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rocksdb/cache/cache_reservation_manager_test.cc
Peter Dillinger 0050a73a4f New stable, fixed-length cache keys (#9126) 
Summary:
This change standardizes on a new 16-byte cache key format for
block cache (incl compressed and secondary) and persistent cache (but
not table cache and row cache).

The goal is a really fast cache key with practically ideal stability and
uniqueness properties without external dependencies (e.g. from FileSystem).
A fixed key size of 16 bytes should enable future optimizations to the
concurrent hash table for block cache, which is a heavy CPU user /
bottleneck, but there appears to be measurable performance improvement
even with no changes to LRUCache.

This change replaces a lot of disjointed and ugly code handling cache
keys with calls to a simple, clean new internal API (cache_key.h).
(Preserving the old cache key logic under an option would be very ugly
and likely negate the performance gain of the new approach. Complete
replacement carries some inherent risk, but I think that's acceptable
with sufficient analysis and testing.)

The scheme for encoding new cache keys is complicated but explained
in cache_key.cc.

Also: EndianSwapValue is moved to math.h to be next to other bit
operations. (Explains some new include "math.h".) ReverseBits operation
added and unit tests added to hash_test for both.

Fixes https://github.com/facebook/rocksdb/issues/7405 (presuming a root cause)

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9126

Test Plan:
### Basic correctness
Several tests needed updates to work with the new functionality, mostly
because we are no longer relying on filesystem for stable cache keys
so table builders & readers need more context info to agree on cache
keys. This functionality is so core, a huge number of existing tests
exercise the cache key functionality.

### Performance
Create db with
`TEST_TMPDIR=/dev/shm ./db_bench -bloom_bits=10 -benchmarks=fillrandom -num=3000000 -partition_index_and_filters`
And test performance with
`TEST_TMPDIR=/dev/shm ./db_bench -readonly -use_existing_db -bloom_bits=10 -benchmarks=readrandom -num=3000000 -duration=30 -cache_index_and_filter_blocks -cache_size=250000 -threads=4`
using DEBUG_LEVEL=0 and simultaneous before & after runs.
Before ops/sec, avg over 100 runs: 121924
After ops/sec, avg over 100 runs: 125385 (+2.8%)

### Collision probability
I have built a tool, ./cache_bench -stress_cache_key to broadly simulate host-wide cache activity
over many months, by making some pessimistic simplifying assumptions:
* Every generated file has a cache entry for every byte offset in the file (contiguous range of cache keys)
* All of every file is cached for its entire lifetime

We use a simple table with skewed address assignment and replacement on address collision
to simulate files coming & going, with quite a variance (super-Poisson) in ages. Some output
with `./cache_bench -stress_cache_key -sck_keep_bits=40`:

```
Total cache or DBs size: 32TiB  Writing 925.926 MiB/s or 76.2939TiB/day
Multiply by 9.22337e+18 to correct for simulation losses (but still assume whole file cached)
```

These come from default settings of 2.5M files per day of 32 MB each, and
`-sck_keep_bits=40` means that to represent a single file, we are only keeping 40 bits of
the 128-bit cache key.  With file size of 2\*\*25 contiguous keys (pessimistic), our simulation
is about 2\*\*(128-40-25) or about 9 billion billion times more prone to collision than reality.

More default assumptions, relatively pessimistic:
* 100 DBs in same process (doesn't matter much)
* Re-open DB in same process (new session ID related to old session ID) on average
every 100 files generated
* Restart process (all new session IDs unrelated to old) 24 times per day

After enough data, we get a result at the end:

```
(keep 40 bits)  17 collisions after 2 x 90 days, est 10.5882 days between (9.76592e+19 corrected)
```

If we believe the (pessimistic) simulation and the mathematical generalization, we would need to run a billion machines all for 97 billion days to expect a cache key collision. To help verify that our generalization ("corrected") is robust, we can make our simulation more precise with `-sck_keep_bits=41` and `42`, which takes more running time to get enough data:

```
(keep 41 bits)  16 collisions after 4 x 90 days, est 22.5 days between (1.03763e+20 corrected)
(keep 42 bits)  19 collisions after 10 x 90 days, est 47.3684 days between (1.09224e+20 corrected)
```

The generalized prediction still holds. With the `-sck_randomize` option, we can see that we are beating "random" cache keys (except offsets still non-randomized) by a modest amount (roughly 20x less collision prone than random), which should make us reasonably comfortable even in "degenerate" cases:

```
197 collisions after 1 x 90 days, est 0.456853 days between (4.21372e+18 corrected)
```

I've run other tests to validate other conditions behave as expected, never behaving "worse than random" unless we start chopping off structured data.

