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rocksdb/cache/cache_bench_tool.cc

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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#ifdef GFLAGS
#include <cinttypes>
#include <cstdio>
#include <limits>
#include <set>
#include <sstream>
#include "monitoring/histogram.h"
#include "port/port.h"
#include "rocksdb/cache.h"
#include "rocksdb/convenience.h"
#include "rocksdb/db.h"
#include "rocksdb/env.h"
#include "rocksdb/secondary_cache.h"
#include "rocksdb/system_clock.h"
#include "table/block_based/cachable_entry.h"
#include "util/coding.h"
#include "util/gflags_compat.h"
#include "util/hash.h"
#include "util/mutexlock.h"
#include "util/random.h"
#include "util/stop_watch.h"
#include "util/string_util.h"
using GFLAGS_NAMESPACE::ParseCommandLineFlags;
static constexpr uint32_t KiB = uint32_t{1} << 10;
static constexpr uint32_t MiB = KiB << 10;
static constexpr uint64_t GiB = MiB << 10;
DEFINE_uint32(threads, 16, "Number of concurrent threads to run.");
DEFINE_uint64(cache_size, 1 * GiB,
"Number of bytes to use as a cache of uncompressed data.");
DEFINE_uint32(num_shard_bits, 6, "shard_bits.");
DEFINE_double(resident_ratio, 0.25,
"Ratio of keys fitting in cache to keyspace.");
DEFINE_uint64(ops_per_thread, 2000000U, "Number of operations per thread.");
DEFINE_uint32(value_bytes, 8 * KiB, "Size of each value added.");
DEFINE_uint32(skew, 5, "Degree of skew in key selection");
DEFINE_bool(populate_cache, true, "Populate cache before operations");
DEFINE_uint32(lookup_insert_percent, 87,
"Ratio of lookup (+ insert on not found) to total workload "
"(expressed as a percentage)");
DEFINE_uint32(insert_percent, 2,
"Ratio of insert to total workload (expressed as a percentage)");
DEFINE_uint32(lookup_percent, 10,
"Ratio of lookup to total workload (expressed as a percentage)");
DEFINE_uint32(erase_percent, 1,
"Ratio of erase to total workload (expressed as a percentage)");
DEFINE_bool(gather_stats, false,
"Whether to periodically simulate gathering block cache stats, "
"using one more thread.");
DEFINE_uint32(
gather_stats_sleep_ms, 1000,
"How many milliseconds to sleep between each gathering of stats.");
DEFINE_uint32(gather_stats_entries_per_lock, 256,
"For Cache::ApplyToAllEntries");
DEFINE_bool(skewed, false, "If true, skew the key access distribution");
#ifndef ROCKSDB_LITE
DEFINE_string(secondary_cache_uri, "",
"Full URI for creating a custom secondary cache object");
static class std::shared_ptr<ROCKSDB_NAMESPACE::SecondaryCache> secondary_cache;
#endif // ROCKSDB_LITE
DEFINE_bool(use_clock_cache, false, "");
namespace ROCKSDB_NAMESPACE {
class CacheBench;
namespace {
// State shared by all concurrent executions of the same benchmark.
class SharedState {
public:
explicit SharedState(CacheBench* cache_bench)
: cv_(&mu_),
num_initialized_(0),
start_(false),
num_done_(0),
cache_bench_(cache_bench) {}
~SharedState() {}
port::Mutex* GetMutex() { return &mu_; }
port::CondVar* GetCondVar() { return &cv_; }
CacheBench* GetCacheBench() const { return cache_bench_; }
void IncInitialized() { num_initialized_++; }
void IncDone() { num_done_++; }
bool AllInitialized() const { return num_initialized_ >= FLAGS_threads; }
bool AllDone() const { return num_done_ >= FLAGS_threads; }
void SetStart() { start_ = true; }
bool Started() const { return start_; }
private:
port::Mutex mu_;
port::CondVar cv_;
uint64_t num_initialized_;
bool start_;
uint64_t num_done_;
CacheBench* cache_bench_;
};
// Per-thread state for concurrent executions of the same benchmark.
