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rocksdb/utilities/simulator_cache/cache_simulator_test.cc
Maysam Yabandeh 638d239507 Charge block cache for cache internal usage (#5797) 
Summary:
For our default block cache, each additional entry has extra memory overhead. It include LRUHandle (72 bytes currently) and the cache key (two varint64, file id and offset). The usage is not negligible. For example for block_size=4k, the overhead accounts for an extra 2% memory usage for the cache. The patch charging the cache for the extra usage, reducing untracked memory usage outside block cache. The feature is enabled by default and can be disabled by passing kDontChargeCacheMetadata to the cache constructor.
This PR builds up on https://github.com/facebook/rocksdb/issues/4258
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5797

Test Plan:
- Existing tests are updated to either disable the feature when the test has too much dependency on the old way of accounting the usage or increasing the cache capacity to account for the additional charge of metadata.
- The Usage tests in cache_test.cc are augmented to test the cache usage under kFullChargeCacheMetadata.

Differential Revision: D17396833

Pulled By: maysamyabandeh

fbshipit-source-id: 7684ccb9f8a40ca595e4f5efcdb03623afea0c6f
2019-09-16 15:26:21 -07:00

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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).
#include "utilities/simulator_cache/cache_simulator.h"
#include <cstdlib>
#include "rocksdb/env.h"
#include "test_util/testharness.h"
#include "test_util/testutil.h"
namespace rocksdb {
namespace {
const std::string kBlockKeyPrefix = "test-block-";
const std::string kRefKeyPrefix = "test-get-";
const std::string kRefKeySequenceNumber = std::string(8, 'c');
const uint64_t kGetId = 1;
const uint64_t kGetBlockId = 100;
const uint64_t kCompactionBlockId = 1000;
const uint64_t kCacheSize = 1024 * 1024 * 1024;
const uint64_t kGhostCacheSize = 1024 * 1024;
} // namespace
class CacheSimulatorTest : public testing::Test {
public:
const size_t kNumBlocks = 5;
const size_t kValueSize = 1000;
CacheSimulatorTest() { env_ = rocksdb::Env::Default(); }
BlockCacheTraceRecord GenerateGetRecord(uint64_t getid) {
BlockCacheTraceRecord record;
record.block_type = TraceType::kBlockTraceDataBlock;
record.block_size = 4096;
record.block_key = kBlockKeyPrefix + std::to_string(kGetBlockId);
record.access_timestamp = env_->NowMicros();
record.cf_id = 0;
record.cf_name = "test";
record.caller = TableReaderCaller::kUserGet;
record.level = 6;
record.sst_fd_number = 0;
record.get_id = getid;
record.is_cache_hit = Boolean::kFalse;
record.no_insert = Boolean::kFalse;
record.referenced_key =
kRefKeyPrefix + std::to_string(kGetId) + kRefKeySequenceNumber;
record.referenced_key_exist_in_block = Boolean::kTrue;
record.referenced_data_size = 100;
record.num_keys_in_block = 300;
return record;
}
BlockCacheTraceRecord GenerateCompactionRecord() {
BlockCacheTraceRecord record;
record.block_type = TraceType::kBlockTraceDataBlock;
record.block_size = 4096;
record.block_key = kBlockKeyPrefix + std::to_string(kCompactionBlockId);
record.access_timestamp = env_->NowMicros();
record.cf_id = 0;
record.cf_name = "test";
record.caller = TableReaderCaller::kCompaction;
record.level = 6;
record.sst_fd_number = kCompactionBlockId;
record.is_cache_hit = Boolean::kFalse;
record.no_insert = Boolean::kTrue;
return record;
}
