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Towards a production-quality ClockCache (#10418)

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Summary:
In this PR we bring ClockCache closer to production quality. We implement the following changes:
1. Fixed a few bugs in ClockCache.
2. ClockCache now fully supports ``strict_capacity_limit == false``: When an insertion over capacity is commanded, we allocate a handle separately from the hash table.
3. ClockCache now runs on almost every test in cache_test. The only exceptions are a test where either the LRU policy is required, and a test that dynamically increases the table capacity.
4. ClockCache now supports dynamically decreasing capacity via SetCapacity. (This is easy: we shrink the capacity upper bound and run the clock algorithm.)
5. Old FastLRUCache tests in lru_cache_test.cc are now also used on ClockCache.

As a byproduct of 1. and 2. we are able to turn on ClockCache in the stress tests.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10418

Test Plan:
- ``make -j24 USE_CLANG=1 COMPILE_WITH_ASAN=1 COMPILE_WITH_UBSAN=1 check``
- ``make -j24 USE_CLANG=1 COMPILE_WITH_TSAN=1 check``
- ``make -j24 USE_CLANG=1 COMPILE_WITH_ASAN=1 COMPILE_WITH_UBSAN=1 CRASH_TEST_EXT_ARGS="--duration=960 --cache_type=clock_cache" blackbox_crash_test_with_atomic_flush``
- ``make -j24 USE_CLANG=1 COMPILE_WITH_TSAN=1 CRASH_TEST_EXT_ARGS="--duration=960 --cache_type=clock_cache" blackbox_crash_test_with_atomic_flush``

Reviewed By: pdillinger

Differential Revision: D38170673

Pulled By: guidotag

fbshipit-source-id: 508987b9dc9d9d68f1a03eefac769820b680340a
main
Guido Tagliavini Ponce 2 years ago committed by Facebook GitHub Bot
parent 8db8b98f98
commit 9d7de6517c
6 changed files with 350 additions and 193 deletions
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  1. 151
      cache/cache_test.cc
  2. 112
      cache/clock_cache.cc
  3. 76
      cache/clock_cache.h
  4. 4
      cache/fast_lru_cache.cc
  5. 196
      cache/lru_cache_test.cc
  6. 4
      tools/db_crashtest.py

