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XOY-Leveldb
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XOY-Leveldb/db/db_bench.cc

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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include "db/db_impl.h"
#include "db/version_set.h"
#include "leveldb/cache.h"
#include "leveldb/db.h"
#include "leveldb/env.h"
#include "leveldb/write_batch.h"
#include "port/port.h"
#include "util/crc32c.h"
#include "util/histogram.h"
#include "util/mutexlock.h"
#include "util/random.h"
#include "util/testutil.h"
// Comma-separated list of operations to run in the specified order
// Actual benchmarks:
// fillseq -- write N values in sequential key order in async mode
// fillrandom -- write N values in random key order in async mode
// overwrite -- overwrite N values in random key order in async mode
// fillsync -- write N/100 values in random key order in sync mode
// fill100K -- write N/1000 100K values in random order in async mode
// readseq -- read N times sequentially
// readreverse -- read N times in reverse order
// readrandom -- read N times in random order
// readhot -- read N times in random order from 1% section of DB
// crc32c -- repeated crc32c of 4K of data
// acquireload -- load N*1000 times
// Meta operations:
// compact -- Compact the entire DB
// stats -- Print DB stats
// heapprofile -- Dump a heap profile (if supported by this port)
static const char* FLAGS_benchmarks =
"fillseq,"
"fillsync,"
"fillrandom,"
"overwrite,"
"readrandom,"
"readrandom," // Extra run to allow previous compactions to quiesce
"readseq,"
"readreverse,"
"compact,"
"readrandom,"
"readseq,"
"readreverse,"
"fill100K,"
"crc32c,"
"snappycomp,"
"snappyuncomp,"
"acquireload,"
;
// Number of key/values to place in database
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;
// Arrange to generate values that shrink to this fraction of
// their original size after compression
static double FLAGS_compression_ratio = 0.5;
// Print histogram of operation timings
static bool FLAGS_histogram = false;
// Number of bytes to buffer in memtable before compacting
// (initialized to default value by "main")
static int FLAGS_write_buffer_size = 0;
// Number of bytes to use as a cache of uncompressed data.
// Negative means use default settings.
static int FLAGS_cache_size = -1;
// Maximum number of files to keep open at the same time (use default if == 0)
static int FLAGS_open_files = 0;
// If true, do not destroy the existing database. If you set this
// flag and also specify a benchmark that wants a fresh database, that
// benchmark will fail.
static bool FLAGS_use_existing_db = false;
// Use the db with the following name.
static const char* FLAGS_db = "/tmp/dbbench";
namespace leveldb {
namespace {
// Helper for quickly generating random data.
class RandomGenerator {
private:
std::string data_;
int pos_;
public:
RandomGenerator() {
// We use a limited amount of data over and over again and ensure
// that it is larger than the compression window (32KB), and also
// large enough to serve all typical value sizes we want to write.
Random rnd(301);
std::string piece;
while (data_.size() < 1048576) {
// Add a short fragment that is as compressible as specified
// by FLAGS_compression_ratio.