void AssertCache(std::shared_ptr<Cache> sim_cache,
const MissRatioStats& miss_ratio_stats,
uint64_t expected_usage, uint64_t expected_num_accesses,
uint64_t expected_num_misses,
std::vector<std::string> blocks,
std::vector<std::string> keys) {
EXPECT_EQ(expected_usage, sim_cache->GetUsage());
EXPECT_EQ(expected_num_accesses, miss_ratio_stats.total_accesses());
EXPECT_EQ(expected_num_misses, miss_ratio_stats.total_misses());
for (auto const& block : blocks) {
auto handle = sim_cache->Lookup(block);
EXPECT_NE(nullptr, handle);
sim_cache->Release(handle);
}
for (auto const& key : keys) {
std::string row_key = kRefKeyPrefix + key + kRefKeySequenceNumber;
auto handle =
sim_cache->Lookup("0_" + ExtractUserKey(row_key).ToString());
EXPECT_NE(nullptr, handle);
sim_cache->Release(handle);
}
}
Env* env_;
};
TEST_F(CacheSimulatorTest, GhostCache) {
const std::string key1 = "test1";
const std::string key2 = "test2";
std::unique_ptr<GhostCache> ghost_cache(new GhostCache(
NewLRUCache(/*capacity=*/kGhostCacheSize, /*num_shard_bits=*/1,
/*strict_capacity_limit=*/false,
/*high_pri_pool_ratio=*/0)));
EXPECT_FALSE(ghost_cache->Admit(key1));
EXPECT_TRUE(ghost_cache->Admit(key1));
EXPECT_TRUE(ghost_cache->Admit(key1));
EXPECT_FALSE(ghost_cache->Admit(key2));
EXPECT_TRUE(ghost_cache->Admit(key2));
}
TEST_F(CacheSimulatorTest, CacheSimulator) {
const BlockCacheTraceRecord& access = GenerateGetRecord(kGetId);
const BlockCacheTraceRecord& compaction_access = GenerateCompactionRecord();
std::shared_ptr<Cache> sim_cache =
NewLRUCache(/*capacity=*/kCacheSize, /*num_shard_bits=*/1,
/*strict_capacity_limit=*/false,
/*high_pri_pool_ratio=*/0);
std::unique_ptr<CacheSimulator> cache_simulator(
new CacheSimulator(nullptr, sim_cache));
cache_simulator->Access(access);
cache_simulator->Access(access);
ASSERT_EQ(2, cache_simulator->miss_ratio_stats().total_accesses());
ASSERT_EQ(50, cache_simulator->miss_ratio_stats().miss_ratio());
ASSERT_EQ(2, cache_simulator->miss_ratio_stats().user_accesses());
ASSERT_EQ(50, cache_simulator->miss_ratio_stats().user_miss_ratio());
cache_simulator->Access(compaction_access);
cache_simulator->Access(compaction_access);
ASSERT_EQ(4, cache_simulator->miss_ratio_stats().total_accesses());
ASSERT_EQ(75, cache_simulator->miss_ratio_stats().miss_ratio());
ASSERT_EQ(2, cache_simulator->miss_ratio_stats().user_accesses());
ASSERT_EQ(50, cache_simulator->miss_ratio_stats().user_miss_ratio());
cache_simulator->reset_counter();
ASSERT_EQ(0, cache_simulator->miss_ratio_stats().total_accesses());
ASSERT_EQ(-1, cache_simulator->miss_ratio_stats().miss_ratio());
auto handle = sim_cache->Lookup(access.block_key);
ASSERT_NE(nullptr, handle);
sim_cache->Release(handle);
handle = sim_cache->Lookup(compaction_access.block_key);
ASSERT_EQ(nullptr, handle);
}
TEST_F(CacheSimulatorTest, GhostCacheSimulator) {
const BlockCacheTraceRecord& access = GenerateGetRecord(kGetId);
std::unique_ptr<GhostCache> ghost_cache(new GhostCache(
NewLRUCache(/*capacity=*/kGhostCacheSize, /*num_shard_bits=*/1,
/*strict_capacity_limit=*/false,
/*high_pri_pool_ratio=*/0)));
std::unique_ptr<CacheSimulator> cache_simulator(new CacheSimulator(
std::move(ghost_cache),
NewLRUCache(/*capacity=*/kCacheSize, /*num_shard_bits=*/1,
/*strict_capacity_limit=*/false,
/*high_pri_pool_ratio=*/0)));
cache_simulator->Access(access);
cache_simulator->Access(access);
ASSERT_EQ(2, cache_simulator->miss_ratio_stats().total_accesses());
// Both of them will be miss since we have a ghost cache.