151
cache/cache_test.cc vendored
Unescape View File

@ -23,6 +23,11 @@
#include "util/coding.h" #include "util/coding.h"
#include "util/string_util.h" #include "util/string_util.h"
// FastLRUCache and ClockCache only support 16-byte keys, so some of
// the tests originally wrote for LRUCache do not work on the other caches.
// Those tests were adapted to use 16-byte keys. We kept the original ones.
// TODO: Remove the original tests if they ever become unused.
namespace ROCKSDB_NAMESPACE { namespace ROCKSDB_NAMESPACE {
namespace { namespace {
@ -58,17 +63,22 @@ int DecodeValue(void* v) {
return static_cast<int>(reinterpret_cast<uintptr_t>(v)); return static_cast<int>(reinterpret_cast<uintptr_t>(v));
} }
const std::string kLRU = "lru"; void DumbDeleter(const Slice& /*key*/, void* /*value*/) {}
const std::string kClock = "clock";
const std::string kFast = "fast";
void dumbDeleter(const Slice& /*key*/, void* /*value*/) {}
void eraseDeleter(const Slice& /*key*/, void* value) { void EraseDeleter1(const Slice& /*key*/, void* value) {
Cache* cache = reinterpret_cast<Cache*>(value); Cache* cache = reinterpret_cast<Cache*>(value);
cache->Erase("foo"); cache->Erase("foo");
} }
void EraseDeleter2(const Slice& /*key*/, void* value) {
Cache* cache = reinterpret_cast<Cache*>(value);
cache->Erase(EncodeKey16Bytes(1234));
}
const std::string kLRU = "lru";
const std::string kClock = "clock";
const std::string kFast = "fast";
} // anonymous namespace } // anonymous namespace
class CacheTest : public testing::TestWithParam<std::string> { class CacheTest : public testing::TestWithParam<std::string> {
@ -223,13 +233,9 @@ class LRUCacheTest : public CacheTest {};
TEST_P(CacheTest, UsageTest) { TEST_P(CacheTest, UsageTest) {
auto type = GetParam(); auto type = GetParam();
if (type == kFast || type == kClock) {
ROCKSDB_GTEST_BYPASS("FastLRUCache and ClockCache require 16-byte keys.");
return;
}
// cache is std::shared_ptr and will be automatically cleaned up. // cache is std::shared_ptr and will be automatically cleaned up.
const uint64_t kCapacity = 100000; const size_t kCapacity = 100000;
auto cache = NewCache(kCapacity, 8, false, kDontChargeCacheMetadata); auto cache = NewCache(kCapacity, 8, false, kDontChargeCacheMetadata);
auto precise_cache = NewCache(kCapacity, 0, false, kFullChargeCacheMetadata); auto precise_cache = NewCache(kCapacity, 0, false, kFullChargeCacheMetadata);
ASSERT_EQ(0, cache->GetUsage()); ASSERT_EQ(0, cache->GetUsage());
@ -239,12 +245,17 @@ TEST_P(CacheTest, UsageTest) {
char value[10] = "abcdef"; char value[10] = "abcdef";
// make sure everything will be cached // make sure everything will be cached
for (int i = 1; i < 100; ++i) { for (int i = 1; i < 100; ++i) {
std::string key(i, 'a'); std::string key;
if (type == kLRU) {
key = std::string(i, 'a');
} else {
key = EncodeKey(i);
}
auto kv_size = key.size() + 5; auto kv_size = key.size() + 5;
ASSERT_OK(cache->Insert(key, reinterpret_cast<void*>(value), kv_size, ASSERT_OK(cache->Insert(key, reinterpret_cast<void*>(value), kv_size,
dumbDeleter)); DumbDeleter));
ASSERT_OK(precise_cache->Insert(key, reinterpret_cast<void*>(value), ASSERT_OK(precise_cache->Insert(key, reinterpret_cast<void*>(value),
kv_size, dumbDeleter)); kv_size, DumbDeleter));
usage += kv_size; usage += kv_size;
ASSERT_EQ(usage, cache->GetUsage()); ASSERT_EQ(usage, cache->GetUsage());
ASSERT_LT(usage, precise_cache->GetUsage()); ASSERT_LT(usage, precise_cache->GetUsage());
@ -256,12 +267,17 @@ TEST_P(CacheTest, UsageTest) {
ASSERT_EQ(0, precise_cache->GetUsage()); ASSERT_EQ(0, precise_cache->GetUsage());
// make sure the cache will be overloaded // make sure the cache will be overloaded
for (uint64_t i = 1; i < kCapacity; ++i) { for (size_t i = 1; i < kCapacity; ++i) {
auto key = std::to_string(i); std::string key;
if (type == kLRU) {
key = std::to_string(i);
} else {
key = EncodeKey(static_cast<int>(1000 + i));
}
ASSERT_OK(cache->Insert(key, reinterpret_cast<void*>(value), key.size() + 5, ASSERT_OK(cache->Insert(key, reinterpret_cast<void*>(value), key.size() + 5,
dumbDeleter)); DumbDeleter));
ASSERT_OK(precise_cache->Insert(key, reinterpret_cast<void*>(value), ASSERT_OK(precise_cache->Insert(key, reinterpret_cast<void*>(value),
key.size() + 5, dumbDeleter)); key.size() + 5, DumbDeleter));
} }
// the usage should be close to the capacity // the usage should be close to the capacity
@ -271,15 +287,18 @@ TEST_P(CacheTest, UsageTest) {
ASSERT_LT(kCapacity * 0.95, precise_cache->GetUsage()); ASSERT_LT(kCapacity * 0.95, precise_cache->GetUsage());
} }
// TODO: This test takes longer than expected on ClockCache. This is
// because the values size estimate at construction is too sloppy.
// Fix this.
// Why is it so slow? The cache is constructed with an estimate of 1, but
// then the charge is claimed to be 21. This will cause the hash table
// to be extremely sparse, which in turn means clock needs to scan too
// many slots to find victims.
TEST_P(CacheTest, PinnedUsageTest) { TEST_P(CacheTest, PinnedUsageTest) {
auto type = GetParam(); auto type = GetParam();
if (type == kFast || type == kClock) {
ROCKSDB_GTEST_BYPASS("FastLRUCache and ClockCache require 16-byte keys.");
return;
}
// cache is std::shared_ptr and will be automatically cleaned up. // cache is std::shared_ptr and will be automatically cleaned up.
const uint64_t kCapacity = 200000; const size_t kCapacity = 200000;
auto cache = NewCache(kCapacity, 8, false, kDontChargeCacheMetadata); auto cache = NewCache(kCapacity, 8, false, kDontChargeCacheMetadata);
auto precise_cache = NewCache(kCapacity, 8, false, kFullChargeCacheMetadata); auto precise_cache = NewCache(kCapacity, 8, false, kFullChargeCacheMetadata);
@ -292,15 +311,20 @@ TEST_P(CacheTest, PinnedUsageTest) {
// Add entries. Unpin some of them after insertion. Then, pin some of them // Add entries. Unpin some of them after insertion. Then, pin some of them
// again. Check GetPinnedUsage(). // again. Check GetPinnedUsage().
for (int i = 1; i < 100; ++i) { for (int i = 1; i < 100; ++i) {
std::string key(i, 'a'); std::string key;
if (type == kLRU) {
key = std::string(i, 'a');
} else {
key = EncodeKey(i);
}
auto kv_size = key.size() + 5; auto kv_size = key.size() + 5;
Cache::Handle* handle; Cache::Handle* handle;
Cache::Handle* handle_in_precise_cache; Cache::Handle* handle_in_precise_cache;
ASSERT_OK(cache->Insert(key, reinterpret_cast<void*>(value), kv_size, ASSERT_OK(cache->Insert(key, reinterpret_cast<void*>(value), kv_size,
dumbDeleter, &handle)); DumbDeleter, &handle));
assert(handle); assert(handle);
ASSERT_OK(precise_cache->Insert(key, reinterpret_cast<void*>(value), ASSERT_OK(precise_cache->Insert(key, reinterpret_cast<void*>(value),