Reviewed By: zhichao-cao

Differential Revision: D33171746

Pulled By: pdillinger

fbshipit-source-id: f16a57e369ed37be5e7e33525ace848d0537c88f
2021-12-16 17:15:13 -08:00

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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).
//
// 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 "cache/cache_reservation_manager.h"
#include <cstddef>
#include <cstring>
#include <memory>
#include "cache/cache_entry_roles.h"
#include "rocksdb/cache.h"
#include "rocksdb/slice.h"
#include "table/block_based/block_based_table_reader.h"
#include "test_util/testharness.h"
#include "util/coding.h"
namespace ROCKSDB_NAMESPACE {
class CacheReservationManagerTest : public ::testing::Test {
protected:
static constexpr std::size_t kSizeDummyEntry =
CacheReservationManager::GetDummyEntrySize();
static constexpr std::size_t kCacheCapacity = 4096 * kSizeDummyEntry;
static constexpr int kNumShardBits = 0; // 2^0 shard
static constexpr std::size_t kMetaDataChargeOverhead = 10000;
std::shared_ptr<Cache> cache = NewLRUCache(kCacheCapacity, kNumShardBits);
std::unique_ptr<CacheReservationManager> test_cache_rev_mng;
CacheReservationManagerTest() {
test_cache_rev_mng.reset(new CacheReservationManager(cache));
}
};
TEST_F(CacheReservationManagerTest, GenerateCacheKey) {
std::size_t new_mem_used = 1 * kSizeDummyEntry;
Status s =
test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
ASSERT_EQ(s, Status::OK());
ASSERT_GE(cache->GetPinnedUsage(), 1 * kSizeDummyEntry);
ASSERT_LT(cache->GetPinnedUsage(),
1 * kSizeDummyEntry + kMetaDataChargeOverhead);
// Next unique Cache key
CacheKey ckey = CacheKey::CreateUniqueForCacheLifetime(cache.get());
// Back it up to the one used by CRM (using CacheKey implementation details)
using PairU64 = std::pair<uint64_t, uint64_t>;
auto& ckey_pair = *reinterpret_cast<PairU64*>(&ckey);
ckey_pair.second--;
// Specific key (subject to implementation details)
EXPECT_EQ(ckey_pair, PairU64(0, 2));
Cache::Handle* handle = cache->Lookup(ckey.AsSlice());
EXPECT_NE(handle, nullptr)
<< "Failed to generate the cache key for the dummy entry correctly";
// Clean up the returned handle from Lookup() to prevent memory leak
cache->Release(handle);
}
TEST_F(CacheReservationManagerTest, KeepCacheReservationTheSame) {
std::size_t new_mem_used = 1 * kSizeDummyEntry;
Status s =
test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
ASSERT_EQ(s, Status::OK());
ASSERT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
1 * kSizeDummyEntry);
ASSERT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used);
std::size_t initial_pinned_usage = cache->GetPinnedUsage();
ASSERT_GE(initial_pinned_usage, 1 * kSizeDummyEntry);
ASSERT_LT(initial_pinned_usage,
1 * kSizeDummyEntry + kMetaDataChargeOverhead);
s = test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::OK())
<< "Failed to keep cache reservation the same when new_mem_used equals "
"to current cache reservation";
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
1 * kSizeDummyEntry)
<< "Failed to bookkeep correctly when new_mem_used equals to current "
"cache reservation";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly when new_mem_used "
"equals to current cache reservation";
EXPECT_EQ(cache->GetPinnedUsage(), initial_pinned_usage)
<< "Failed to keep underlying dummy entries the same when new_mem_used "
"equals to current cache reservation";
}
TEST_F(CacheReservationManagerTest,
IncreaseCacheReservationByMultiplesOfDummyEntrySize) {
std::size_t new_mem_used = 2 * kSizeDummyEntry;
Status s =
test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::OK())
<< "Failed to increase cache reservation correctly";
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
2 * kSizeDummyEntry)
<< "Failed to bookkeep cache reservation increase correctly";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly";
