
if (bytes_ > 0) {
char rate[100];
snprintf(rate, sizeof(rate), "%6.1f MB/s",
(bytes_ / 1048576.0) / (finish - start_));
if (!message_.empty()) {
message_ = std::string(rate) + " " + message_;
} else {
message_ = rate;
}
}
fprintf(stdout, "%-12s : %11.3f micros/op;%s%s\n",
name.ToString().c_str(),
(finish - start_) * 1e6 / done_,
(message_.empty() ? "" : " "),
message_.c_str());
if (FLAGS_histogram) {
fprintf(stdout, "Microseconds per op:\n%s\n", hist_.ToString().c_str());
}
fflush(stdout);
if (!post_message_.empty()) {
fprintf(stdout, "\n%s\n", post_message_.c_str());
post_message_.clear();
}
}
public:
enum Order {
SEQUENTIAL,
RANDOM
};
enum DBState {
FRESH,
EXISTING
};
Benchmark()
: cache_(FLAGS_cache_size >= 0 ? NewLRUCache(FLAGS_cache_size) : NULL),
db_(NULL),
num_(FLAGS_num),
value_size_(FLAGS_value_size),
entries_per_batch_(1),
reads_(FLAGS_reads < 0 ? FLAGS_num : FLAGS_reads),
heap_counter_(0),
bytes_(0),
rand_(301) {
heap_counter_(0) {
std::vector<std::string> files;
Env::Default()->GetChildren(FLAGS_db, &files);
for (int i = 0; i < files.size(); i++) {
@ -353,98 +416,203 @@ class Benchmark {
benchmarks = sep + 1;
}
Start();
// Reset parameters that may be overriddden bwlow
num_ = FLAGS_num;
reads_ = num_;
value_size_ = FLAGS_value_size;
entries_per_batch_ = 1;
write_options_ = WriteOptions();
void (Benchmark::*method)(ThreadState*) = NULL;
bool fresh_db = false;
WriteOptions write_options;
bool known = true;
if (name == Slice("fillseq")) {
Write(write_options, SEQUENTIAL, FRESH, num_, FLAGS_value_size, 1);
fresh_db = true;
method = &Benchmark::WriteSeq;
} else if (name == Slice("fillbatch")) {
Write(write_options, SEQUENTIAL, FRESH, num_, FLAGS_value_size, 1000);
fresh_db = true;
entries_per_batch_ = 1000;
method = &Benchmark::WriteSeq;
} else if (name == Slice("fillrandom")) {
Write(write_options, RANDOM, FRESH, num_, FLAGS_value_size, 1);
fresh_db = true;
method = &Benchmark::WriteRandom;
} else if (name == Slice("overwrite")) {
Write(write_options, RANDOM, EXISTING, num_, FLAGS_value_size, 1);
fresh_db = false;
method = &Benchmark::WriteRandom;
} else if (name == Slice("fillsync")) {
write_options.sync = true;
Write(write_options, RANDOM, FRESH, num_ / 1000, FLAGS_value_size, 1);
fresh_db = true;
num_ /= 1000;
write_options_.sync = true;
method = &Benchmark::WriteRandom;
} else if (name == Slice("fill100K")) {
Write(write_options, RANDOM, FRESH, num_ / 1000, 100 * 1000, 1);
fresh_db = true;
num_ /= 1000;
value_size_ = 100 * 1000;
method = &Benchmark::WriteRandom;
} else if (name == Slice("readseq")) {
ReadSequential();
method = &Benchmark::ReadSequential;
} else if (name == Slice("readreverse")) {
ReadReverse();
method = &Benchmark::ReadReverse;
} else if (name == Slice("readrandom")) {
ReadRandom();
method = &Benchmark::ReadRandom;
} else if (name == Slice("readhot")) {
ReadHot();
method = &Benchmark::ReadHot;
} else if (name == Slice("readrandomsmall")) {
int n = reads_;
reads_ /= 1000;
ReadRandom();
reads_ = n;
method = &Benchmark::ReadRandom;
} else if (name == Slice("compact")) {
Compact();
method = &Benchmark::Compact;
} else if (name == Slice("crc32c")) {
Crc32c(4096, "(4K per op)");
method = &Benchmark::Crc32c;
} else if (name == Slice("acquireload")) {
AcquireLoad();
method = &Benchmark::AcquireLoad;