kv_size, dumbDeleter, kv_size, DumbDeleter,
&handle_in_precise_cache)); &handle_in_precise_cache));
assert(handle_in_precise_cache); assert(handle_in_precise_cache);
pinned_usage += kv_size; pinned_usage += kv_size;
@ -334,12 +358,17 @@ TEST_P(CacheTest, PinnedUsageTest) {
ASSERT_LT(pinned_usage, precise_cache_pinned_usage); ASSERT_LT(pinned_usage, precise_cache_pinned_usage);
// check that overloading the cache does not change the pinned usage // check that overloading the cache does not change the pinned usage
for (uint64_t i = 1; i < 2 * kCapacity; ++i) { for (size_t i = 1; i < 2 * kCapacity; ++i) {
auto key = std::to_string(i); std::string key;
if (type == kLRU) {
key = std::to_string(i);
} else {
key = EncodeKey(static_cast<int>(1000 + i));
}
ASSERT_OK(cache->Insert(key, reinterpret_cast<void*>(value), key.size() + 5, ASSERT_OK(cache->Insert(key, reinterpret_cast<void*>(value), key.size() + 5,
dumbDeleter)); DumbDeleter));
ASSERT_OK(precise_cache->Insert(key, reinterpret_cast<void*>(value), ASSERT_OK(precise_cache->Insert(key, reinterpret_cast<void*>(value),
key.size() + 5, dumbDeleter)); key.size() + 5, DumbDeleter));
} }
ASSERT_EQ(pinned_usage, cache->GetPinnedUsage()); ASSERT_EQ(pinned_usage, cache->GetPinnedUsage());
ASSERT_EQ(precise_cache_pinned_usage, precise_cache->GetPinnedUsage()); ASSERT_EQ(precise_cache_pinned_usage, precise_cache->GetPinnedUsage());
@ -447,7 +476,7 @@ TEST_P(CacheTest, EvictionPolicy) {
Insert(200, 201); Insert(200, 201);
// Frequently used entry must be kept around // Frequently used entry must be kept around
for (int i = 0; i < kCacheSize * 2; i++) { for (int i = 0; i < 2 * kCacheSize; i++) {
Insert(1000+i, 2000+i); Insert(1000+i, 2000+i);
ASSERT_EQ(101, Lookup(100)); ASSERT_EQ(101, Lookup(100));
} }
@ -500,9 +529,7 @@ TEST_P(CacheTest, EvictionPolicyRef) {
Insert(303, 104); Insert(303, 104);
// Insert entries much more than cache capacity. // Insert entries much more than cache capacity.
double load_factor = for (int i = 0; i < 100 * kCacheSize; i++) {
std::min(fast_lru_cache::kLoadFactor, clock_cache::kLoadFactor);
for (int i = 0; i < 2 * static_cast<int>(kCacheSize / load_factor); i++) {
Insert(1000 + i, 2000 + i); Insert(1000 + i, 2000 + i);
} }
@ -533,31 +560,40 @@ TEST_P(CacheTest, EvictionPolicyRef) {
TEST_P(CacheTest, EvictEmptyCache) { TEST_P(CacheTest, EvictEmptyCache) {
auto type = GetParam(); auto type = GetParam();
if (type == kFast || type == kClock) {
ROCKSDB_GTEST_BYPASS("FastLRUCache and ClockCache require 16-byte keys.");
return;
}
// Insert item large than capacity to trigger eviction on empty cache. // Insert item large than capacity to trigger eviction on empty cache.
auto cache = NewCache(1, 0, false); auto cache = NewCache(1, 0, false);
ASSERT_OK(cache->Insert("foo", nullptr, 10, dumbDeleter)); if (type == kLRU) {
ASSERT_OK(cache->Insert("foo", nullptr, 10, DumbDeleter));
} else {
ASSERT_OK(cache->Insert(EncodeKey(1000), nullptr, 10, DumbDeleter));
}
} }
TEST_P(CacheTest, EraseFromDeleter) { TEST_P(CacheTest, EraseFromDeleter) {
auto type = GetParam(); auto type = GetParam();
if (type == kFast || type == kClock) {
ROCKSDB_GTEST_BYPASS("FastLRUCache and ClockCache require 16-byte keys.");
return;
}
// Have deleter which will erase item from cache, which will re-enter // Have deleter which will erase item from cache, which will re-enter
// the cache at that point. // the cache at that point.
std::shared_ptr<Cache> cache = NewCache(10, 0, false); std::shared_ptr<Cache> cache = NewCache(10, 0, false);
ASSERT_OK(cache->Insert("foo", nullptr, 1, dumbDeleter)); std::string foo, bar;
ASSERT_OK(cache->Insert("bar", cache.get(), 1, eraseDeleter)); Cache::DeleterFn erase_deleter;
cache->Erase("bar"); if (type == kLRU) {
ASSERT_EQ(nullptr, cache->Lookup("foo")); foo = "foo";
ASSERT_EQ(nullptr, cache->Lookup("bar")); bar = "bar";
erase_deleter = EraseDeleter1;
} else {
foo = EncodeKey(1234);
bar = EncodeKey(5678);
erase_deleter = EraseDeleter2;
}
ASSERT_OK(cache->Insert(foo, nullptr, 1, DumbDeleter));
ASSERT_OK(cache->Insert(bar, cache.get(), 1, erase_deleter));
cache->Erase(bar);
ASSERT_EQ(nullptr, cache->Lookup(foo));
ASSERT_EQ(nullptr, cache->Lookup(bar));
} }
TEST_P(CacheTest, ErasedHandleState) { TEST_P(CacheTest, ErasedHandleState) {
@ -590,9 +626,9 @@ TEST_P(CacheTest, HeavyEntries) {
const int kHeavy = 10; const int kHeavy = 10;
int added = 0; int added = 0;
int index = 0; int index = 0;
while (added < 2*kCacheSize) { while (added < 2 * kCacheSize) {
const int weight = (index & 1) ? kLight : kHeavy; const int weight = (index & 1) ? kLight : kHeavy;
Insert(index, 1000+index, weight); Insert(index, 1000 + index, weight);
added += weight; added += weight;
index++; index++;
} }
@ -603,7 +639,7 @@ TEST_P(CacheTest, HeavyEntries) {
int r = Lookup(i); int r = Lookup(i);
if (r >= 0) { if (r >= 0) {
cached_weight += weight; cached_weight += weight;
ASSERT_EQ(1000+i, r); ASSERT_EQ(1000 + i, r);
} }
} }
ASSERT_LE(cached_weight, kCacheSize + kCacheSize/10); ASSERT_LE(cached_weight, kCacheSize + kCacheSize/10);
@ -615,7 +651,6 @@ TEST_P(CacheTest, NewId) {
ASSERT_NE(a, b); ASSERT_NE(a, b);
} }
class Value { class Value {
public: public:
explicit Value(int v) : v_(v) {} explicit Value(int v) : v_(v) {}
@ -664,7 +699,8 @@ TEST_P(CacheTest, SetCapacity) {
auto type = GetParam(); auto type = GetParam();
if (type == kFast || type == kClock) { if (type == kFast || type == kClock) {
ROCKSDB_GTEST_BYPASS( ROCKSDB_GTEST_BYPASS(
"FastLRUCache and ClockCache don't support capacity adjustments."); "FastLRUCache and ClockCache don't support arbitrary capacity "
"adjustments.");
return; return;
} }
// test1: increase capacity // test1: increase capacity
@ -716,9 +752,9 @@ TEST_P(CacheTest, SetCapacity) {
TEST_P(LRUCacheTest, SetStrictCapacityLimit) { TEST_P(LRUCacheTest, SetStrictCapacityLimit) {
auto type = GetParam(); auto type = GetParam();
if (type == kFast || type == kClock) { if (type == kFast) {
ROCKSDB_GTEST_BYPASS( ROCKSDB_GTEST_BYPASS(
"FastLRUCache and ClockCache don't support an unbounded number of " "FastLRUCache only supports a limited number of "
"inserts beyond " "inserts beyond "
"capacity."); "capacity.");
return; return;
@ -775,9 +811,8 @@ TEST_P(LRUCacheTest, SetStrictCapacityLimit) {
TEST_P(CacheTest, OverCapacity) { TEST_P(CacheTest, OverCapacity) {
auto type = GetParam(); auto type = GetParam();
if (type == kFast || type == kClock) { if (type == kClock) {
ROCKSDB_GTEST_BYPASS( ROCKSDB_GTEST_BYPASS("Requires LRU eviction policy.");
"FastLRUCache and ClockCache don't support capacity adjustments.");
return; return;
} }
size_t n = 10; size_t n = 10;