test::CompressibleString(&rnd, FLAGS_compression_ratio, 100, &piece);
data_.append(piece);
}
pos_ = 0;
}
Slice Generate(int len) {
if (pos_ + len > data_.size()) {
pos_ = 0;
assert(len < data_.size());
}
pos_ += len;
return Slice(data_.data() + pos_ - len, len);
}
};
static Slice TrimSpace(Slice s) {
int start = 0;
while (start < s.size() && isspace(s[start])) {
start++;
}
int limit = s.size();
while (limit > start && isspace(s[limit-1])) {
limit--;
}
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 {
private:
Cache* cache_;
DB* db_;
int num_;
int value_size_;
int entries_per_batch_;
WriteOptions write_options_;
int reads_;
int heap_counter_;
void PrintHeader() {
const int kKeySize = 16;
PrintEnvironment();
fprintf(stdout, "Keys: %d bytes each\n", kKeySize);
fprintf(stdout, "Values: %d bytes each (%d bytes after compression)\n",
FLAGS_value_size,
static_cast<int>(FLAGS_value_size * FLAGS_compression_ratio + 0.5));
fprintf(stdout, "Entries: %d\n", num_);
fprintf(stdout, "RawSize: %.1f MB (estimated)\n",
((static_cast<int64_t>(kKeySize + FLAGS_value_size) * num_)
/ 1048576.0));
fprintf(stdout, "FileSize: %.1f MB (estimated)\n",
(((kKeySize + FLAGS_value_size * FLAGS_compression_ratio) * num_)
/ 1048576.0));
PrintWarnings();
fprintf(stdout, "------------------------------------------------\n");
}
void PrintWarnings() {
#if defined(__GNUC__) && !defined(__OPTIMIZE__)
fprintf(stdout,
"WARNING: Optimization is disabled: benchmarks unnecessarily slow\n"
);
#endif
#ifndef NDEBUG
fprintf(stdout,
"WARNING: Assertions are enabled; benchmarks unnecessarily slow\n");
#endif
// See if snappy is working by attempting to compress a compressible string
const char text[] = "yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy";
std::string compressed;
if (!port::Snappy_Compress(text, sizeof(text), &compressed)) {
fprintf(stdout, "WARNING: Snappy compression is not enabled\n");
} else if (compressed.size() >= sizeof(text)) {
fprintf(stdout, "WARNING: Snappy compression is not effective\n");
}
}
void PrintEnvironment() {
fprintf(stderr, "LevelDB: version %d.%d\n",
kMajorVersion, kMinorVersion);
#if defined(__linux)
time_t now = time(NULL);
fprintf(stderr, "Date: %s", ctime(&now)); // ctime() adds newline
FILE* cpuinfo = fopen("/proc/cpuinfo", "r");
if (cpuinfo != NULL) {
char line[1000];
int num_cpus = 0;
std::string cpu_type;
std::string cache_size;
while (fgets(line, sizeof(line), cpuinfo) != NULL) {
const char* sep = strchr(line, ':');
if (sep == NULL) {
continue;
}
Slice key = TrimSpace(Slice(line, sep - 1 - line));
Slice val = TrimSpace(Slice(sep + 1));
if (key == "model name") {
++num_cpus;
cpu_type = val.ToString();
} else if (key == "cache size") {
cache_size = val.ToString();
}
}
fclose(cpuinfo);
fprintf(stderr, "CPU: %d * %s\n", num_cpus, cpu_type.c_str());
fprintf(stderr, "CPUCache: %s\n", cache_size.c_str());
}
#endif
}
public:
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) {
std::vector<std::string> files;
Env::Default()->GetChildren(FLAGS_db, &files);
for (int i = 0; i < files.size(); i++) {
if (Slice(files[i]).starts_with("heap-")) {
Env::Default()->DeleteFile(std::string(FLAGS_db) + "/" + files[i]);
}
}
if (!FLAGS_use_existing_db) {
DestroyDB(FLAGS_db, Options());
}
}
~Benchmark() {
delete db_;
delete cache_;
}
void Run() {
PrintHeader();
Open();
const char* benchmarks = FLAGS_benchmarks;
while (benchmarks != NULL) {
const char* sep = strchr(benchmarks, ',');
Slice name;
if (sep == NULL) {
name = benchmarks;
benchmarks = NULL;
} else {
name = Slice(benchmarks, sep - benchmarks);
benchmarks = sep + 1;
}
// 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;
if (name == Slice("fillseq")) {
fresh_db = true;