ASSERT_EQ(100, cache_simulator->miss_ratio_stats().miss_ratio());
}
TEST_F(CacheSimulatorTest, PrioritizedCacheSimulator) {
const BlockCacheTraceRecord& access = GenerateGetRecord(kGetId);
std::shared_ptr<Cache> sim_cache =
NewLRUCache(/*capacity=*/kCacheSize, /*num_shard_bits=*/1,
/*strict_capacity_limit=*/false,
/*high_pri_pool_ratio=*/0);
std::unique_ptr<PrioritizedCacheSimulator> cache_simulator(
new PrioritizedCacheSimulator(nullptr, sim_cache));
cache_simulator->Access(access);
cache_simulator->Access(access);
ASSERT_EQ(2, cache_simulator->miss_ratio_stats().total_accesses());
ASSERT_EQ(50, cache_simulator->miss_ratio_stats().miss_ratio());
auto handle = sim_cache->Lookup(access.block_key);
ASSERT_NE(nullptr, handle);
sim_cache->Release(handle);
}
TEST_F(CacheSimulatorTest, GhostPrioritizedCacheSimulator) {
const BlockCacheTraceRecord& access = GenerateGetRecord(kGetId);
std::unique_ptr<GhostCache> ghost_cache(new GhostCache(
NewLRUCache(/*capacity=*/kGhostCacheSize, /*num_shard_bits=*/1,
/*strict_capacity_limit=*/false,
/*high_pri_pool_ratio=*/0)));
std::unique_ptr<PrioritizedCacheSimulator> cache_simulator(
new PrioritizedCacheSimulator(
std::move(ghost_cache),
NewLRUCache(/*capacity=*/kCacheSize, /*num_shard_bits=*/1,
/*strict_capacity_limit=*/false,
/*high_pri_pool_ratio=*/0)));
cache_simulator->Access(access);
cache_simulator->Access(access);
ASSERT_EQ(2, cache_simulator->miss_ratio_stats().total_accesses());
// Both of them will be miss since we have a ghost cache.
ASSERT_EQ(100, cache_simulator->miss_ratio_stats().miss_ratio());
}
TEST_F(CacheSimulatorTest, HybridRowBlockCacheSimulator) {
uint64_t block_id = 100;
BlockCacheTraceRecord first_get = GenerateGetRecord(kGetId);
first_get.get_from_user_specified_snapshot = Boolean::kTrue;
BlockCacheTraceRecord second_get = GenerateGetRecord(kGetId + 1);
second_get.referenced_data_size = 0;
second_get.referenced_key_exist_in_block = Boolean::kFalse;
second_get.get_from_user_specified_snapshot = Boolean::kTrue;
BlockCacheTraceRecord third_get = GenerateGetRecord(kGetId + 2);
third_get.referenced_data_size = 0;
third_get.referenced_key_exist_in_block = Boolean::kFalse;
third_get.referenced_key = kRefKeyPrefix + "third_get";
// We didn't find the referenced key in the third get.
third_get.referenced_key_exist_in_block = Boolean::kFalse;
third_get.referenced_data_size = 0;
std::shared_ptr<Cache> sim_cache =
NewLRUCache(/*capacity=*/kCacheSize, /*num_shard_bits=*/1,
/*strict_capacity_limit=*/false,
/*high_pri_pool_ratio=*/0);
std::unique_ptr<HybridRowBlockCacheSimulator> cache_simulator(
new HybridRowBlockCacheSimulator(
nullptr, sim_cache, /*insert_blocks_row_kvpair_misses=*/true));
// The first get request accesses 10 blocks. We should only report 10 accesses
// and 100% miss.