112
cache/clock_cache.cc vendored
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@ -69,10 +69,10 @@ ClockHandle* ClockHandleTable::Lookup(const Slice& key, uint32_t hash) {
// updates where it would be possible to combine into one CAS (more metadata // updates where it would be possible to combine into one CAS (more metadata
// under one atomic field) or maybe two atomic updates (one arithmetic, one // under one atomic field) or maybe two atomic updates (one arithmetic, one
// bitwise). Something to think about optimizing. // bitwise). Something to think about optimizing.
e->InternalToExternalRef();
e->SetHit(); e->SetHit();
// The handle is now referenced, so we take it out of clock. // The handle is now referenced, so we take it out of clock.
ClockOff(e); ClockOff(e);
e->InternalToExternalRef();
} }
return e; return e;
@ -312,17 +312,20 @@ void ClockHandleTable::ClockRun(size_t charge) {
// hot element, it will be hard to get an exclusive ref. // hot element, it will be hard to get an exclusive ref.
// Do we need a mechanism to prevent an element from sitting // Do we need a mechanism to prevent an element from sitting
// for a long time in cache waiting to be evicted? // for a long time in cache waiting to be evicted?
assert(charge <= capacity_);
autovector<ClockHandle> deleted; autovector<ClockHandle> deleted;
uint32_t max_iterations = uint32_t max_iterations =
1 + static_cast<uint32_t>(GetTableSize() * kLoadFactor); ClockHandle::ClockPriority::HIGH *
(1 +
static_cast<uint32_t>(
GetTableSize() *
kLoadFactor)); // It may take up to HIGH passes to evict an element.
size_t usage_local = usage_; size_t usage_local = usage_;
while (usage_local + charge > capacity_ && max_iterations--) { size_t capacity_local = capacity_;
while (usage_local + charge > capacity_local && max_iterations--) {
uint32_t steps = 1 + static_cast<uint32_t>(1 / kLoadFactor); uint32_t steps = 1 + static_cast<uint32_t>(1 / kLoadFactor);
uint32_t clock_pointer_local = (clock_pointer_ += steps) - steps; uint32_t clock_pointer_local = (clock_pointer_ += steps) - steps;
for (uint32_t i = 0; i < steps; i++) { for (uint32_t i = 0; i < steps; i++) {
ClockHandle* h = &array_[ModTableSize(clock_pointer_local + i)]; ClockHandle* h = &array_[ModTableSize(clock_pointer_local + i)];
if (h->TryExclusiveRef()) { if (h->TryExclusiveRef()) {
if (h->WillBeDeleted()) { if (h->WillBeDeleted()) {
Remove(h, &deleted); Remove(h, &deleted);
@ -335,7 +338,6 @@ void ClockHandleTable::ClockRun(size_t charge) {
// exclusive ref, we know we are in the latter case. This can only // exclusive ref, we know we are in the latter case. This can only
// happen when the last external reference to an element was // happen when the last external reference to an element was
// released, and the element was not immediately removed. // released, and the element was not immediately removed.
ClockOn(h); ClockOn(h);
} }
ClockHandle::ClockPriority priority = h->GetClockPriority(); ClockHandle::ClockPriority priority = h->GetClockPriority();
@ -358,6 +360,7 @@ ClockCacheShard::ClockCacheShard(
size_t capacity, size_t estimated_value_size, bool strict_capacity_limit, size_t capacity, size_t estimated_value_size, bool strict_capacity_limit,
CacheMetadataChargePolicy metadata_charge_policy) CacheMetadataChargePolicy metadata_charge_policy)
: strict_capacity_limit_(strict_capacity_limit), : strict_capacity_limit_(strict_capacity_limit),
detached_usage_(0),
table_(capacity, CalcHashBits(capacity, estimated_value_size, table_(capacity, CalcHashBits(capacity, estimated_value_size,
metadata_charge_policy)) { metadata_charge_policy)) {
set_metadata_charge_policy(metadata_charge_policy); set_metadata_charge_policy(metadata_charge_policy);
@ -430,12 +433,16 @@ int ClockCacheShard::CalcHashBits(
return FloorLog2((num_entries << 1) - 1); return FloorLog2((num_entries << 1) - 1);
} }
void ClockCacheShard::SetCapacity(size_t /*capacity*/) { void ClockCacheShard::SetCapacity(size_t capacity) {
assert(false); // Not supported. if (capacity > table_.GetCapacity()) {
assert(false); // Not supported.
}
table_.SetCapacity(capacity);
table_.ClockRun(detached_usage_);
} }
void ClockCacheShard::SetStrictCapacityLimit(bool /*strict_capacity_limit*/) { void ClockCacheShard::SetStrictCapacityLimit(bool strict_capacity_limit) {
assert(false); // Not supported. strict_capacity_limit_ = strict_capacity_limit;
} }
Status ClockCacheShard::Insert(const Slice& key, uint32_t hash, void* value, Status ClockCacheShard::Insert(const Slice& key, uint32_t hash, void* value,
@ -459,27 +466,32 @@ Status ClockCacheShard::Insert(const Slice& key, uint32_t hash, void* value,
Status s = Status::OK(); Status s = Status::OK();
// Use a local copy to minimize cache synchronization.
size_t detached_usage = detached_usage_;
// Free space with the clock policy until enough space is freed or there are // Free space with the clock policy until enough space is freed or there are
// no evictable elements. // no evictable elements.
table_.ClockRun(tmp.total_charge); table_.ClockRun(tmp.total_charge + detached_usage);
// occupancy_ and usage_ are contended members across concurrent updates // Use local copies to minimize cache synchronization
// on the same shard, so we use a single copy to reduce cache synchronization. // (occupancy_ and usage_ are read and written by all insertions).
uint32_t occupancy_local = table_.GetOccupancy(); uint32_t occupancy_local = table_.GetOccupancy();
size_t usage_local = table_.GetUsage(); size_t total_usage = table_.GetUsage() + detached_usage;
assert(occupancy_local <= table_.GetOccupancyLimit());
// TODO: Currently we support strict_capacity_limit == false as long as the
autovector<ClockHandle> deleted; // number of pinned elements is below table_.GetOccupancyLimit(). We can
// always support it as follows: whenever we exceed this limit, we dynamically
if ((usage_local + tmp.total_charge > table_.GetCapacity() && // allocate a handle and return it (when the user provides a handle pointer,
(strict_capacity_limit_ || handle == nullptr)) || // of course). Then, Release checks whether the handle was dynamically
occupancy_local > table_.GetOccupancyLimit()) { // allocated, or is stored in the table.
if (total_usage + tmp.total_charge > table_.GetCapacity() &&
(strict_capacity_limit_ || handle == nullptr)) {
if (handle == nullptr) { if (handle == nullptr) {
// Don't insert the entry but still return ok, as if the entry inserted // Don't insert the entry but still return ok, as if the entry inserted
// into cache and get evicted immediately. // into cache and get evicted immediately.
deleted.push_back(tmp); tmp.FreeData();
} else { } else {
if (occupancy_local > table_.GetOccupancyLimit()) { if (occupancy_local + 1 > table_.GetOccupancyLimit()) {
// TODO: Consider using a distinct status for this case, but usually // TODO: Consider using a distinct status for this case, but usually
// it will be handled the same way as reaching charge capacity limit // it will be handled the same way as reaching charge capacity limit
s = Status::MemoryLimit( s = Status::MemoryLimit(
@ -491,22 +503,33 @@ Status ClockCacheShard::Insert(const Slice& key, uint32_t hash, void* value,
} }
} }
} else { } else {
// Insert into the cache. Note that the cache might get larger than its ClockHandle* h;
// capacity if not enough space was freed up. if (occupancy_local + 1 > table_.GetOccupancyLimit()) {
ClockHandle* h = table_.Insert(&tmp, &deleted, handle != nullptr); // Even if the user wishes to overload the cache, we can't insert into
assert(h != nullptr); // The occupancy is way below the table size, so this // the hash table. Instead, we dynamically allocate a new handle.
// insertion should never fail. h = new ClockHandle();
*h = tmp;
h->SetDetached();
h->TryExternalRef();
detached_usage_ += h->total_charge;
// TODO: Return special status?
} else {
// Insert into the cache. Note that the cache might get larger than its
// capacity if not enough space was freed up.
autovector<ClockHandle> deleted;
h = table_.Insert(&tmp, &deleted, handle != nullptr);
assert(h != nullptr); // The occupancy is way below the table size, so
// this insertion should never fail.
if (deleted.size() > 0) {
s = Status::OkOverwritten();
}
table_.Free(&deleted);
}
if (handle != nullptr) { if (handle != nullptr) {
*handle = reinterpret_cast<Cache::Handle*>(h); *handle = reinterpret_cast<Cache::Handle*>(h);
} }
if (deleted.size() > 0) {
s = Status::OkOverwritten();
}
} }
table_.Free(&deleted);
return s; return s;
} }
@ -516,7 +539,7 @@ Cache::Handle* ClockCacheShard::Lookup(const Slice& key, uint32_t hash) {
bool ClockCacheShard::Ref(Cache::Handle* h) { bool ClockCacheShard::Ref(Cache::Handle* h) {
ClockHandle* e = reinterpret_cast<ClockHandle*>(h); ClockHandle* e = reinterpret_cast<ClockHandle*>(h);
assert(e->HasExternalRefs()); assert(e->ExternalRefs() > 0);
return e->TryExternalRef(); return e->TryExternalRef();
} }
@ -530,6 +553,20 @@ bool ClockCacheShard::Release(Cache::Handle* handle, bool erase_if_last_ref) {
} }
ClockHandle* h = reinterpret_cast<ClockHandle*>(handle); ClockHandle* h = reinterpret_cast<ClockHandle*>(handle);
if (UNLIKELY(h->IsDetached())) {
h->ReleaseExternalRef();
if (h->TryExclusiveRef()) {
// Only the last reference will succeed.
// Don't bother releasing the exclusive ref.
h->FreeData();
detached_usage_ -= h->total_charge;
delete h;
return true;
}
return false;
}
uint32_t refs = h->refs; uint32_t refs = h->refs;
bool last_reference = ((refs & ClockHandle::EXTERNAL_REFS) == 1); bool last_reference = ((refs & ClockHandle::EXTERNAL_REFS) == 1);
bool will_be_deleted = refs & ClockHandle::WILL_BE_DELETED; bool will_be_deleted = refs & ClockHandle::WILL_BE_DELETED;
@ -570,13 +607,14 @@ size_t ClockCacheShard::GetPinnedUsage() const {
table_.ConstApplyToEntriesRange( table_.ConstApplyToEntriesRange(
[&clock_usage](ClockHandle* h) { [&clock_usage](ClockHandle* h) {
if (h->HasExternalRefs()) { if (h->ExternalRefs() > 1) {
// We check > 1 because we are holding an external ref.
clock_usage += h->total_charge; clock_usage += h->total_charge;
} }
}, },
0, table_.GetTableSize(), true); 0, table_.GetTableSize(), true);
return clock_usage; return clock_usage + detached_usage_;
} }
ClockCache::ClockCache(size_t capacity, size_t estimated_value_size, ClockCache::ClockCache(size_t capacity, size_t estimated_value_size,