struct ThreadState {
uint32_t tid;
Random64 rnd;
SharedState* shared;
HistogramImpl latency_ns_hist;
uint64_t duration_us = 0;
ThreadState(uint32_t index, SharedState* _shared)
: tid(index), rnd(1000 + index), shared(_shared) {}
};
struct KeyGen {
char key_data[27];
Slice GetRand(Random64& rnd, uint64_t max_key, int max_log) {
uint64_t key = 0;
if (!FLAGS_skewed) {
uint64_t raw = rnd.Next();
// Skew according to setting
for (uint32_t i = 0; i < FLAGS_skew; ++i) {
raw = std::min(raw, rnd.Next());
}
key = FastRange64(raw, max_key);
} else {
key = rnd.Skewed(max_log);
if (key > max_key) {
key -= max_key;
}
}
// Variable size and alignment
size_t off = key % 8;
key_data[0] = char{42};
EncodeFixed64(key_data + 1, key);
key_data[9] = char{11};
EncodeFixed64(key_data + 10, key);
key_data[18] = char{4};
EncodeFixed64(key_data + 19, key);
return Slice(&key_data[off], sizeof(key_data) - off);
}
};
char* createValue(Random64& rnd) {
char* rv = new char[FLAGS_value_bytes];
// Fill with some filler data, and take some CPU time
for (uint32_t i = 0; i < FLAGS_value_bytes; i += 8) {
EncodeFixed64(rv + i, rnd.Next());
}
return rv;
}
// Callbacks for secondary cache
size_t SizeFn(void* /*obj*/) { return FLAGS_value_bytes; }
Status SaveToFn(void* obj, size_t /*offset*/, size_t size, void* out) {
memcpy(out, obj, size);
return Status::OK();
}
// Different deleters to simulate using deleter to gather
// stats on the code origin and kind of cache entries.
void deleter1(const Slice& /*key*/, void* value) {
delete[] static_cast<char*>(value);
}
void deleter2(const Slice& /*key*/, void* value) {
delete[] static_cast<char*>(value);
}
void deleter3(const Slice& /*key*/, void* value) {
delete[] static_cast<char*>(value);
}
Cache::CacheItemHelper helper1(SizeFn, SaveToFn, deleter1);
Cache::CacheItemHelper helper2(SizeFn, SaveToFn, deleter2);
Cache::CacheItemHelper helper3(SizeFn, SaveToFn, deleter3);
} // namespace
class CacheBench {
static constexpr uint64_t kHundredthUint64 =
std::numeric_limits<uint64_t>::max() / 100U;
public:
CacheBench()
: max_key_(static_cast<uint64_t>(FLAGS_cache_size / FLAGS_resident_ratio /
FLAGS_value_bytes)),
lookup_insert_threshold_(kHundredthUint64 *
FLAGS_lookup_insert_percent),
insert_threshold_(lookup_insert_threshold_ +
kHundredthUint64 * FLAGS_insert_percent),
lookup_threshold_(insert_threshold_ +
kHundredthUint64 * FLAGS_lookup_percent),
erase_threshold_(lookup_threshold_ +
kHundredthUint64 * FLAGS_erase_percent),
skewed_(FLAGS_skewed) {
if (erase_threshold_ != 100U * kHundredthUint64) {
fprintf(stderr, "Percentages must add to 100.\n");
exit(1);
}
max_log_ = 0;
if (skewed_) {
uint64_t max_key = max_key_;
while (max_key >>= 1) max_log_++;
if (max_key > (static_cast<uint64_t>(1) << max_log_)) max_log_++;
}
if (FLAGS_use_clock_cache) {
cache_ = NewClockCache(FLAGS_cache_size, FLAGS_num_shard_bits);
if (!cache_) {
fprintf(stderr, "Clock cache not supported.\n");
exit(1);
}
} else {
LRUCacheOptions opts(FLAGS_cache_size, FLAGS_num_shard_bits, false, 0.5);
#ifndef ROCKSDB_LITE
if (!FLAGS_secondary_cache_uri.empty()) {
Status s = SecondaryCache::CreateFromString(
ConfigOptions(), FLAGS_secondary_cache_uri, &secondary_cache);
if (secondary_cache == nullptr) {
fprintf(
stderr,
