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269478ee46
Summary: This PR implements support for a three tier cache - primary block cache, compressed secondary cache, and a nvm (local flash) secondary cache. This allows more effective utilization of the nvm cache, and minimizes the number of reads from local flash by caching compressed blocks in the compressed secondary cache. The basic design is as follows - 1. A new secondary cache implementation, ```TieredSecondaryCache```, is introduced. It keeps the compressed and nvm secondary caches and manages the movement of blocks between them and the primary block cache. To setup a three tier cache, we allocate a ```CacheWithSecondaryAdapter```, with a ```TieredSecondaryCache``` instance as the secondary cache. 2. The table reader passes both the uncompressed and compressed block to ```FullTypedCacheInterface::InsertFull```, allowing the block cache to optionally store the compressed block. 3. When there's a miss, the block object is constructed and inserted in the primary cache, and the compressed block is inserted into the nvm cache by calling ```InsertSaved```. This avoids the overhead of recompressing the block, as well as avoiding putting more memory pressure on the compressed secondary cache. 4. When there's a hit in the nvm cache, we attempt to insert the block in the compressed secondary cache and the primary cache, subject to the admission policy of those caches (i.e admit on second access). Blocks/items evicted from any tier are simply discarded. We can easily implement additional admission policies if desired. Todo (In a subsequent PR): 1. Add to db_bench and run benchmarks 2. Add to db_stress Pull Request resolved: https://github.com/facebook/rocksdb/pull/11812 Reviewed By: pdillinger Differential Revision: D49461842 Pulled By: anand1976 fbshipit-source-id: b40ac1330ef7cd8c12efa0a3ca75128e602e3a0b
112 lines
4.1 KiB
C++
112 lines
4.1 KiB
C++
// Copyright (c) Meta Platforms, Inc. and affiliates.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#include "cache/charged_cache.h"
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#include "cache/cache_reservation_manager.h"
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namespace ROCKSDB_NAMESPACE {
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ChargedCache::ChargedCache(std::shared_ptr<Cache> cache,
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std::shared_ptr<Cache> block_cache)
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: CacheWrapper(cache),
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cache_res_mgr_(std::make_shared<ConcurrentCacheReservationManager>(
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std::make_shared<
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CacheReservationManagerImpl<CacheEntryRole::kBlobCache>>(
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block_cache))) {}
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Status ChargedCache::Insert(const Slice& key, ObjectPtr obj,
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const CacheItemHelper* helper, size_t charge,
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Handle** handle, Priority priority,
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const Slice& compressed_val, CompressionType type) {
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Status s = target_->Insert(key, obj, helper, charge, handle, priority,
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compressed_val, type);
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if (s.ok()) {
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// Insert may cause the cache entry eviction if the cache is full. So we
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// directly call the reservation manager to update the total memory used
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// in the cache.
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assert(cache_res_mgr_);
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cache_res_mgr_->UpdateCacheReservation(target_->GetUsage())
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.PermitUncheckedError();
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}
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return s;
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}
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Cache::Handle* ChargedCache::Lookup(const Slice& key,
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const CacheItemHelper* helper,
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CreateContext* create_context,
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Priority priority, Statistics* stats) {
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auto handle = target_->Lookup(key, helper, create_context, priority, stats);
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// Lookup may promote the KV pair from the secondary cache to the primary
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// cache. So we directly call the reservation manager to update the total
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// memory used in the cache.
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if (helper && helper->create_cb) {
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assert(cache_res_mgr_);
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cache_res_mgr_->UpdateCacheReservation(target_->GetUsage())
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.PermitUncheckedError();
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}
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return handle;
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}
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void ChargedCache::WaitAll(AsyncLookupHandle* async_handles, size_t count) {
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target_->WaitAll(async_handles, count);
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// In case of any promotions. Although some could finish by return of
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// StartAsyncLookup, Wait/WaitAll will generally be used, so simpler to
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// update here.
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assert(cache_res_mgr_);
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cache_res_mgr_->UpdateCacheReservation(target_->GetUsage())
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.PermitUncheckedError();
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}
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bool ChargedCache::Release(Cache::Handle* handle, bool useful,
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bool erase_if_last_ref) {
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size_t memory_used_delta = target_->GetUsage(handle);
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bool erased = target_->Release(handle, useful, erase_if_last_ref);
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if (erased) {
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assert(cache_res_mgr_);
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cache_res_mgr_
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->UpdateCacheReservation(memory_used_delta, /* increase */ false)
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.PermitUncheckedError();
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}
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return erased;
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}
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bool ChargedCache::Release(Cache::Handle* handle, bool erase_if_last_ref) {
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size_t memory_used_delta = target_->GetUsage(handle);
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bool erased = target_->Release(handle, erase_if_last_ref);
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if (erased) {
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assert(cache_res_mgr_);
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cache_res_mgr_
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->UpdateCacheReservation(memory_used_delta, /* increase */ false)
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.PermitUncheckedError();
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}
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return erased;
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}
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void ChargedCache::Erase(const Slice& key) {
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target_->Erase(key);
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assert(cache_res_mgr_);
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cache_res_mgr_->UpdateCacheReservation(target_->GetUsage())
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.PermitUncheckedError();
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}
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void ChargedCache::EraseUnRefEntries() {
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target_->EraseUnRefEntries();
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assert(cache_res_mgr_);
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cache_res_mgr_->UpdateCacheReservation(target_->GetUsage())
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.PermitUncheckedError();
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}
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void ChargedCache::SetCapacity(size_t capacity) {
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target_->SetCapacity(capacity);
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// SetCapacity can result in evictions when the cache capacity is decreased,
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// so we would want to update the cache reservation here as well.
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assert(cache_res_mgr_);
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cache_res_mgr_->UpdateCacheReservation(target_->GetUsage())
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.PermitUncheckedError();
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}
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} // namespace ROCKSDB_NAMESPACE
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