76
cache/clock_cache.h vendored
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@ -9,6 +9,8 @@
#pragma once #pragma once
#include <sys/types.h>
#include <array> #include <array>
#include <atomic> #include <atomic>
#include <cstdint> #include <cstdint>
@ -28,6 +30,9 @@ namespace ROCKSDB_NAMESPACE {
namespace clock_cache { namespace clock_cache {
// Forward declaration of friend class.
class ClockCacheTest;
// An experimental alternative to LRUCache, using a lock-free, open-addressed // An experimental alternative to LRUCache, using a lock-free, open-addressed
// hash table and clock eviction. // hash table and clock eviction.
@ -63,10 +68,10 @@ namespace clock_cache {
// can't be immediately deleted. In these cases, the flag will be later read // can't be immediately deleted. In these cases, the flag will be later read
// and acted upon by the eviction algorithm. Importantly, WILL_BE_DELETED is // and acted upon by the eviction algorithm. Importantly, WILL_BE_DELETED is
// used not only to defer deletions, but also as a barrier for external // used not only to defer deletions, but also as a barrier for external
// references: once WILL_BE_DELETED is set, lookups (which are the means to // references: once WILL_BE_DELETED is set, lookups (which are the most
// acquire new external references) will ignore the handle. For this reason, // common way to acquire new external references) will ignore the handle.
// when WILL_BE_DELETED is set, we say the handle is invisible (and // For this reason, when WILL_BE_DELETED is set, we say the handle is
// otherwise, that it's visible). // invisible (and, otherwise, that it's visible).
// //
// //
// 3. HASHING AND COLLISION RESOLUTION // 3. HASHING AND COLLISION RESOLUTION
@ -192,10 +197,10 @@ struct ClockHandle {
size_t total_charge; size_t total_charge;
std::array<char, kCacheKeySize> key_data; std::array<char, kCacheKeySize> key_data;
static constexpr uint8_t kIsElementOffset = 1; static constexpr uint8_t kIsElementOffset = 0;
static constexpr uint8_t kClockPriorityOffset = 2; static constexpr uint8_t kClockPriorityOffset = 1;
static constexpr uint8_t kIsHitOffset = 4; static constexpr uint8_t kIsHitOffset = 3;
static constexpr uint8_t kCachePriorityOffset = 5; static constexpr uint8_t kCachePriorityOffset = 4;
enum Flags : uint8_t { enum Flags : uint8_t {
// Whether the slot is in use by an element. // Whether the slot is in use by an element.
@ -252,9 +257,8 @@ struct ClockHandle {
// Whether a thread has an exclusive reference to the slot. // Whether a thread has an exclusive reference to the slot.
EXCLUSIVE_REF = uint32_t{1} << kExclusiveRefOffset, // Bit 30 EXCLUSIVE_REF = uint32_t{1} << kExclusiveRefOffset, // Bit 30
// Whether the handle will be deleted soon. When this bit is set, new // Whether the handle will be deleted soon. When this bit is set, new
// internal // internal references to this handle stop being accepted.
// or external references to this handle stop being accepted. // External references may still be granted---they can be created from
// There is an exception: external references can be created from
// existing external references, or converting from existing internal // existing external references, or converting from existing internal
// references. // references.
WILL_BE_DELETED = uint32_t{1} << kWillBeDeletedOffset // Bit 31 WILL_BE_DELETED = uint32_t{1} << kWillBeDeletedOffset // Bit 31
@ -274,6 +278,9 @@ struct ClockHandle {
std::atomic<uint32_t> refs; std::atomic<uint32_t> refs;
// True iff the handle is allocated separately from hash table.
bool detached;
ClockHandle() ClockHandle()
: value(nullptr), : value(nullptr),
deleter(nullptr), deleter(nullptr),
@ -281,7 +288,8 @@ struct ClockHandle {
total_charge(0), total_charge(0),
flags(0), flags(0),
displacements(0), displacements(0),
refs(0) { refs(0),
detached(false) {
SetWillBeDeleted(false); SetWillBeDeleted(false);
SetIsElement(false); SetIsElement(false);
SetClockPriority(ClockPriority::NONE); SetClockPriority(ClockPriority::NONE);
@ -300,6 +308,7 @@ struct ClockHandle {
value = other.value; value = other.value;
deleter = other.deleter; deleter = other.deleter;
key_data = other.key_data; key_data = other.key_data;
hash = other.hash;
total_charge = other.total_charge; total_charge = other.total_charge;
} }
@ -350,13 +359,13 @@ struct ClockHandle {
// flags functions. // flags functions.
bool IsElement() const { return flags & IS_ELEMENT; } bool IsElement() const { return flags & Flags::IS_ELEMENT; }
void SetIsElement(bool is_element) { void SetIsElement(bool is_element) {
if (is_element) { if (is_element) {
flags |= IS_ELEMENT; flags |= Flags::IS_ELEMENT;
} else { } else {
flags &= static_cast<uint8_t>(~IS_ELEMENT); flags &= static_cast<uint8_t>(~Flags::IS_ELEMENT);
} }
} }
@ -400,6 +409,10 @@ struct ClockHandle {
flags |= new_priority; flags |= new_priority;
} }
bool IsDetached() { return detached; }
void SetDetached() { detached = true; }
inline bool IsEmpty() const { inline bool IsEmpty() const {
return !this->IsElement() && this->displacements == 0; return !this->IsElement() && this->displacements == 0;
} }
@ -424,7 +437,9 @@ struct ClockHandle {
} }
} }
bool HasExternalRefs() const { return (refs & EXTERNAL_REFS) > 0; } uint32_t ExternalRefs() const {
return (refs & EXTERNAL_REFS) >> kExternalRefsOffset;
}