method = &Benchmark::WriteSeq;
} else if (name == Slice("fillbatch")) {
fresh_db = true;
entries_per_batch_ = 1000;
method = &Benchmark::WriteSeq;
} else if (name == Slice("fillrandom")) {
fresh_db = true;
method = &Benchmark::WriteRandom;
} else if (name == Slice("overwrite")) {
fresh_db = false;
method = &Benchmark::WriteRandom;
} else if (name == Slice("fillsync")) {
fresh_db = true;
num_ /= 1000;
write_options_.sync = true;
method = &Benchmark::WriteRandom;
} else if (name == Slice("fill100K")) {
fresh_db = true;
num_ /= 1000;
value_size_ = 100 * 1000;
method = &Benchmark::WriteRandom;
} else if (name == Slice("readseq")) {
method = &Benchmark::ReadSequential;
} else if (name == Slice("readreverse")) {
method = &Benchmark::ReadReverse;
} else if (name == Slice("readrandom")) {
method = &Benchmark::ReadRandom;
} else if (name == Slice("readhot")) {
method = &Benchmark::ReadHot;
} else if (name == Slice("readrandomsmall")) {
reads_ /= 1000;
method = &Benchmark::ReadRandom;
} else if (name == Slice("compact")) {
method = &Benchmark::Compact;
} else if (name == Slice("crc32c")) {
method = &Benchmark::Crc32c;
} else if (name == Slice("acquireload")) {
method = &Benchmark::AcquireLoad;
} else if (name == Slice("snappycomp")) {
method = &Benchmark::SnappyCompress;
} else if (name == Slice("snappyuncomp")) {
method = &Benchmark::SnappyUncompress;
} else if (name == Slice("heapprofile")) {
HeapProfile();
} else if (name == Slice("stats")) {
PrintStats();
} else {
if (name != Slice()) { // No error message for empty name
fprintf(stderr, "unknown benchmark '%s'\n", name.ToString().c_str());
}
}
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:
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);
thread->stats.FinishedSingleOp();
bytes += size;
}
// Print so result is not dead
fprintf(stderr, "... crc=0x%x\r", static_cast<unsigned int>(crc));
thread->stats.AddBytes(bytes);
thread->stats.AddMessage(label);
}
void AcquireLoad(ThreadState* thread) {
int dummy;
port::AtomicPointer ap(&dummy);
int count = 0;
void *ptr = NULL;
thread->stats.AddMessage("(each op is 1000 loads)");
while (count < 100000) {
for (int i = 0; i < 1000; i++) {
ptr = ap.Acquire_Load();
}
count++;
thread->stats.FinishedSingleOp();
}
if (ptr == NULL) exit(1); // Disable unused variable warning.
}
void SnappyCompress(ThreadState* thread) {
RandomGenerator gen;
Slice input = gen.Generate(Options().block_size);
int64_t bytes = 0;
int64_t produced = 0;
bool ok = true;
std::string compressed;
while (ok && bytes < 1024 * 1048576) { // Compress 1G
ok = port::Snappy_Compress(input.data(), input.size(), &compressed);
produced += compressed.size();
bytes += input.size();
thread->stats.FinishedSingleOp();
}
if (!ok) {
thread->stats.AddMessage("(snappy failure)");
} else {
char buf[100];
snprintf(buf, sizeof(buf), "(output: %.1f%%)",
(produced * 100.0) / bytes);
thread->stats.AddMessage(buf);
thread->stats.AddBytes(bytes);
}
}
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;
char* uncompressed = new char[input.size()];
while (ok && bytes < 1024 * 1048576) { // Compress 1G
ok = port::Snappy_Uncompress(compressed.data(), compressed.size(),
uncompressed);
bytes += input.size();
thread->stats.FinishedSingleOp();
}
delete[] uncompressed;
if (!ok) {
thread->stats.AddMessage("(snappy failure)");
} else {
thread->stats.AddBytes(bytes);
}
}
void Open() {
assert(db_ == NULL);
Options options;
options.create_if_missing = !FLAGS_use_existing_db;
options.block_cache = cache_;
options.write_buffer_size = FLAGS_write_buffer_size;
Status s = DB::Open(options, FLAGS_db, &db_);
if (!s.ok()) {
fprintf(stderr, "open error: %s\n", s.ToString().c_str());
exit(1);
}
}
void WriteSeq(ThreadState* thread) {