} else if (name == Slice("snappycomp")) {
SnappyCompress();
method = &Benchmark::SnappyCompress;
} else if (name == Slice("snappyuncomp")) {
SnappyUncompress();
method = &Benchmark::SnappyUncompress;
} else if (name == Slice("heapprofile")) {
HeapProfile();
} else if (name == Slice("stats")) {
PrintStats();
} else {
known = false;
if (name != Slice()) { // No error message for empty name
fprintf(stderr, "unknown benchmark '%s'\n", name.ToString().c_str());
}
}
if (known) {
Stop(name);
if (fresh_db) {
if (FLAGS_use_existing_db) {
fprintf(stdout, "%-12s : skipped (--use_existing_db is true)\n",
name.ToString().c_str());
method = NULL;
} else {
delete db_;
db_ = NULL;
DestroyDB(FLAGS_db, Options());
Open();
}
}
if (method != NULL) {
RunBenchmark(name, method);
}
}
}
private:
void Crc32c(int size, const char* label) {
struct ThreadArg {
Benchmark* bm;
SharedState* shared;
ThreadState* thread;
void (Benchmark::*method)(ThreadState*);
};
static void ThreadBody(void* v) {
ThreadArg* arg = reinterpret_cast<ThreadArg*>(v);
SharedState* shared = arg->shared;
ThreadState* thread = arg->thread;
{
MutexLock l(&shared->mu);
shared->num_initialized++;
if (shared->num_initialized >= shared->total) {
shared->cv.SignalAll();
}
while (!shared->start) {
shared->cv.Wait();
}
}
thread->stats.Start();
(arg->bm->*(arg->method))(thread);
thread->stats.Stop();
{
MutexLock l(&shared->mu);
shared->num_done++;
if (shared->num_done >= shared->total) {
shared->cv.SignalAll();
}
}
}
void RunBenchmark(Slice name, void (Benchmark::*method)(ThreadState*)) {
const int n = FLAGS_threads;
SharedState shared;
shared.total = n;
shared.num_initialized = 0;
shared.num_done = 0;
shared.start = false;
ThreadArg* arg = new ThreadArg[n];
for (int i = 0; i < n; i++) {
arg[i].bm = this;
arg[i].method = method;
arg[i].shared = &shared;
arg[i].thread = new ThreadState(i);
Env::Default()->StartThread(ThreadBody, &arg[i]);
}
shared.mu.Lock();
while (shared.num_initialized < n) {
shared.cv.Wait();
}
shared.start = true;
shared.cv.SignalAll();
while (shared.num_done < n) {
shared.cv.Wait();
}
shared.mu.Unlock();
for (int i = 1; i < n; i++) {
arg[0].thread->stats.Merge(arg[i].thread->stats);
}
arg[0].thread->stats.Report(name);
for (int i = 0; i < n; i++) {
delete arg[i].thread;
}
delete[] arg;
}
void Crc32c(ThreadState* thread) {
// Checksum about 500MB of data total
const int size = 4096;
const char* label = "(4K per op)";
std::string data(size, 'x');
int64_t bytes = 0;
uint32_t crc = 0;
while (bytes < 500 * 1048576) {
crc = crc32c::Value(data.data(), size);
FinishedSingleOp();
thread->stats.FinishedSingleOp();
bytes += size;
}
// Print so result is not dead
fprintf(stderr, "... crc=0x%x\r", static_cast<unsigned int>(crc));
bytes_ = bytes;
message_ = label;
thread->stats.AddBytes(bytes);
thread->stats.AddMessage(label);
}
void AcquireLoad() {
void AcquireLoad(ThreadState* thread) {
int dummy;
port::AtomicPointer ap(&dummy);
int count = 0;
void *ptr = NULL;
message_ = "(each op is 1000 loads)";
thread->stats.AddMessage("(each op is 1000 loads)");
while (count < 100000) {
for (int i = 0; i < 1000; i++) {
ptr = ap.Acquire_Load();
}
count++;
FinishedSingleOp();
thread->stats.FinishedSingleOp();
}
if (ptr == NULL) exit(1); // Disable unused variable warning.