EXPECT_GE(cache->GetPinnedUsage(), 2 * kSizeDummyEntry)
<< "Failed to increase underlying dummy entries in cache correctly";
EXPECT_LT(cache->GetPinnedUsage(),
2 * kSizeDummyEntry + kMetaDataChargeOverhead)
<< "Failed to increase underlying dummy entries in cache correctly";
}
TEST_F(CacheReservationManagerTest,
IncreaseCacheReservationNotByMultiplesOfDummyEntrySize) {
std::size_t new_mem_used = 2 * kSizeDummyEntry + kSizeDummyEntry / 2;
Status s =
test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::OK())
<< "Failed to increase cache reservation correctly";
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
3 * kSizeDummyEntry)
<< "Failed to bookkeep cache reservation increase correctly";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly";
EXPECT_GE(cache->GetPinnedUsage(), 3 * kSizeDummyEntry)
<< "Failed to increase underlying dummy entries in cache correctly";
EXPECT_LT(cache->GetPinnedUsage(),
3 * kSizeDummyEntry + kMetaDataChargeOverhead)
<< "Failed to increase underlying dummy entries in cache correctly";
}
TEST(CacheReservationManagerIncreaseReservcationOnFullCacheTest,
IncreaseCacheReservationOnFullCache) {
;
constexpr std::size_t kSizeDummyEntry =
CacheReservationManager::GetDummyEntrySize();
constexpr std::size_t kSmallCacheCapacity = 4 * kSizeDummyEntry;
constexpr std::size_t kBigCacheCapacity = 4096 * kSizeDummyEntry;
constexpr std::size_t kMetaDataChargeOverhead = 10000;
LRUCacheOptions lo;
lo.capacity = kSmallCacheCapacity;
lo.num_shard_bits = 0; // 2^0 shard
lo.strict_capacity_limit = true;
std::shared_ptr<Cache> cache = NewLRUCache(lo);
std::unique_ptr<CacheReservationManager> test_cache_rev_mng(
new CacheReservationManager(cache));
std::size_t new_mem_used = kSmallCacheCapacity + 1;
Status s =
test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::Incomplete())
<< "Failed to return status to indicate failure of dummy entry insertion "
"during cache reservation on full cache";
EXPECT_GE(test_cache_rev_mng->GetTotalReservedCacheSize(),
1 * kSizeDummyEntry)
<< "Failed to bookkeep correctly before cache resevation failure happens "
"due to full cache";
EXPECT_LE(test_cache_rev_mng->GetTotalReservedCacheSize(),
kSmallCacheCapacity)
<< "Failed to bookkeep correctly (i.e, bookkeep only successful dummy "
"entry insertions) when encountering cache resevation failure due to "
"full cache";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly";
EXPECT_GE(cache->GetPinnedUsage(), 1 * kSizeDummyEntry)
<< "Failed to insert underlying dummy entries correctly when "
"encountering cache resevation failure due to full cache";
EXPECT_LE(cache->GetPinnedUsage(), kSmallCacheCapacity)
<< "Failed to insert underlying dummy entries correctly when "
"encountering cache resevation failure due to full cache";
new_mem_used = kSmallCacheCapacity / 2; // 2 dummy entries
s = test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::OK())
<< "Failed to decrease cache reservation after encountering cache "
"reservation failure due to full cache";
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
2 * kSizeDummyEntry)
<< "Failed to bookkeep cache reservation decrease correctly after "
"encountering cache reservation due to full cache";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly";
EXPECT_GE(cache->GetPinnedUsage(), 2 * kSizeDummyEntry)
<< "Failed to release underlying dummy entries correctly on cache "
"reservation decrease after encountering cache resevation failure due "
"to full cache";
EXPECT_LT(cache->GetPinnedUsage(),
2 * kSizeDummyEntry + kMetaDataChargeOverhead)
<< "Failed to release underlying dummy entries correctly on cache "
"reservation decrease after encountering cache resevation failure due "
"to full cache";
// Create cache full again for subsequent tests
new_mem_used = kSmallCacheCapacity + 1;
