139 lines
3.9 KiB
C++
139 lines
3.9 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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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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//
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#ifndef ROCKSDB_LITE
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#include "utilities/persistent_cache/volatile_tier_impl.h"
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#include <string>
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namespace rocksdb {
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void VolatileCacheTier::DeleteCacheData(VolatileCacheTier::CacheData* data) {
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assert(data);
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delete data;
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}
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VolatileCacheTier::~VolatileCacheTier() { index_.Clear(&DeleteCacheData); }
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PersistentCache::StatsType VolatileCacheTier::Stats() {
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std::map<std::string, double> stat;
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stat.insert({"persistent_cache.volatile_cache.hits",
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static_cast<double>(stats_.cache_hits_)});
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stat.insert({"persistent_cache.volatile_cache.misses",
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static_cast<double>(stats_.cache_misses_)});
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stat.insert({"persistent_cache.volatile_cache.inserts",
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static_cast<double>(stats_.cache_inserts_)});
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stat.insert({"persistent_cache.volatile_cache.evicts",
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static_cast<double>(stats_.cache_evicts_)});
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stat.insert({"persistent_cache.volatile_cache.hit_pct",
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static_cast<double>(stats_.CacheHitPct())});
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stat.insert({"persistent_cache.volatile_cache.miss_pct",
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static_cast<double>(stats_.CacheMissPct())});
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auto out = PersistentCacheTier::Stats();
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out.push_back(stat);
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return out;
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}
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Status VolatileCacheTier::Insert(const Slice& page_key, const char* data,
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const size_t size) {
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// precondition
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assert(data);
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assert(size);
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// increment the size
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size_ += size;
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// check if we have overshot the limit, if so evict some space
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while (size_ > max_size_) {
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if (!Evict()) {
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// unable to evict data, we give up so we don't spike read
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// latency
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assert(size_ >= size);
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size_ -= size;
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return Status::TryAgain("Unable to evict any data");
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}
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}
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assert(size_ >= size);
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// insert order: LRU, followed by index
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std::string key(page_key.data(), page_key.size());
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std::string value(data, size);
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std::unique_ptr<CacheData> cache_data(
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new CacheData(std::move(key), std::move(value)));
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bool ok = index_.Insert(cache_data.get());
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if (!ok) {
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// decrement the size that we incremented ahead of time
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assert(size_ >= size);
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size_ -= size;
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// failed to insert to cache, block already in cache
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return Status::TryAgain("key already exists in volatile cache");
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}
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cache_data.release();
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stats_.cache_inserts_++;
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return Status::OK();
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}
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Status VolatileCacheTier::Lookup(const Slice& page_key,
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std::unique_ptr<char[]>* result,
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size_t* size) {
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CacheData key(std::move(page_key.ToString()));
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CacheData* kv;
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bool ok = index_.Find(&key, &kv);
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if (ok) {
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// set return data
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result->reset(new char[kv->value.size()]);
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memcpy(result->get(), kv->value.c_str(), kv->value.size());
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*size = kv->value.size();
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// drop the reference on cache data
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kv->refs_--;
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// update stats
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stats_.cache_hits_++;
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return Status::OK();
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}
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stats_.cache_misses_++;
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if (next_tier()) {
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return next_tier()->Lookup(page_key, result, size);
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}
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return Status::NotFound("key not found in volatile cache");
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}
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bool VolatileCacheTier::Erase(const Slice& key) {
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assert(!"not supported");
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return true;
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}
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bool VolatileCacheTier::Evict() {
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CacheData* edata = index_.Evict();
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if (!edata) {
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// not able to evict any object
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return false;
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}
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stats_.cache_evicts_++;
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// push the evicted object to the next level
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if (next_tier()) {
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next_tier()->Insert(Slice(edata->key), edata->value.c_str(),
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edata->value.size());
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}
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// adjust size and destroy data
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size_ -= edata->value.size();
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delete edata;
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return true;
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}
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} // namespace rocksdb
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#endif
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