}
void SnappyCompress() {
Slice input = gen_.Generate(Options().block_size);
void SnappyCompress(ThreadState* thread) {
RandomGenerator gen;
Slice input = gen.Generate(Options().block_size);
int64_t bytes = 0;
int64_t produced = 0;
bool ok = true;
@ -453,22 +621,23 @@ class Benchmark {
ok = port::Snappy_Compress(input.data(), input.size(), &compressed);
produced += compressed.size();
bytes += input.size();
FinishedSingleOp();
thread->stats.FinishedSingleOp();
}
if (!ok) {
message_ = "(snappy failure)";
thread->stats.AddMessage("(snappy failure)");
} else {
char buf[100];
snprintf(buf, sizeof(buf), "(output: %.1f%%)",
(produced * 100.0) / bytes);
message_ = buf;
bytes_ = bytes;
thread->stats.AddMessage(buf);
thread->stats.AddBytes(bytes);
}
}
void SnappyUncompress() {
Slice input = gen_.Generate(Options().block_size);
void SnappyUncompress(ThreadState* thread) {
RandomGenerator gen;
Slice input = gen.Generate(Options().block_size);
std::string compressed;
bool ok = port::Snappy_Compress(input.data(), input.size(), &compressed);
int64_t bytes = 0;
@ -477,14 +646,14 @@ class Benchmark {
ok = port::Snappy_Uncompress(compressed.data(), compressed.size(),
uncompressed);
bytes += input.size();
FinishedSingleOp();
thread->stats.FinishedSingleOp();
}
delete[] uncompressed;
if (!ok) {
message_ = "(snappy failure)";
thread->stats.AddMessage("(snappy failure)");
} else {
bytes_ = bytes;
thread->stats.AddBytes(bytes);
}
}
@ -501,95 +670,97 @@ class Benchmark {
}
}
void Write(const WriteOptions& options, Order order, DBState state,
int num_entries, int value_size, int entries_per_batch) {
if (state == FRESH) {
if (FLAGS_use_existing_db) {
message_ = "skipping (--use_existing_db is true)";
return;
void WriteSeq(ThreadState* thread) {
DoWrite(thread, true);
}
delete db_;
db_ = NULL;
DestroyDB(FLAGS_db, Options());
Open();
Start(); // Do not count time taken to destroy/open
void WriteRandom(ThreadState* thread) {
DoWrite(thread, false);
}
if (num_entries != num_) {
void DoWrite(ThreadState* thread, bool seq) {
if (num_ != FLAGS_num) {
char msg[100];
snprintf(msg, sizeof(msg), "(%d ops)", num_entries);
message_ = msg;
snprintf(msg, sizeof(msg), "(%d ops)", num_);
thread->stats.AddMessage(msg);
}
RandomGenerator gen;
WriteBatch batch;
Status s;
std::string val;
for (int i = 0; i < num_entries; i += entries_per_batch) {
int64_t bytes = 0;
for (int i = 0; i < num_; i += entries_per_batch_) {
batch.Clear();
for (int j = 0; j < entries_per_batch; j++) {
const int k = (order == SEQUENTIAL) ? i+j : (rand_.Next() % FLAGS_num);
for (int j = 0; j < entries_per_batch_; j++) {
const int k = seq ? i+j : (thread->rand.Next() % FLAGS_num);
char key[100];
snprintf(key, sizeof(key), "%016d", k);
batch.Put(key, gen_.Generate(value_size));
bytes_ += value_size + strlen(key);
FinishedSingleOp();
batch.Put(key, gen.Generate(value_size_));
bytes += value_size_ + strlen(key);
thread->stats.FinishedSingleOp();
}
s = db_->Write(options, &batch);
s = db_->Write(write_options_, &batch);
if (!s.ok()) {
fprintf(stderr, "put error: %s\n", s.ToString().c_str());
exit(1);
}
}
thread->stats.AddBytes(bytes);
}
void ReadSequential() {
void ReadSequential(ThreadState* thread) {
Iterator* iter = db_->NewIterator(ReadOptions());
int i = 0;
int64_t bytes = 0;
for (iter->SeekToFirst(); i < reads_ && iter->Valid(); iter->Next()) {
bytes_ += iter->key().size() + iter->value().size();