s = test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::Incomplete())
<< "Failed to return status to indicate failure of dummy entry insertion "
"during cache reservation on full cache";
EXPECT_GE(test_cache_rev_mng->GetTotalReservedCacheSize(),
1 * kSizeDummyEntry)
<< "Failed to bookkeep correctly before cache resevation failure happens "
"due to full cache";
EXPECT_LE(test_cache_rev_mng->GetTotalReservedCacheSize(),
kSmallCacheCapacity)
<< "Failed to bookkeep correctly (i.e, bookkeep only successful dummy "
"entry insertions) when encountering cache resevation failure due to "
"full cache";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly";
EXPECT_GE(cache->GetPinnedUsage(), 1 * kSizeDummyEntry)
<< "Failed to insert underlying dummy entries correctly when "
"encountering cache resevation failure due to full cache";
EXPECT_LE(cache->GetPinnedUsage(), kSmallCacheCapacity)
<< "Failed to insert underlying dummy entries correctly when "
"encountering cache resevation failure due to full cache";
// Increase cache capacity so the previously failed insertion can fully
// succeed
cache->SetCapacity(kBigCacheCapacity);
new_mem_used = kSmallCacheCapacity + 1;
s = test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::OK())
<< "Failed to increase cache reservation after increasing cache capacity "
"and mitigating cache full error";
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
5 * kSizeDummyEntry)
<< "Failed to bookkeep cache reservation increase correctly after "
"increasing cache capacity and mitigating cache full error";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly";
EXPECT_GE(cache->GetPinnedUsage(), 5 * kSizeDummyEntry)
<< "Failed to insert underlying dummy entries correctly after increasing "
"cache capacity and mitigating cache full error";
EXPECT_LT(cache->GetPinnedUsage(),
5 * kSizeDummyEntry + kMetaDataChargeOverhead)
<< "Failed to insert underlying dummy entries correctly after increasing "
"cache capacity and mitigating cache full error";
}
TEST_F(CacheReservationManagerTest,
DecreaseCacheReservationByMultiplesOfDummyEntrySize) {
std::size_t new_mem_used = 2 * kSizeDummyEntry;
Status s =
test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
ASSERT_EQ(s, Status::OK());
ASSERT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
2 * kSizeDummyEntry);
ASSERT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used);
ASSERT_GE(cache->GetPinnedUsage(), 2 * kSizeDummyEntry);
ASSERT_LT(cache->GetPinnedUsage(),
2 * kSizeDummyEntry + kMetaDataChargeOverhead);
new_mem_used = 1 * kSizeDummyEntry;
s = test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::OK())
<< "Failed to decrease cache reservation correctly";
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
1 * kSizeDummyEntry)
<< "Failed to bookkeep cache reservation decrease correctly";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly";
EXPECT_GE(cache->GetPinnedUsage(), 1 * kSizeDummyEntry)
<< "Failed to decrease underlying dummy entries in cache correctly";
EXPECT_LT(cache->GetPinnedUsage(),
1 * kSizeDummyEntry + kMetaDataChargeOverhead)
<< "Failed to decrease underlying dummy entries in cache correctly";
}
TEST_F(CacheReservationManagerTest,
DecreaseCacheReservationNotByMultiplesOfDummyEntrySize) {
std::size_t new_mem_used = 2 * kSizeDummyEntry;
Status s =
test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
ASSERT_EQ(s, Status::OK());
ASSERT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
2 * kSizeDummyEntry);
ASSERT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used);
ASSERT_GE(cache->GetPinnedUsage(), 2 * kSizeDummyEntry);
ASSERT_LT(cache->GetPinnedUsage(),
2 * kSizeDummyEntry + kMetaDataChargeOverhead);
new_mem_used = kSizeDummyEntry / 2;
s = test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::OK())
<< "Failed to decrease cache reservation correctly";