for (uint32_t i = 0; i < 10; i++) {
first_get.block_key = kBlockKeyPrefix + std::to_string(block_id);
cache_simulator->Access(first_get);
block_id++;
}
ASSERT_EQ(10, cache_simulator->miss_ratio_stats().total_accesses());
ASSERT_EQ(100, cache_simulator->miss_ratio_stats().miss_ratio());
ASSERT_EQ(10, cache_simulator->miss_ratio_stats().user_accesses());
ASSERT_EQ(100, cache_simulator->miss_ratio_stats().user_miss_ratio());
auto handle =
sim_cache->Lookup(std::to_string(first_get.sst_fd_number) + "_" +
ExtractUserKey(first_get.referenced_key).ToString());
ASSERT_NE(nullptr, handle);
sim_cache->Release(handle);
for (uint32_t i = 100; i < block_id; i++) {
handle = sim_cache->Lookup(kBlockKeyPrefix + std::to_string(i));
ASSERT_NE(nullptr, handle);
sim_cache->Release(handle);
}
// The second get request accesses the same key. We should report 15
// access and 66% miss, 10 misses with 15 accesses.
// We do not consider these 5 block lookups as misses since the row hits the
// cache.
for (uint32_t i = 0; i < 5; i++) {
second_get.block_key = kBlockKeyPrefix + std::to_string(block_id);
cache_simulator->Access(second_get);
block_id++;
}
ASSERT_EQ(15, cache_simulator->miss_ratio_stats().total_accesses());
ASSERT_EQ(66, static_cast<uint64_t>(
cache_simulator->miss_ratio_stats().miss_ratio()));
ASSERT_EQ(15, cache_simulator->miss_ratio_stats().user_accesses());
ASSERT_EQ(66, static_cast<uint64_t>(
cache_simulator->miss_ratio_stats().user_miss_ratio()));
handle =
sim_cache->Lookup(std::to_string(second_get.sst_fd_number) + "_" +
ExtractUserKey(second_get.referenced_key).ToString());
ASSERT_NE(nullptr, handle);
sim_cache->Release(handle);
for (uint32_t i = 100; i < block_id; i++) {
handle = sim_cache->Lookup(kBlockKeyPrefix + std::to_string(i));
if (i < 110) {
ASSERT_NE(nullptr, handle) << i;
sim_cache->Release(handle);
} else {
ASSERT_EQ(nullptr, handle) << i;
}
}
// The third get on a different key and does not have a size.
// This key should not be inserted into the cache.
for (uint32_t i = 0; i < 5; i++) {
third_get.block_key = kBlockKeyPrefix + std::to_string(block_id);
cache_simulator->Access(third_get);
block_id++;
}
ASSERT_EQ(20, cache_simulator->miss_ratio_stats().total_accesses());
ASSERT_EQ(75, static_cast<uint64_t>(
cache_simulator->miss_ratio_stats().miss_ratio()));
ASSERT_EQ(20, cache_simulator->miss_ratio_stats().user_accesses());
ASSERT_EQ(75, static_cast<uint64_t>(
cache_simulator->miss_ratio_stats().user_miss_ratio()));
// Assert that the third key is not inserted into the cache.
handle = sim_cache->Lookup(std::to_string(third_get.sst_fd_number) + "_" +
third_get.referenced_key);
ASSERT_EQ(nullptr, handle);
for (uint32_t i = 100; i < block_id; i++) {
if (i < 110 || i >= 115) {
handle = sim_cache->Lookup(kBlockKeyPrefix + std::to_string(i));
ASSERT_NE(nullptr, handle) << i;
sim_cache->Release(handle);
} else {
handle = sim_cache->Lookup(kBlockKeyPrefix + std::to_string(i));
ASSERT_EQ(nullptr, handle) << i;
}
}
}
TEST_F(CacheSimulatorTest, HybridRowBlockCacheSimulatorGetTest) {
BlockCacheTraceRecord get = GenerateGetRecord(kGetId);
get.block_size = 1;
get.referenced_data_size = 0;
get.access_timestamp = 0;
get.block_key = "1";
get.get_id = 1;
get.get_from_user_specified_snapshot = Boolean::kFalse;
get.referenced_key =
kRefKeyPrefix + std::to_string(1) + kRefKeySequenceNumber;
get.no_insert = Boolean::kFalse;
get.sst_fd_number = 0;
get.get_from_user_specified_snapshot = Boolean::kFalse;
LRUCacheOptions co;
co.capacity = 16;
co.num_shard_bits = 1;
co.strict_capacity_limit = false;
co.high_pri_pool_ratio = 0;
co.metadata_charge_policy = kDontChargeCacheMetadata;
std::shared_ptr<Cache> sim_cache = NewLRUCache(co);
std::unique_ptr<HybridRowBlockCacheSimulator> cache_simulator(
new HybridRowBlockCacheSimulator(
nullptr, sim_cache, /*insert_blocks_row_kvpair_misses=*/true));
// Expect a miss and does not insert the row key-value pair since it does not
// have size.