FinishedSingleOp();
bytes += iter->key().size() + iter->value().size();
thread->stats.FinishedSingleOp();
++i;
}
delete iter;
thread->stats.AddBytes(bytes);
}
void ReadReverse() {
void ReadReverse(ThreadState* thread) {
Iterator* iter = db_->NewIterator(ReadOptions());
int i = 0;
int64_t bytes = 0;
for (iter->SeekToLast(); i < reads_ && iter->Valid(); iter->Prev()) {
bytes_ += iter->key().size() + iter->value().size();
FinishedSingleOp();
bytes += iter->key().size() + iter->value().size();
thread->stats.FinishedSingleOp();
++i;
}
delete iter;
thread->stats.AddBytes(bytes);
}
void ReadRandom() {
void ReadRandom(ThreadState* thread) {
ReadOptions options;
std::string value;
for (int i = 0; i < reads_; i++) {
char key[100];
const int k = rand_.Next() % FLAGS_num;
const int k = thread->rand.Next() % FLAGS_num;
snprintf(key, sizeof(key), "%016d", k);
db_->Get(options, key, &value);
FinishedSingleOp();
thread->stats.FinishedSingleOp();
}
}
void ReadHot() {
void ReadHot(ThreadState* thread) {
ReadOptions options;
std::string value;
const int range = (FLAGS_num + 99) / 100;
for (int i = 0; i < reads_; i++) {
char key[100];
const int k = rand_.Next() % range;
const int k = thread->rand.Next() % range;
snprintf(key, sizeof(key), "%016d", k);
db_->Get(options, key, &value);
FinishedSingleOp();
thread->stats.FinishedSingleOp();
}
}
void Compact() {
void Compact(ThreadState* thread) {
DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
dbi->TEST_CompactMemTable();
int max_level_with_files = 1;
@ -609,10 +780,9 @@ class Benchmark {
void PrintStats() {
std::string stats;
if (!db_->GetProperty("leveldb.stats", &stats)) {
message_ = "(failed)";
} else {
post_message_ = stats;
stats = "(failed)";
}
fprintf(stdout, "\n%s\n", stats.c_str());
}
static void WriteToFile(void* arg, const char* buf, int n) {
@ -625,13 +795,13 @@ class Benchmark {
WritableFile* file;
Status s = Env::Default()->NewWritableFile(fname, &file);
if (!s.ok()) {
message_ = s.ToString();
fprintf(stderr, "%s\n", s.ToString().c_str());
return;
}
bool ok = port::GetHeapProfile(WriteToFile, file);
delete file;
if (!ok) {
message_ = "not supported";
fprintf(stderr, "heap profiling not supported\n");
Env::Default()->DeleteFile(fname);
}
}
@ -661,6 +831,8 @@ int main(int argc, char** argv) {
FLAGS_num = n;
} else if (sscanf(argv[i], "--reads=%d%c", &n, &junk) == 1) {
FLAGS_reads = n;
} else if (sscanf(argv[i], "--threads=%d%c", &n, &junk) == 1) {
FLAGS_threads = n;
} else if (sscanf(argv[i], "--value_size=%d%c", &n, &junk) == 1) {
FLAGS_value_size = n;
} else if (sscanf(argv[i], "--write_buffer_size=%d%c", &n, &junk) == 1) {

34
db/db_impl.cc
Unescape View File

@ -989,27 +989,37 @@ Status DBImpl::Get(const ReadOptions& options,
snapshot = versions_->LastSequence();
}
// First look in the memtable, then in the immutable memtable (if any).
LookupKey lkey(key, snapshot);
if (mem_->Get(lkey, value, &s)) {
return s;
}
if (imm_ != NULL && imm_->Get(lkey, value, &s)) {
return s;
}
// Not in memtable(s); try live files in level order
MemTable* mem = mem_;
MemTable* imm = imm_;
Version* current = versions_->current();
mem->Ref();
if (imm != NULL) imm->Ref();
current->Ref();
bool have_stat_update = false;
Version::GetStats stats;
{ // Unlock while reading from files
// Unlock while reading from files and memtables
{
mutex_.Unlock();
// First look in the memtable, then in the immutable memtable (if any).