"No secondary cache registered matching string: %s status=%s\n",
FLAGS_secondary_cache_uri.c_str(), s.ToString().c_str());
exit(1);
}
opts.secondary_cache = secondary_cache;
}
#endif // ROCKSDB_LITE
cache_ = NewLRUCache(opts);
}
}
~CacheBench() {}
void PopulateCache() {
Random64 rnd(1);
KeyGen keygen;
for (uint64_t i = 0; i < 2 * FLAGS_cache_size; i += FLAGS_value_bytes) {
cache_->Insert(keygen.GetRand(rnd, max_key_, max_log_), createValue(rnd),
&helper1, FLAGS_value_bytes);
}
}
bool Run() {
const auto clock = SystemClock::Default().get();
PrintEnv();
SharedState shared(this);
std::vector<std::unique_ptr<ThreadState> > threads(FLAGS_threads);
for (uint32_t i = 0; i < FLAGS_threads; i++) {
threads[i].reset(new ThreadState(i, &shared));
std::thread(ThreadBody, threads[i].get()).detach();
}
HistogramImpl stats_hist;
std::string stats_report;
std::thread stats_thread(StatsBody, &shared, &stats_hist, &stats_report);
uint64_t start_time;
{
MutexLock l(shared.GetMutex());
while (!shared.AllInitialized()) {
shared.GetCondVar()->Wait();
}
// Record start time
start_time = clock->NowMicros();
// Start all threads
shared.SetStart();
shared.GetCondVar()->SignalAll();
// Wait threads to complete
while (!shared.AllDone()) {
shared.GetCondVar()->Wait();
}
}
// Stats gathering is considered background work. This time measurement
// is for foreground work, and not really ideal for that. See below.
uint64_t end_time = clock->NowMicros();
stats_thread.join();
// Wall clock time - includes idle time if threads
// finish at different times (not ideal).
double elapsed_secs = static_cast<double>(end_time - start_time) * 1e-6;
uint32_t ops_per_sec = static_cast<uint32_t>(
1.0 * FLAGS_threads * FLAGS_ops_per_thread / elapsed_secs);
printf("Complete in %.3f s; Rough parallel ops/sec = %u\n", elapsed_secs,
ops_per_sec);
// Total time in each thread (more accurate throughput measure)
elapsed_secs = 0;
for (uint32_t i = 0; i < FLAGS_threads; i++) {
elapsed_secs += threads[i]->duration_us * 1e-6;
}
ops_per_sec = static_cast<uint32_t>(1.0 * FLAGS_threads *
FLAGS_ops_per_thread / elapsed_secs);
printf("Thread ops/sec = %u\n", ops_per_sec);
printf("\nOperation latency (ns):\n");
HistogramImpl combined;
for (uint32_t i = 0; i < FLAGS_threads; i++) {
combined.Merge(threads[i]->latency_ns_hist);
}
printf("%s", combined.ToString().c_str());
if (FLAGS_gather_stats) {
printf("\nGather stats latency (us):\n");
printf("%s", stats_hist.ToString().c_str());
}
printf("\n%s", stats_report.c_str());
return true;
}
private:
std::shared_ptr<Cache> cache_;
const uint64_t max_key_;
// Cumulative thresholds in the space of a random uint64_t
const uint64_t lookup_insert_threshold_;
const uint64_t insert_threshold_;
const uint64_t lookup_threshold_;
const uint64_t erase_threshold_;
const bool skewed_;
int max_log_;
// A benchmark version of gathering stats on an active block cache by
// iterating over it. The primary purpose is to measure the impact of
// gathering stats with ApplyToAllEntries on throughput- and
// latency-sensitive Cache users. Performance of stats gathering is
// also reported. The last set of gathered stats is also reported, for
// manual sanity checking for logical errors or other unexpected
// behavior of cache_bench or the underlying Cache.