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
1 * kSizeDummyEntry)
<< "Failed to bookkeep cache reservation decrease correctly";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly";
EXPECT_GE(cache->GetPinnedUsage(), 1 * kSizeDummyEntry)
<< "Failed to decrease underlying dummy entries in cache correctly";
EXPECT_LT(cache->GetPinnedUsage(),
1 * kSizeDummyEntry + kMetaDataChargeOverhead)
<< "Failed to decrease underlying dummy entries in cache correctly";
}
TEST(CacheReservationManagerWithDelayedDecreaseTest,
DecreaseCacheReservationWithDelayedDecrease) {
constexpr std::size_t kSizeDummyEntry =
CacheReservationManager::GetDummyEntrySize();
constexpr std::size_t kCacheCapacity = 4096 * kSizeDummyEntry;
constexpr std::size_t kMetaDataChargeOverhead = 10000;
LRUCacheOptions lo;
lo.capacity = kCacheCapacity;
lo.num_shard_bits = 0;
std::shared_ptr<Cache> cache = NewLRUCache(lo);
std::unique_ptr<CacheReservationManager> test_cache_rev_mng(
new CacheReservationManager(cache, true /* delayed_decrease */));
std::size_t new_mem_used = 8 * kSizeDummyEntry;
Status s =
test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
ASSERT_EQ(s, Status::OK());
ASSERT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
8 * kSizeDummyEntry);
ASSERT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used);
std::size_t initial_pinned_usage = cache->GetPinnedUsage();
ASSERT_GE(initial_pinned_usage, 8 * kSizeDummyEntry);
ASSERT_LT(initial_pinned_usage,
8 * kSizeDummyEntry + kMetaDataChargeOverhead);
new_mem_used = 6 * kSizeDummyEntry;
s = test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::OK()) << "Failed to delay decreasing cache reservation";
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
8 * kSizeDummyEntry)
<< "Failed to bookkeep correctly when delaying cache reservation "
"decrease";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly";
EXPECT_EQ(cache->GetPinnedUsage(), initial_pinned_usage)
<< "Failed to delay decreasing underlying dummy entries in cache";
new_mem_used = 7 * kSizeDummyEntry;
s = test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::OK()) << "Failed to delay decreasing cache reservation";
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
8 * kSizeDummyEntry)
<< "Failed to bookkeep correctly when delaying cache reservation "
"decrease";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly";
EXPECT_EQ(cache->GetPinnedUsage(), initial_pinned_usage)
<< "Failed to delay decreasing underlying dummy entries in cache";
new_mem_used = 6 * kSizeDummyEntry - 1;
s = test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
EXPECT_EQ(s, Status::OK())
<< "Failed to decrease cache reservation correctly when new_mem_used < "
"GetTotalReservedCacheSize() * 3 / 4 on delayed decrease mode";
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(),
6 * kSizeDummyEntry)
<< "Failed to bookkeep correctly when new_mem_used < "
"GetTotalReservedCacheSize() * 3 / 4 on delayed decrease mode";
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), new_mem_used)
<< "Failed to bookkeep the used memory correctly";
EXPECT_GE(cache->GetPinnedUsage(), 6 * kSizeDummyEntry)
<< "Failed to decrease underlying dummy entries in cache when "
"new_mem_used < GetTotalReservedCacheSize() * 3 / 4 on delayed "
"decrease mode";
EXPECT_LT(cache->GetPinnedUsage(),
6 * kSizeDummyEntry + kMetaDataChargeOverhead)
<< "Failed to decrease underlying dummy entries in cache when "
"new_mem_used < GetTotalReservedCacheSize() * 3 / 4 on delayed "
"decrease mode";
}
TEST(CacheReservationManagerDestructorTest,
ReleaseRemainingDummyEntriesOnDestruction) {
constexpr std::size_t kSizeDummyEntry =
CacheReservationManager::GetDummyEntrySize();
constexpr std::size_t kCacheCapacity = 4096 * kSizeDummyEntry;
constexpr std::size_t kMetaDataChargeOverhead = 10000;
LRUCacheOptions lo;
lo.capacity = kCacheCapacity;
lo.num_shard_bits = 0;