LookupKey lkey(key, snapshot);
if (mem_->Get(lkey, value, &s)) {
// Done
} else if (imm_ != NULL && imm_->Get(lkey, value, &s)) {
// Done
} else {
s = current->Get(options, lkey, value, &stats);
have_stat_update = true;
}
mutex_.Lock();
}
if (current->UpdateStats(stats)) {
if (have_stat_update && current->UpdateStats(stats)) {
MaybeScheduleCompaction();
}
mem->Unref();
if (imm != NULL) imm->Unref();
current->Unref();
return s;
}

141
util/cache.cc
Unescape View File

@ -30,7 +30,8 @@ struct LRUHandle {
LRUHandle* prev;
size_t charge; // TODO(opt): Only allow uint32_t?
size_t key_length;
size_t refs; // TODO(opt): Pack with "key_length"?
uint32_t refs;
uint32_t hash; // Hash of key(); used for fast sharding and comparisons
char key_data[1]; // Beginning of key
Slice key() const {
@ -54,12 +55,12 @@ class HandleTable {
HandleTable() : length_(0), elems_(0), list_(NULL) { Resize(); }
~HandleTable() { delete[] list_; }
LRUHandle* Lookup(LRUHandle* h) {
return *FindPointer(h);
LRUHandle* Lookup(const Slice& key, uint32_t hash) {
return *FindPointer(key, hash);
}
LRUHandle* Insert(LRUHandle* h) {
LRUHandle** ptr = FindPointer(h);
LRUHandle** ptr = FindPointer(h->key(), h->hash);
LRUHandle* old = *ptr;
h->next_hash = (old == NULL ? NULL : old->next_hash);
*ptr = h;
@ -74,8 +75,8 @@ class HandleTable {
return old;
}
LRUHandle* Remove(LRUHandle* h) {
LRUHandle** ptr = FindPointer(h);
LRUHandle* Remove(const Slice& key, uint32_t hash) {
LRUHandle** ptr = FindPointer(key, hash);
LRUHandle* result = *ptr;
if (result != NULL) {
*ptr = result->next_hash;
@ -92,13 +93,12 @@ class HandleTable {
LRUHandle** list_;
// Return a pointer to slot that points to a cache entry that
// matches *h. If there is no such cache entry, return a pointer to
// the trailing slot in the corresponding linked list.
LRUHandle** FindPointer(LRUHandle* h) {
Slice key = h->key();
uint32_t hash = Hash(key.data(), key.size(), 0);
// matches key/hash. If there is no such cache entry, return a
// pointer to the trailing slot in the corresponding linked list.
LRUHandle** FindPointer(const Slice& key, uint32_t hash) {
LRUHandle** ptr = &list_[hash & (length_ - 1)];
while (*ptr != NULL && key != (*ptr)->key()) {
while (*ptr != NULL &&
((*ptr)->hash != hash || key != (*ptr)->key())) {
ptr = &(*ptr)->next_hash;
}
return ptr;
@ -117,7 +117,7 @@ class HandleTable {
while (h != NULL) {
LRUHandle* next = h->next_hash;
Slice key = h->key();
uint32_t hash = Hash(key.data(), key.size(), 0);
uint32_t hash = h->hash;
LRUHandle** ptr = &new_list[hash & (new_length - 1)];
h->next_hash = *ptr;
*ptr = h;
@ -132,26 +132,30 @@ class HandleTable {
}
};
class LRUCache : public Cache {
// A single shard of sharded cache.
class LRUCache {
public:
explicit LRUCache(size_t capacity);
virtual ~LRUCache();
LRUCache();
~LRUCache();
virtual Handle* Insert(const Slice& key, void* value, size_t charge,
// Separate from constructor so caller can easily make an array of LRUCache
void SetCapacity(size_t capacity) { capacity_ = capacity; }
// Like Cache methods, but with an extra "hash" parameter.