static void StatsBody(SharedState* shared, HistogramImpl* stats_hist,
std::string* stats_report) {
if (!FLAGS_gather_stats) {
return;
}
const auto clock = SystemClock::Default().get();
uint64_t total_key_size = 0;
uint64_t total_charge = 0;
uint64_t total_entry_count = 0;
std::set<Cache::DeleterFn> deleters;
StopWatchNano timer(clock);
for (;;) {
uint64_t time;
time = clock->NowMicros();
uint64_t deadline = time + uint64_t{FLAGS_gather_stats_sleep_ms} * 1000;
{
MutexLock l(shared->GetMutex());
for (;;) {
if (shared->AllDone()) {
std::ostringstream ostr;
ostr << "Most recent cache entry stats:\n"
<< "Number of entries: " << total_entry_count << "\n"
<< "Total charge: " << BytesToHumanString(total_charge) << "\n"
<< "Average key size: "
<< (1.0 * total_key_size / total_entry_count) << "\n"
<< "Average charge: "
<< BytesToHumanString(static_cast<uint64_t>(
1.0 * total_charge / total_entry_count))
<< "\n"
<< "Unique deleters: " << deleters.size() << "\n";
*stats_report = ostr.str();
return;
}
if (clock->NowMicros() >= deadline) {
break;
}
uint64_t diff = deadline - std::min(clock->NowMicros(), deadline);
shared->GetCondVar()->TimedWait(diff + 1);
}
}
// Now gather stats, outside of mutex
total_key_size = 0;
total_charge = 0;
total_entry_count = 0;
deleters.clear();
auto fn = [&](const Slice& key, void* /*value*/, size_t charge,
Cache::DeleterFn deleter) {
total_key_size += key.size();
total_charge += charge;
++total_entry_count;
// Something slightly more expensive as in (future) stats by category
deleters.insert(deleter);
};
timer.Start();
Cache::ApplyToAllEntriesOptions opts;
opts.average_entries_per_lock = FLAGS_gather_stats_entries_per_lock;
shared->GetCacheBench()->cache_->ApplyToAllEntries(fn, opts);
stats_hist->Add(timer.ElapsedNanos() / 1000);
}
}
static void ThreadBody(ThreadState* thread) {
SharedState* shared = thread->shared;
{
MutexLock l(shared->GetMutex());
shared->IncInitialized();
if (shared->AllInitialized()) {
shared->GetCondVar()->SignalAll();
}
while (!shared->Started()) {
shared->GetCondVar()->Wait();
}
}
thread->shared->GetCacheBench()->OperateCache(thread);
{
MutexLock l(shared->GetMutex());
shared->IncDone();
if (shared->AllDone()) {
shared->GetCondVar()->SignalAll();
}
}
}
void OperateCache(ThreadState* thread) {
// To use looked-up values
uint64_t result = 0;
// To hold handles for a non-trivial amount of time
Cache::Handle* handle = nullptr;
KeyGen gen;
const auto clock = SystemClock::Default().get();
uint64_t start_time = clock->NowMicros();
StopWatchNano timer(clock);
for (uint64_t i = 0; i < FLAGS_ops_per_thread; i++) {
timer.Start();
Slice key = gen.GetRand(thread->rnd, max_key_, max_log_);
uint64_t random_op = thread->rnd.Next();
Cache::CreateCallback create_cb =
[](void* buf, size_t size, void** out_obj, size_t* charge) -> Status {
*out_obj = reinterpret_cast<void*>(new char[size]);
memcpy(*out_obj, buf, size);
*charge = size;
return Status::OK();
};
if (random_op < lookup_insert_threshold_) {
if (handle) {