std::shared_ptr<Cache> cache = NewLRUCache(lo);
{
std::unique_ptr<CacheReservationManager> test_cache_rev_mng(
new CacheReservationManager(cache));
std::size_t new_mem_used = 1 * kSizeDummyEntry;
Status s =
test_cache_rev_mng
->UpdateCacheReservation<ROCKSDB_NAMESPACE::CacheEntryRole::kMisc>(
new_mem_used);
ASSERT_EQ(s, Status::OK());
ASSERT_GE(cache->GetPinnedUsage(), 1 * kSizeDummyEntry);
ASSERT_LT(cache->GetPinnedUsage(),
1 * kSizeDummyEntry + kMetaDataChargeOverhead);
}
EXPECT_EQ(cache->GetPinnedUsage(), 0 * kSizeDummyEntry)
<< "Failed to release remaining underlying dummy entries in cache in "
"CacheReservationManager's destructor";
}
TEST(CacheReservationHandleTest, HandleTest) {
constexpr std::size_t kOneGigabyte = 1024 * 1024 * 1024;
constexpr std::size_t kSizeDummyEntry = 256 * 1024;
constexpr std::size_t kMetaDataChargeOverhead = 10000;
LRUCacheOptions lo;
lo.capacity = kOneGigabyte;
lo.num_shard_bits = 0;
std::shared_ptr<Cache> cache = NewLRUCache(lo);
std::shared_ptr<CacheReservationManager> test_cache_rev_mng(
std::make_shared<CacheReservationManager>(cache));
std::size_t mem_used = 0;
const std::size_t incremental_mem_used_handle_1 = 1 * kSizeDummyEntry;
const std::size_t incremental_mem_used_handle_2 = 2 * kSizeDummyEntry;
std::unique_ptr<CacheReservationHandle<CacheEntryRole::kMisc>> handle_1,
handle_2;
// To test consecutive CacheReservationManager::MakeCacheReservation works
// correctly in terms of returning the handle as well as updating cache
// reservation and the latest total memory used
Status s = test_cache_rev_mng->MakeCacheReservation<CacheEntryRole::kMisc>(
incremental_mem_used_handle_1, &handle_1);
mem_used = mem_used + incremental_mem_used_handle_1;
ASSERT_EQ(s, Status::OK());
EXPECT_TRUE(handle_1 != nullptr);
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(), mem_used);
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), mem_used);
EXPECT_GE(cache->GetPinnedUsage(), mem_used);
EXPECT_LT(cache->GetPinnedUsage(), mem_used + kMetaDataChargeOverhead);
s = test_cache_rev_mng->MakeCacheReservation<CacheEntryRole::kMisc>(
incremental_mem_used_handle_2, &handle_2);
mem_used = mem_used + incremental_mem_used_handle_2;
ASSERT_EQ(s, Status::OK());
EXPECT_TRUE(handle_2 != nullptr);
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(), mem_used);
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), mem_used);
EXPECT_GE(cache->GetPinnedUsage(), mem_used);
EXPECT_LT(cache->GetPinnedUsage(), mem_used + kMetaDataChargeOverhead);
// To test CacheReservationHandle::~CacheReservationHandle() works correctly
// in releasing the cache reserved for the handle
handle_1.reset();
EXPECT_TRUE(handle_1 == nullptr);
mem_used = mem_used - incremental_mem_used_handle_1;
EXPECT_EQ(test_cache_rev_mng->GetTotalReservedCacheSize(), mem_used);
EXPECT_EQ(test_cache_rev_mng->GetTotalMemoryUsed(), mem_used);
EXPECT_GE(cache->GetPinnedUsage(), mem_used);
EXPECT_LT(cache->GetPinnedUsage(), mem_used + kMetaDataChargeOverhead);
// To test the actual CacheReservationManager object won't be deallocated
// as long as there remain handles pointing to it.
// We strongly recommend deallocating CacheReservationManager object only
// after all its handles are deallocated to keep things easy to reasonate
test_cache_rev_mng.reset();
EXPECT_GE(cache->GetPinnedUsage(), mem_used);
EXPECT_LT(cache->GetPinnedUsage(), mem_used + kMetaDataChargeOverhead);
handle_2.reset();
// The CacheReservationManager object is now deallocated since all the handles
// and its original pointer is gone
mem_used = mem_used - incremental_mem_used_handle_2;
EXPECT_EQ(mem_used, 0);
EXPECT_EQ(cache->GetPinnedUsage(), mem_used);
}
} // namespace ROCKSDB_NAMESPACE
int main(int argc, char** argv) {
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}
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