Cache::Handle* Insert(const Slice& key, uint32_t hash,
void* value, size_t charge,
void (*deleter)(const Slice& key, void* value));
virtual Handle* Lookup(const Slice& key);
virtual void Release(Handle* handle);
virtual void* Value(Handle* handle);
virtual void Erase(const Slice& key);
virtual uint64_t NewId();
Cache::Handle* Lookup(const Slice& key, uint32_t hash);
void Release(Cache::Handle* handle);
void Erase(const Slice& key, uint32_t hash);
private:
void LRU_Remove(LRUHandle* e);
void LRU_Append(LRUHandle* e);
void Unref(LRUHandle* e);
// Constructor parameters
const size_t capacity_;
// Initialized before use.
size_t capacity_;
// mutex_ protects the following state.
port::Mutex mutex_;
@ -165,9 +169,8 @@ class LRUCache : public Cache {
HandleTable table_;
};
LRUCache::LRUCache(size_t capacity)
: capacity_(capacity),
usage_(0),
LRUCache::LRUCache()
: usage_(0),
last_id_(0) {
// Make empty circular linked list
lru_.next = &lru_;
@ -206,31 +209,24 @@ void LRUCache::LRU_Append(LRUHandle* e) {
e->next->prev = e;
}
Cache::Handle* LRUCache::Lookup(const Slice& key) {
Cache::Handle* LRUCache::Lookup(const Slice& key, uint32_t hash) {
MutexLock l(&mutex_);
LRUHandle dummy;
dummy.next = &dummy;
dummy.value = const_cast<Slice*>(&key);
LRUHandle* e = table_.Lookup(&dummy);
LRUHandle* e = table_.Lookup(key, hash);
if (e != NULL) {
e->refs++;
LRU_Remove(e);
LRU_Append(e);
}
return reinterpret_cast<Handle*>(e);
return reinterpret_cast<Cache::Handle*>(e);
}
void* LRUCache::Value(Handle* handle) {
return reinterpret_cast<LRUHandle*>(handle)->value;
}
void LRUCache::Release(Handle* handle) {
void LRUCache::Release(Cache::Handle* handle) {
MutexLock l(&mutex_);
Unref(reinterpret_cast<LRUHandle*>(handle));
}
Cache::Handle* LRUCache::Insert(const Slice& key, void* value, size_t charge,
Cache::Handle* LRUCache::Insert(
const Slice& key, uint32_t hash, void* value, size_t charge,
void (*deleter)(const Slice& key, void* value)) {
MutexLock l(&mutex_);
@ -240,6 +236,7 @@ Cache::Handle* LRUCache::Insert(const Slice& key, void* value, size_t charge,
e->deleter = deleter;
e->charge = charge;
e->key_length = key.size();
e->hash = hash;
e->refs = 2; // One from LRUCache, one for the returned handle
memcpy(e->key_data, key.data(), key.size());
LRU_Append(e);
@ -254,35 +251,77 @@ Cache::Handle* LRUCache::Insert(const Slice& key, void* value, size_t charge,
while (usage_ > capacity_ && lru_.next != &lru_) {
LRUHandle* old = lru_.next;
LRU_Remove(old);
table_.Remove(old);
table_.Remove(old->key(), old->hash);
Unref(old);
}
return reinterpret_cast<Handle*>(e);
return reinterpret_cast<Cache::Handle*>(e);
}
void LRUCache::Erase(const Slice& key) {
void LRUCache::Erase(const Slice& key, uint32_t hash) {
MutexLock l(&mutex_);
LRUHandle dummy;
dummy.next = &dummy;
dummy.value = const_cast<Slice*>(&key);
LRUHandle* e = table_.Remove(&dummy);
LRUHandle* e = table_.Remove(key, hash);
if (e != NULL) {
LRU_Remove(e);
Unref(e);
}
}
uint64_t LRUCache::NewId() {
MutexLock l(&mutex_);
static const int kNumShardBits = 4;
static const int kNumShards = 1 << kNumShardBits;
class ShardedLRUCache : public Cache {
private:
LRUCache shard_[kNumShards];
port::Mutex id_mutex_;
uint64_t last_id_;
static inline uint32_t HashSlice(const Slice& s) {
return Hash(s.data(), s.size(), 0);
}
static uint32_t Shard(uint32_t hash) {
return hash >> (32 - kNumShardBits);
}
public:
explicit ShardedLRUCache(size_t capacity) {