// Tries to take an internal ref. Returns true iff it succeeds. // Tries to take an internal ref. Returns true iff it succeeds.
inline bool TryInternalRef() { inline bool TryInternalRef() {
@ -437,7 +452,7 @@ struct ClockHandle {
// Tries to take an external ref. Returns true iff it succeeds. // Tries to take an external ref. Returns true iff it succeeds.
inline bool TryExternalRef() { inline bool TryExternalRef() {
if (!((refs += kOneExternalRef) & (EXCLUSIVE_REF | WILL_BE_DELETED))) { if (!((refs += kOneExternalRef) & EXCLUSIVE_REF)) {
return true; return true;
} }
refs -= kOneExternalRef; refs -= kOneExternalRef;
@ -529,8 +544,8 @@ class ClockHandleTable {
// Makes h non-evictable. // Makes h non-evictable.
void ClockOff(ClockHandle* h); void ClockOff(ClockHandle* h);
// Runs the clock eviction algorithm until there is enough space to // Runs the clock eviction algorithm until usage_ + charge is at most
// insert an element with the given charge. // capacity_.
void ClockRun(size_t charge); void ClockRun(size_t charge);
// Remove h from the hash table. Requires an exclusive ref to h. // Remove h from the hash table. Requires an exclusive ref to h.
@ -548,8 +563,6 @@ class ClockHandleTable {
RemoveAll(key, hash, probe, deleted); RemoveAll(key, hash, probe, deleted);
} }
void Free(autovector<ClockHandle>* deleted);
// Tries to remove h from the hash table. If the attempt is successful, // Tries to remove h from the hash table. If the attempt is successful,
// the function hands over an exclusive ref to h. // the function hands over an exclusive ref to h.
bool TryRemove(ClockHandle* h, autovector<ClockHandle>* deleted); bool TryRemove(ClockHandle* h, autovector<ClockHandle>* deleted);
@ -558,6 +571,11 @@ class ClockHandleTable {
// success. Requires that the caller thread has no shared ref to h. // success. Requires that the caller thread has no shared ref to h.
bool SpinTryRemove(ClockHandle* h, autovector<ClockHandle>* deleted); bool SpinTryRemove(ClockHandle* h, autovector<ClockHandle>* deleted);
// Call this function after an Insert, Remove, RemoveAll, TryRemove
// or SpinTryRemove. It frees the deleted values and updates the hash table
// metadata.
void Free(autovector<ClockHandle>* deleted);
template <typename T> template <typename T>
void ApplyToEntriesRange(T func, uint32_t index_begin, uint32_t index_end, void ApplyToEntriesRange(T func, uint32_t index_begin, uint32_t index_end,
bool apply_if_will_be_deleted) { bool apply_if_will_be_deleted) {
@ -579,12 +597,15 @@ class ClockHandleTable {
bool apply_if_will_be_deleted) const { bool apply_if_will_be_deleted) const {
for (uint32_t i = index_begin; i < index_end; i++) { for (uint32_t i = index_begin; i < index_end; i++) {
ClockHandle* h = &array_[i]; ClockHandle* h = &array_[i];
if (h->TryExclusiveRef()) { // We take an external ref because we are handing over control
// to a user-defined function, and because the handle will not be
// modified.
if (h->TryExternalRef()) {
if (h->IsElement() && if (h->IsElement() &&
(apply_if_will_be_deleted || !h->WillBeDeleted())) { (apply_if_will_be_deleted || !h->WillBeDeleted())) {
func(h); func(h);
} }
h->ReleaseExclusiveRef(); h->ReleaseExternalRef();
} }
} }
} }
@ -601,6 +622,8 @@ class ClockHandleTable {
size_t GetCapacity() const { return capacity_; } size_t GetCapacity() const { return capacity_; }
void SetCapacity(size_t capacity) { capacity_ = capacity; }
// Returns x mod 2^{length_bits_}. // Returns x mod 2^{length_bits_}.
uint32_t ModTableSize(uint32_t x) { return x & length_bits_mask_; } uint32_t ModTableSize(uint32_t x) { return x & length_bits_mask_; }
@ -652,7 +675,7 @@ class ClockHandleTable {
const uint32_t occupancy_limit_; const uint32_t occupancy_limit_;
// Maximum total charge of all elements stored in the table. // Maximum total charge of all elements stored in the table.
const size_t capacity_; size_t capacity_;
// We partition the following members into different cache lines // We partition the following members into different cache lines
// to avoid false sharing among Lookup, Release, Erase and Insert // to avoid false sharing among Lookup, Release, Erase and Insert
@ -745,6 +768,7 @@ class ALIGN_AS(CACHE_LINE_SIZE) ClockCacheShard final : public CacheShard {
private: private:
friend class ClockCache; friend class ClockCache;
friend class ClockCacheTest;
// Free some space following strict clock policy until enough space // Free some space following strict clock policy until enough space
// to hold (usage_ + charge) is freed or there are no evictable elements. // to hold (usage_ + charge) is freed or there are no evictable elements.
@ -763,6 +787,9 @@ class ALIGN_AS(CACHE_LINE_SIZE) ClockCacheShard final : public CacheShard {
// Whether to reject insertion if cache reaches its full capacity. // Whether to reject insertion if cache reaches its full capacity.
std::atomic<bool> strict_capacity_limit_; std::atomic<bool> strict_capacity_limit_;
// Handles allocated separately from the table.
std::atomic<size_t> detached_usage_;
ClockHandleTable table_; ClockHandleTable table_;
}; // class ClockCacheShard }; // class ClockCacheShard
@ -797,6 +824,7 @@ class ClockCache
private: private:
ClockCacheShard* shards_ = nullptr; ClockCacheShard* shards_ = nullptr;
int num_shards_; int num_shards_;
}; // class ClockCache }; // class ClockCache