cache_simulator->Access(get);
AssertCache(sim_cache, cache_simulator->miss_ratio_stats(), 1, 1, 1, {"1"},
{});
get.access_timestamp += 1;
get.referenced_data_size = 1;
get.block_key = "2";
cache_simulator->Access(get);
AssertCache(sim_cache, cache_simulator->miss_ratio_stats(), 3, 2, 2,
{"1", "2"}, {"1"});
get.access_timestamp += 1;
get.block_key = "3";
// K1 should not inserted again.
cache_simulator->Access(get);
AssertCache(sim_cache, cache_simulator->miss_ratio_stats(), 4, 3, 3,
{"1", "2", "3"}, {"1"});
// A second get request referencing the same key.
get.access_timestamp += 1;
get.get_id = 2;
get.block_key = "4";
get.referenced_data_size = 0;
cache_simulator->Access(get);
AssertCache(sim_cache, cache_simulator->miss_ratio_stats(), 4, 4, 3,
{"1", "2", "3"}, {"1"});
// A third get request searches three files, three different keys.
// And the second key observes a hit.
get.access_timestamp += 1;
get.referenced_data_size = 1;
get.get_id = 3;
get.block_key = "3";
get.referenced_key = kRefKeyPrefix + "2" + kRefKeySequenceNumber;
// K2 should observe a miss. Block 3 observes a hit.
cache_simulator->Access(get);
AssertCache(sim_cache, cache_simulator->miss_ratio_stats(), 5, 5, 3,
{"1", "2", "3"}, {"1", "2"});
get.access_timestamp += 1;
get.referenced_data_size = 1;
get.get_id = 3;
get.block_key = "4";
get.referenced_data_size = 1;
get.referenced_key = kRefKeyPrefix + "1" + kRefKeySequenceNumber;
// K1 should observe a hit.
cache_simulator->Access(get);
AssertCache(sim_cache, cache_simulator->miss_ratio_stats(), 5, 6, 3,
{"1", "2", "3"}, {"1", "2"});
get.access_timestamp += 1;
get.referenced_data_size = 1;
get.get_id = 3;
get.block_key = "4";
get.referenced_data_size = 1;
get.referenced_key = kRefKeyPrefix + "3" + kRefKeySequenceNumber;
// K3 should observe a miss.
// However, as the get already complete, we should not access k3 any more.
cache_simulator->Access(get);
AssertCache(sim_cache, cache_simulator->miss_ratio_stats(), 5, 7, 3,
{"1", "2", "3"}, {"1", "2"});
// A fourth get request searches one file and two blocks. One row key.
get.access_timestamp += 1;
get.get_id = 4;
get.block_key = "5";
get.referenced_key = kRefKeyPrefix + "4" + kRefKeySequenceNumber;
get.referenced_data_size = 1;
cache_simulator->Access(get);
AssertCache(sim_cache, cache_simulator->miss_ratio_stats(), 7, 8, 4,
{"1", "2", "3", "5"}, {"1", "2", "4"});
for (auto const& key : {"1", "2", "4"}) {
auto handle = sim_cache->Lookup("0_" + kRefKeyPrefix + key);
ASSERT_NE(nullptr, handle);
sim_cache->Release(handle);
}
// A bunch of insertions which evict cached row keys.
for (uint32_t i = 6; i < 100; i++) {
get.access_timestamp += 1;
get.get_id = 0;
get.block_key = std::to_string(i);
cache_simulator->Access(get);
}
get.get_id = 4;
// A different block.
get.block_key = "100";
// Same row key and should not be inserted again.