const size_t per_shard = (capacity + (kNumShards - 1)) / kNumShards;
for (int s = 0; s < kNumShards; s++) {
shard_[s].SetCapacity(per_shard);
}
}
virtual ~ShardedLRUCache() { }
virtual Handle* Insert(const Slice& key, void* value, size_t charge,
void (*deleter)(const Slice& key, void* value)) {
const uint32_t hash = HashSlice(key);
return shard_[Shard(hash)].Insert(key, hash, value, charge, deleter);
}
virtual Handle* Lookup(const Slice& key) {
const uint32_t hash = HashSlice(key);
return shard_[Shard(hash)].Lookup(key, hash);
}
virtual void Release(Handle* handle) {
LRUHandle* h = reinterpret_cast<LRUHandle*>(handle);
shard_[Shard(h->hash)].Release(handle);
}
virtual void Erase(const Slice& key) {
const uint32_t hash = HashSlice(key);
shard_[Shard(hash)].Erase(key, hash);
}
virtual void* Value(Handle* handle) {
return reinterpret_cast<LRUHandle*>(handle)->value;
}
virtual uint64_t NewId() {
MutexLock l(&id_mutex_);
return ++(last_id_);
}
};
} // end anonymous namespace
Cache* NewLRUCache(size_t capacity) {
return new LRUCache(capacity);
return new ShardedLRUCache(capacity);
}
}

39
util/cache_test.cc
Unescape View File

@ -32,7 +32,7 @@ class CacheTest {
current_->deleted_values_.push_back(DecodeValue(v));
}
static const int kCacheSize = 100;
static const int kCacheSize = 1000;
std::vector<int> deleted_keys_;
std::vector<int> deleted_values_;
Cache* cache_;
@ -137,23 +137,40 @@ TEST(CacheTest, EvictionPolicy) {
Insert(200, 201);
// Frequently used entry must be kept around
for (int i = 0; i < kCacheSize; i++) {
for (int i = 0; i < kCacheSize + 100; i++) {
Insert(1000+i, 2000+i);
ASSERT_EQ(2000+i, Lookup(1000+i));
ASSERT_EQ(101, Lookup(100));
}
ASSERT_EQ(101, Lookup(100));
ASSERT_EQ(2, deleted_keys_.size());
ASSERT_EQ(200, deleted_keys_[0]);
ASSERT_EQ(201, deleted_values_[0]);
ASSERT_EQ(-1, Lookup(200));
}
TEST(CacheTest, HeavyEntry) {
Insert(100, 101);
Insert(200, 201, kCacheSize);
ASSERT_EQ(1, deleted_keys_.size());
ASSERT_EQ(100, deleted_keys_[0]);
ASSERT_EQ(101, deleted_values_[0]);
TEST(CacheTest, HeavyEntries) {
// Add a bunch of light and heavy entries and then count the combined
// size of items still in the cache, which must be approximately the
// same as the total capacity.
const int kLight = 1;
const int kHeavy = 10;
int added = 0;
int index = 0;
while (added < 2*kCacheSize) {
const int weight = (index & 1) ? kLight : kHeavy;
Insert(index, 1000+index, weight);
added += weight;
index++;
}
int cached_weight = 0;
for (int i = 0; i < index; i++) {
const int weight = (i & 1 ? kLight : kHeavy);
int r = Lookup(i);
if (r >= 0) {
cached_weight += weight;
ASSERT_EQ(1000+i, r);
}
}
ASSERT_LE(cached_weight, kCacheSize + kCacheSize/10);
}
TEST(CacheTest, NewId) {

11
util/histogram.cc
Unescape View File

@ -55,6 +55,17 @@ void Histogram::Add(double value) {
sum_squares_ += (value * value);
}
void Histogram::Merge(const Histogram& other) {
if (other.min_ < min_) min_ = other.min_;
if (other.max_ > max_) max_ = other.max_;
num_ += other.num_;
sum_ += other.sum_;
sum_squares_ += other.sum_squares_;
for (int b = 0; b < kNumBuckets; b++) {
buckets_[b] += other.buckets_[b];
}
}
double Histogram::Median() const {
return Percentile(50.0);
}

1
util/histogram.h
Unescape View File

@ -16,6 +16,7 @@ class Histogram {
void Clear();
void Add(double value);
void Merge(const Histogram& other);
std::string ToString() const;

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