cache_->Release(handle);
handle = nullptr;
}
// do lookup
handle = cache_->Lookup(key, &helper2, create_cb, Cache::Priority::LOW,
true);
if (handle) {
// do something with the data
result += NPHash64(static_cast<char*>(cache_->Value(handle)),
FLAGS_value_bytes);
} else {
// do insert
cache_->Insert(key, createValue(thread->rnd), &helper2,
FLAGS_value_bytes, &handle);
}
} else if (random_op < insert_threshold_) {
if (handle) {
cache_->Release(handle);
handle = nullptr;
}
// do insert
cache_->Insert(key, createValue(thread->rnd), &helper3,
FLAGS_value_bytes, &handle);
} else if (random_op < lookup_threshold_) {
if (handle) {
cache_->Release(handle);
handle = nullptr;
}
// do lookup
handle = cache_->Lookup(key, &helper2, create_cb, Cache::Priority::LOW,
true);
if (handle) {
// do something with the data
result += NPHash64(static_cast<char*>(cache_->Value(handle)),
FLAGS_value_bytes);
}
} else if (random_op < erase_threshold_) {
// do erase
cache_->Erase(key);
} else {
// Should be extremely unlikely (noop)
assert(random_op >= kHundredthUint64 * 100U);
}
thread->latency_ns_hist.Add(timer.ElapsedNanos());
}
if (handle) {
cache_->Release(handle);
handle = nullptr;
}
// Ensure computations on `result` are not optimized away.
if (result == 1) {
printf("You are extremely unlucky(2). Try again.\n");
exit(1);
}
thread->duration_us = clock->NowMicros() - start_time;
}
void PrintEnv() const {
printf("RocksDB version : %d.%d\n", kMajorVersion, kMinorVersion);
printf("Number of threads : %u\n", FLAGS_threads);
printf("Ops per thread : %" PRIu64 "\n", FLAGS_ops_per_thread);
printf("Cache size : %s\n",
BytesToHumanString(FLAGS_cache_size).c_str());
printf("Num shard bits : %u\n", FLAGS_num_shard_bits);
printf("Max key : %" PRIu64 "\n", max_key_);
printf("Resident ratio : %g\n", FLAGS_resident_ratio);
printf("Skew degree : %u\n", FLAGS_skew);
printf("Populate cache : %d\n", int{FLAGS_populate_cache});
printf("Lookup+Insert pct : %u%%\n", FLAGS_lookup_insert_percent);
printf("Insert percentage : %u%%\n", FLAGS_insert_percent);
printf("Lookup percentage : %u%%\n", FLAGS_lookup_percent);
printf("Erase percentage : %u%%\n", FLAGS_erase_percent);
std::ostringstream stats;
if (FLAGS_gather_stats) {
stats << "enabled (" << FLAGS_gather_stats_sleep_ms << "ms, "
<< FLAGS_gather_stats_entries_per_lock << "/lock)";
} else {
stats << "disabled";
}
printf("Gather stats : %s\n", stats.str().c_str());
printf("----------------------------\n");
}
};
int cache_bench_tool(int argc, char** argv) {
ParseCommandLineFlags(&argc, &argv, true);
if (FLAGS_threads <= 0) {
fprintf(stderr, "threads number <= 0\n");
exit(1);
}
ROCKSDB_NAMESPACE::CacheBench bench;
if (FLAGS_populate_cache) {
bench.PopulateCache();
printf("Population complete\n");
printf("----------------------------\n");
}
if (bench.Run()) {
return 0;
} else {
return 1;
}
} // namespace ROCKSDB_NAMESPACE
} // namespace ROCKSDB_NAMESPACE
#endif // GFLAGS
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