4
cache/fast_lru_cache.cc vendored
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@ -299,10 +299,12 @@ int LRUCacheShard::CalcHashBits(
} }
void LRUCacheShard::SetCapacity(size_t capacity) { void LRUCacheShard::SetCapacity(size_t capacity) {
assert(false); // Not supported. TODO(Guido) Support it?
autovector<LRUHandle> last_reference_list; autovector<LRUHandle> last_reference_list;
{ {
DMutexLock l(mutex_); DMutexLock l(mutex_);
if (capacity > capacity_) {
assert(false); // Not supported.
}
capacity_ = capacity; capacity_ = capacity;
EvictFromLRU(0, &last_reference_list); EvictFromLRU(0, &last_reference_list);
} }

196
cache/lru_cache_test.cc vendored
Unescape View File

@ -207,6 +207,9 @@ TEST_F(LRUCacheTest, EntriesWithPriority) {
ValidateLRUList({"e", "f", "g", "Z", "d"}, 2); ValidateLRUList({"e", "f", "g", "Z", "d"}, 2);
} }
// TODO: FastLRUCache and ClockCache use the same tests. We can probably remove
// them from FastLRUCache after ClockCache becomes productive, and we don't plan
// to use or maintain FastLRUCache any more.
namespace fast_lru_cache { namespace fast_lru_cache {
// TODO(guido) Replicate LRU policy tests from LRUCache here. // TODO(guido) Replicate LRU policy tests from LRUCache here.
@ -225,11 +228,11 @@ class FastLRUCacheTest : public testing::Test {
void NewCache(size_t capacity) { void NewCache(size_t capacity) {
DeleteCache(); DeleteCache();
cache_ = reinterpret_cast<fast_lru_cache::LRUCacheShard*>( cache_ = reinterpret_cast<LRUCacheShard*>(
port::cacheline_aligned_alloc(sizeof(fast_lru_cache::LRUCacheShard))); port::cacheline_aligned_alloc(sizeof(LRUCacheShard)));
new (cache_) fast_lru_cache::LRUCacheShard( new (cache_) LRUCacheShard(capacity, 1 /*estimated_value_size*/,
capacity, 1 /*estimated_value_size*/, false /*strict_capacity_limit*/, false /*strict_capacity_limit*/,
kDontChargeCacheMetadata); kDontChargeCacheMetadata);
} }
Status Insert(const std::string& key) { Status Insert(const std::string& key) {
@ -243,25 +246,23 @@ class FastLRUCacheTest : public testing::Test {
size_t CalcEstimatedHandleChargeWrapper( size_t CalcEstimatedHandleChargeWrapper(
size_t estimated_value_size, size_t estimated_value_size,
CacheMetadataChargePolicy metadata_charge_policy) { CacheMetadataChargePolicy metadata_charge_policy) {
return fast_lru_cache::LRUCacheShard::CalcEstimatedHandleCharge( return LRUCacheShard::CalcEstimatedHandleCharge(estimated_value_size,
estimated_value_size, metadata_charge_policy); metadata_charge_policy);
} }
int CalcHashBitsWrapper(size_t capacity, size_t estimated_value_size, int CalcHashBitsWrapper(size_t capacity, size_t estimated_value_size,
CacheMetadataChargePolicy metadata_charge_policy) { CacheMetadataChargePolicy metadata_charge_policy) {
return fast_lru_cache::LRUCacheShard::CalcHashBits( return LRUCacheShard::CalcHashBits(capacity, estimated_value_size,
capacity, estimated_value_size, metadata_charge_policy); metadata_charge_policy);
} }
// Maximum number of items that a shard can hold. // Maximum number of items that a shard can hold.
double CalcMaxOccupancy(size_t capacity, size_t estimated_value_size, double CalcMaxOccupancy(size_t capacity, size_t estimated_value_size,
CacheMetadataChargePolicy metadata_charge_policy) { CacheMetadataChargePolicy metadata_charge_policy) {
size_t handle_charge = size_t handle_charge = LRUCacheShard::CalcEstimatedHandleCharge(
fast_lru_cache::LRUCacheShard::CalcEstimatedHandleCharge( estimated_value_size, metadata_charge_policy);
estimated_value_size, metadata_charge_policy); return capacity / (kLoadFactor * handle_charge);
return capacity / (fast_lru_cache::kLoadFactor * handle_charge);
} }
bool TableSizeIsAppropriate(int hash_bits, double max_occupancy) { bool TableSizeIsAppropriate(int hash_bits, double max_occupancy) {
if (hash_bits == 0) { if (hash_bits == 0) {
return max_occupancy <= 1; return max_occupancy <= 1;
@ -272,7 +273,7 @@ class FastLRUCacheTest : public testing::Test {
} }
private: private:
fast_lru_cache::LRUCacheShard* cache_ = nullptr; LRUCacheShard* cache_ = nullptr;
}; };
TEST_F(FastLRUCacheTest, ValidateKeySize) { TEST_F(FastLRUCacheTest, ValidateKeySize) {
@ -292,7 +293,6 @@ TEST_F(FastLRUCacheTest, CalcHashBitsTest) {
double max_occupancy; double max_occupancy;
int hash_bits; int hash_bits;
CacheMetadataChargePolicy metadata_charge_policy; CacheMetadataChargePolicy metadata_charge_policy;
// Vary the cache capacity, fix the element charge. // Vary the cache capacity, fix the element charge.
for (int i = 0; i < 2048; i++) { for (int i = 0; i < 2048; i++) {
capacity = i; capacity = i;
@ -304,7 +304,6 @@ TEST_F(FastLRUCacheTest, CalcHashBitsTest) {
metadata_charge_policy); metadata_charge_policy);
EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, max_occupancy)); EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, max_occupancy));
} }
// Fix the cache capacity, vary the element charge. // Fix the cache capacity, vary the element charge.
for (int i = 0; i < 1024; i++) { for (int i = 0; i < 1024; i++) {
capacity = 1024; capacity = 1024;
@ -316,7 +315,6 @@ TEST_F(FastLRUCacheTest, CalcHashBitsTest) {
metadata_charge_policy); metadata_charge_policy);
EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, max_occupancy)); EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, max_occupancy));
} }
// Zero-capacity cache, and only values have charge. // Zero-capacity cache, and only values have charge.
capacity = 0; capacity = 0;
estimated_value_size = 1; estimated_value_size = 1;
@ -324,7 +322,6 @@ TEST_F(FastLRUCacheTest, CalcHashBitsTest) {
hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size, hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size,
metadata_charge_policy); metadata_charge_policy);
EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, 0 /* max_occupancy */)); EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, 0 /* max_occupancy */));
// Zero-capacity cache, and only metadata has charge. // Zero-capacity cache, and only metadata has charge.
capacity = 0; capacity = 0;
estimated_value_size = 0; estimated_value_size = 0;
@ -332,7 +329,6 @@ TEST_F(FastLRUCacheTest, CalcHashBitsTest) {
hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size, hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size,
metadata_charge_policy); metadata_charge_policy);
EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, 0 /* max_occupancy */)); EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, 0 /* max_occupancy */));
// Small cache, large elements. // Small cache, large elements.
capacity = 1024; capacity = 1024;
estimated_value_size = 8192; estimated_value_size = 8192;
@ -340,7 +336,6 @@ TEST_F(FastLRUCacheTest, CalcHashBitsTest) {
hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size, hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size,
metadata_charge_policy); metadata_charge_policy);
EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, 0 /* max_occupancy */)); EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, 0 /* max_occupancy */));
// Large capacity. // Large capacity.
capacity = 31924172; capacity = 31924172;
estimated_value_size = 8192; estimated_value_size = 8192;
@ -402,37 +397,38 @@ class ClockCacheTest : public testing::Test {
void Erase(const std::string& key) { shard_->Erase(key, 0 /*hash*/); } void Erase(const std::string& key) { shard_->Erase(key, 0 /*hash*/); }
// void ValidateLRUList(std::vector<std::string> keys, size_t CalcEstimatedHandleChargeWrapper(