DoWrite(thread, true);
}
void WriteRandom(ThreadState* thread) {
DoWrite(thread, false);
}
void DoWrite(ThreadState* thread, bool seq) {
if (num_ != FLAGS_num) {
char msg[100];
snprintf(msg, sizeof(msg), "(%d ops)", num_);
thread->stats.AddMessage(msg);
}
RandomGenerator gen;
WriteBatch batch;
Status s;
std::string val;
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 = 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);
thread->stats.FinishedSingleOp();
}
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(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();
thread->stats.FinishedSingleOp();
++i;
}
delete iter;
thread->stats.AddBytes(bytes);
}
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();
thread->stats.FinishedSingleOp();
++i;
}
delete iter;
thread->stats.AddBytes(bytes);
}
void ReadRandom(ThreadState* thread) {
ReadOptions options;
std::string value;
for (int i = 0; i < reads_; i++) {
char key[100];
const int k = thread->rand.Next() % FLAGS_num;
snprintf(key, sizeof(key), "%016d", k);
db_->Get(options, key, &value);
thread->stats.FinishedSingleOp();
}
}
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 = thread->rand.Next() % range;
snprintf(key, sizeof(key), "%016d", k);
db_->Get(options, key, &value);
thread->stats.FinishedSingleOp();
}
}
void Compact(ThreadState* thread) {
DBImpl* dbi = reinterpret_cast<DBImpl*>(db_);
dbi->TEST_CompactMemTable();
int max_level_with_files = 1;
for (int level = 1; level < config::kNumLevels; level++) {
std::string property;
char name[100];
snprintf(name, sizeof(name), "leveldb.num-files-at-level%d", level);
if (db_->GetProperty(name, &property) && atoi(property.c_str()) > 0) {
max_level_with_files = level;
}
}
for (int level = 0; level < max_level_with_files; level++) {
dbi->TEST_CompactRange(level, "", "~");
}
}
void PrintStats() {
std::string stats;
if (!db_->GetProperty("leveldb.stats", &stats)) {
stats = "(failed)";
}
fprintf(stdout, "\n%s\n", stats.c_str());
}
static void WriteToFile(void* arg, const char* buf, int n) {
reinterpret_cast<WritableFile*>(arg)->Append(Slice(buf, n));
}
void HeapProfile() {
char fname[100];
snprintf(fname, sizeof(fname), "%s/heap-%04d", FLAGS_db, ++heap_counter_);
WritableFile* file;
Status s = Env::Default()->NewWritableFile(fname, &file);
if (!s.ok()) {
fprintf(stderr, "%s\n", s.ToString().c_str());
return;
}
bool ok = port::GetHeapProfile(WriteToFile, file);
delete file;
if (!ok) {
fprintf(stderr, "heap profiling not supported\n");
Env::Default()->DeleteFile(fname);
}
}
};
}
int main(int argc, char** argv) {
FLAGS_write_buffer_size = leveldb::Options().write_buffer_size;
FLAGS_open_files = leveldb::Options().max_open_files;
for (int i = 1; i < argc; i++) {
double d;
int n;
char junk;
if (leveldb::Slice(argv[i]).starts_with("--benchmarks=")) {
FLAGS_benchmarks = argv[i] + strlen("--benchmarks=");
} else if (sscanf(argv[i], "--compression_ratio=%lf%c", &d, &junk) == 1) {
FLAGS_compression_ratio = d;
} else if (sscanf(argv[i], "--histogram=%d%c", &n, &junk) == 1 &&
(n == 0 || n == 1)) {
FLAGS_histogram = n;
} else if (sscanf(argv[i], "--use_existing_db=%d%c", &n, &junk) == 1 &&
(n == 0 || n == 1)) {
FLAGS_use_existing_db = n;
} else if (sscanf(argv[i], "--num=%d%c", &n, &junk) == 1) {
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) {
FLAGS_write_buffer_size = n;
} else if (sscanf(argv[i], "--cache_size=%d%c", &n, &junk) == 1) {
FLAGS_cache_size = n;
} else if (sscanf(argv[i], "--open_files=%d%c", &n, &junk) == 1) {
FLAGS_open_files = n;
} else if (strncmp(argv[i], "--db=", 5) == 0) {
FLAGS_db = argv[i] + 5;
} else {
fprintf(stderr, "Invalid flag '%s'\n", argv[i]);
exit(1);
}
}
leveldb::Benchmark benchmark;
benchmark.Run();
return 0;
}