get.referenced_key = kRefKeyPrefix + "4" + kRefKeySequenceNumber;
get.referenced_data_size = 1;
cache_simulator->Access(get);
AssertCache(sim_cache, cache_simulator->miss_ratio_stats(), 16, 103, 99, {},
{});
for (auto const& key : {"1", "2", "4"}) {
auto handle = sim_cache->Lookup("0_" + kRefKeyPrefix + key);
ASSERT_EQ(nullptr, handle);
}
}
TEST_F(CacheSimulatorTest, HybridRowBlockNoInsertCacheSimulator) {
uint64_t block_id = 100;
BlockCacheTraceRecord first_get = GenerateGetRecord(kGetId);
std::shared_ptr<Cache> sim_cache =
NewLRUCache(/*capacity=*/kCacheSize, /*num_shard_bits=*/1,
/*strict_capacity_limit=*/false,
/*high_pri_pool_ratio=*/0);
std::unique_ptr<HybridRowBlockCacheSimulator> cache_simulator(
new HybridRowBlockCacheSimulator(
nullptr, sim_cache, /*insert_blocks_row_kvpair_misses=*/false));
for (uint32_t i = 0; i < 9; i++) {
first_get.block_key = kBlockKeyPrefix + std::to_string(block_id);
cache_simulator->Access(first_get);
block_id++;
}
auto handle =
sim_cache->Lookup(std::to_string(first_get.sst_fd_number) + "_" +
ExtractUserKey(first_get.referenced_key).ToString());
ASSERT_NE(nullptr, handle);
sim_cache->Release(handle);
// All blocks are missing from the cache since insert_blocks_row_kvpair_misses
// is set to false.
for (uint32_t i = 100; i < block_id; i++) {
handle = sim_cache->Lookup(kBlockKeyPrefix + std::to_string(i));
ASSERT_EQ(nullptr, handle);
}
}
TEST_F(CacheSimulatorTest, GhostHybridRowBlockCacheSimulator) {
std::unique_ptr<GhostCache> ghost_cache(new GhostCache(
NewLRUCache(/*capacity=*/kGhostCacheSize, /*num_shard_bits=*/1,
/*strict_capacity_limit=*/false,
/*high_pri_pool_ratio=*/0)));
const BlockCacheTraceRecord& first_get = GenerateGetRecord(kGetId);
const BlockCacheTraceRecord& second_get = GenerateGetRecord(kGetId + 1);
const BlockCacheTraceRecord& third_get = GenerateGetRecord(kGetId + 2);
std::unique_ptr<HybridRowBlockCacheSimulator> cache_simulator(
new HybridRowBlockCacheSimulator(
std::move(ghost_cache),
NewLRUCache(/*capacity=*/kCacheSize, /*num_shard_bits=*/1,
/*strict_capacity_limit=*/false,
/*high_pri_pool_ratio=*/0),
/*insert_blocks_row_kvpair_misses=*/false));
// Two get requests access the same key.
cache_simulator->Access(first_get);
cache_simulator->Access(second_get);
ASSERT_EQ(2, cache_simulator->miss_ratio_stats().total_accesses());
ASSERT_EQ(100, cache_simulator->miss_ratio_stats().miss_ratio());
ASSERT_EQ(2, cache_simulator->miss_ratio_stats().user_accesses());
ASSERT_EQ(100, cache_simulator->miss_ratio_stats().user_miss_ratio());
// We insert the key-value pair upon the second get request. A third get
// request should observe a hit.
for (uint32_t i = 0; i < 10; i++) {
cache_simulator->Access(third_get);
}
ASSERT_EQ(12, cache_simulator->miss_ratio_stats().total_accesses());
ASSERT_EQ(16, static_cast<uint64_t>(
cache_simulator->miss_ratio_stats().miss_ratio()));
ASSERT_EQ(12, cache_simulator->miss_ratio_stats().user_accesses());
ASSERT_EQ(16, static_cast<uint64_t>(
cache_simulator->miss_ratio_stats().user_miss_ratio()));
}
} // namespace rocksdb
int main(int argc, char** argv) {
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}
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