// size_t num_high_pri_pool_keys = 0) { size_t estimated_value_size,
// LRUHandle* lru; CacheMetadataChargePolicy metadata_charge_policy) {
// LRUHandle* lru_low_pri; return ClockCacheShard::CalcEstimatedHandleCharge(estimated_value_size,
// cache_->TEST_GetLRUList(&lru, &lru_low_pri); metadata_charge_policy);
// LRUHandle* iter = lru; }
// bool in_high_pri_pool = false;
// size_t high_pri_pool_keys = 0; int CalcHashBitsWrapper(size_t capacity, size_t estimated_value_size,
// if (iter == lru_low_pri) { CacheMetadataChargePolicy metadata_charge_policy) {
// in_high_pri_pool = true; return ClockCacheShard::CalcHashBits(capacity, estimated_value_size,
// } metadata_charge_policy);
// for (const auto& key : keys) { }
// iter = iter->next;
// ASSERT_NE(lru, iter); // Maximum number of items that a shard can hold.
// ASSERT_EQ(key, iter->key().ToString()); double CalcMaxOccupancy(size_t capacity, size_t estimated_value_size,
// ASSERT_EQ(in_high_pri_pool, iter->InHighPriPool()); CacheMetadataChargePolicy metadata_charge_policy) {
// if (in_high_pri_pool) { size_t handle_charge = ClockCacheShard::CalcEstimatedHandleCharge(
// high_pri_pool_keys++; estimated_value_size, metadata_charge_policy);
// } return capacity / (kLoadFactor * handle_charge);
// if (iter == lru_low_pri) { }
// ASSERT_FALSE(in_high_pri_pool);
// in_high_pri_pool = true; bool TableSizeIsAppropriate(int hash_bits, double max_occupancy) {
// } if (hash_bits == 0) {
// } return max_occupancy <= 1;
// ASSERT_EQ(lru, iter->next); } else {
// ASSERT_TRUE(in_high_pri_pool); return (1 << hash_bits >= max_occupancy) &&
// ASSERT_EQ(num_high_pri_pool_keys, high_pri_pool_keys); (1 << (hash_bits - 1) <= max_occupancy);
// } }
}
private: private:
clock_cache::ClockCacheShard* shard_ = nullptr; ClockCacheShard* shard_ = nullptr;
}; };
TEST_F(ClockCacheTest, Validate) { TEST_F(ClockCacheTest, Validate) {
@ -447,31 +443,89 @@ TEST_F(ClockCacheTest, Validate) {
} }
TEST_F(ClockCacheTest, ClockPriorityTest) { TEST_F(ClockCacheTest, ClockPriorityTest) {
clock_cache::ClockHandle handle; ClockHandle handle;
EXPECT_EQ(handle.GetClockPriority(), EXPECT_EQ(handle.GetClockPriority(), ClockHandle::ClockPriority::NONE);
clock_cache::ClockHandle::ClockPriority::NONE); handle.SetClockPriority(ClockHandle::ClockPriority::HIGH);
handle.SetClockPriority(clock_cache::ClockHandle::ClockPriority::HIGH); EXPECT_EQ(handle.GetClockPriority(), ClockHandle::ClockPriority::HIGH);
EXPECT_EQ(handle.GetClockPriority(),
clock_cache::ClockHandle::ClockPriority::HIGH);
handle.DecreaseClockPriority(); handle.DecreaseClockPriority();
EXPECT_EQ(handle.GetClockPriority(), EXPECT_EQ(handle.GetClockPriority(), ClockHandle::ClockPriority::MEDIUM);
clock_cache::ClockHandle::ClockPriority::MEDIUM);
handle.DecreaseClockPriority(); handle.DecreaseClockPriority();
EXPECT_EQ(handle.GetClockPriority(), EXPECT_EQ(handle.GetClockPriority(), ClockHandle::ClockPriority::LOW);
clock_cache::ClockHandle::ClockPriority::LOW); handle.SetClockPriority(ClockHandle::ClockPriority::MEDIUM);
handle.SetClockPriority(clock_cache::ClockHandle::ClockPriority::MEDIUM); EXPECT_EQ(handle.GetClockPriority(), ClockHandle::ClockPriority::MEDIUM);
EXPECT_EQ(handle.GetClockPriority(), handle.SetClockPriority(ClockHandle::ClockPriority::NONE);
clock_cache::ClockHandle::ClockPriority::MEDIUM); EXPECT_EQ(handle.GetClockPriority(), ClockHandle::ClockPriority::NONE);
handle.SetClockPriority(clock_cache::ClockHandle::ClockPriority::NONE); handle.SetClockPriority(ClockHandle::ClockPriority::MEDIUM);
EXPECT_EQ(handle.GetClockPriority(), EXPECT_EQ(handle.GetClockPriority(), ClockHandle::ClockPriority::MEDIUM);
clock_cache::ClockHandle::ClockPriority::NONE);
handle.SetClockPriority(clock_cache::ClockHandle::ClockPriority::MEDIUM);
EXPECT_EQ(handle.GetClockPriority(),
clock_cache::ClockHandle::ClockPriority::MEDIUM);
handle.DecreaseClockPriority(); handle.DecreaseClockPriority();
handle.DecreaseClockPriority(); handle.DecreaseClockPriority();
EXPECT_EQ(handle.GetClockPriority(), EXPECT_EQ(handle.GetClockPriority(), ClockHandle::ClockPriority::NONE);
clock_cache::ClockHandle::ClockPriority::NONE); }
TEST_F(ClockCacheTest, CalcHashBitsTest) {
size_t capacity;
size_t estimated_value_size;
double max_occupancy;
int hash_bits;
CacheMetadataChargePolicy metadata_charge_policy;
// Vary the cache capacity, fix the element charge.
for (int i = 0; i < 2048; i++) {
capacity = i;
estimated_value_size = 0;
metadata_charge_policy = kFullChargeCacheMetadata;
max_occupancy = CalcMaxOccupancy(capacity, estimated_value_size,
metadata_charge_policy);
hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size,
metadata_charge_policy);
EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, max_occupancy));
}
// Fix the cache capacity, vary the element charge.
for (int i = 0; i < 1024; i++) {
capacity = 1024;
estimated_value_size = i;
metadata_charge_policy = kFullChargeCacheMetadata;
max_occupancy = CalcMaxOccupancy(capacity, estimated_value_size,
metadata_charge_policy);
hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size,
metadata_charge_policy);
EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, max_occupancy));
}
// Zero-capacity cache, and only values have charge.
capacity = 0;
estimated_value_size = 1;
metadata_charge_policy = kDontChargeCacheMetadata;
hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size,
metadata_charge_policy);
EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, 0 /* max_occupancy */));
// Zero-capacity cache, and only metadata has charge.
capacity = 0;
estimated_value_size = 0;
metadata_charge_policy = kFullChargeCacheMetadata;
hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size,
metadata_charge_policy);
EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, 0 /* max_occupancy */));
// Small cache, large elements.
capacity = 1024;
estimated_value_size = 8192;
metadata_charge_policy = kFullChargeCacheMetadata;
hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size,
metadata_charge_policy);
EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, 0 /* max_occupancy */));
// Large capacity.
capacity = 31924172;
estimated_value_size = 8192;
metadata_charge_policy = kFullChargeCacheMetadata;
max_occupancy =
CalcMaxOccupancy(capacity, estimated_value_size, metadata_charge_policy);
hash_bits = CalcHashBitsWrapper(capacity, estimated_value_size,
metadata_charge_policy);
EXPECT_TRUE(TableSizeIsAppropriate(hash_bits, max_occupancy));
} }
} // namespace clock_cache } // namespace clock_cache

4
tools/db_crashtest.py
Unescape View File

@ -116,8 +116,8 @@ default_params = {
"use_direct_reads": lambda: random.randint(0, 1), "use_direct_reads": lambda: random.randint(0, 1),
"use_direct_io_for_flush_and_compaction": lambda: random.randint(0, 1), "use_direct_io_for_flush_and_compaction": lambda: random.randint(0, 1),
"mock_direct_io": False, "mock_direct_io": False,
"cache_type": "lru_cache", # fast_lru_cache and clock_cache are currently incompatible "cache_type": lambda: random.choice(["lru_cache", "clock_cache"]),
# with stress tests, because they use strict_capacity_limit = false # fast_lru_cache is incompatible with stress tests, because it doesn't support strict_capacity_limit == false.
"use_full_merge_v1": lambda: random.randint(0, 1), "use_full_merge_v1": lambda: random.randint(0, 1),
"use_merge": lambda: random.randint(0, 1), "use_merge": lambda: random.randint(0, 1),
# 999 -> use Bloom API # 999 -> use Bloom API

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