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8a1a529fcc
Summary: Chad first noted that deserializing trees from the local store can be expensive. From the thrift side EdenFS does not have a copy of trees in memory. This means for glob files each of the trees that have not been materialized will be read from the local store. Since reading an deserializing trees from the local store can be expensive lets add an in memory cache so that some of these reads can be satisfied from here instead. Here we actually start to use the cache! Reviewed By: chadaustin Differential Revision: D27050310 fbshipit-source-id: e35db193fea0af7f387b6f44c49b5bcc2a902858
72 lines
2.2 KiB
C++
72 lines
2.2 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This software may be used and distributed according to the terms of the
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* GNU General Public License version 2.
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*/
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#pragma once
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#include "eden/fs/config/ReloadableConfig.h"
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#include "eden/fs/model/Tree.h"
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#include "eden/fs/store/ObjectCache.h"
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namespace facebook {
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namespace eden {
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class Hash;
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/**
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* An in-memory LRU cache for loaded trees. Currently, this will not be used by
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* the inode code as inodes store the tree data in the inode itself. This is
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* instead used from the thrift side to speed up glob evvaluation.
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*
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* It is parameterized by both a maximum cache size and a minimum entry count.
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* The cache tries to evict entries when the total number of loaded trees
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* exceeds the maximum cache size, except that it always keeps the minimum
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* entry count around.
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*
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* The intent of the minimum entry count is to avoid having to reload
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* frequently-accessed large trees when they are larger than the maximum cache
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* size. Note that if you want trees larger than the maximum size in bytes to
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* be cachable your minimum entry count must be atleast 1, otherwise insert may
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* not actually insert the tree into the cache.
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*
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* It is safe to use this object from arbitrary threads.
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*/
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class TreeCache : public ObjectCache<Tree, ObjectCacheFlavor::Simple> {
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public:
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static std::shared_ptr<TreeCache> create(
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std::shared_ptr<ReloadableConfig> config) {
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struct TC : TreeCache {
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explicit TC(std::shared_ptr<ReloadableConfig> c) : TreeCache{c} {}
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};
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return std::make_shared<TC>(config);
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}
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~TreeCache() = default;
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/**
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* If a tree for the given hash is in cache, return it. If the tree is not in
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* cache, return nullptr.
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*/
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std::shared_ptr<const Tree> get(const Hash& hash);
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/**
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* Inserts a tree into the cache for future lookup. If the new total size
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* exceeds the maximum cache size and the minimum entry count, old entries are
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* evicted.
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*/
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void insert(std::shared_ptr<const Tree> tree);
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private:
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/**
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* Reference to the eden config, may be a null pointer in unit tests.
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*/
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std::shared_ptr<ReloadableConfig> config_;
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explicit TreeCache(std::shared_ptr<ReloadableConfig> config);
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};
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} // namespace eden
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} // namespace facebook
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