Snapshot Cache Manager

Snapshot Cache Manager, which caches data pages retrieved from snapshot files. More...

Detailed Description

Snapshot Cache Manager, which caches data pages retrieved from snapshot files.

Overview

Snapshot Cache is a node-local read-only cache of snapshot pages. In some sense, it is a special kind of bufferpool that is much simpler and faster than traditional implementations due to the special requirements; no modifications, no interaction with logging module nor commit protocol, no guarantee needed for uniqueness (no problem to occasionally have two cached instances of the same page; just a bit waste of space). The operation to retrieve a snapshot page, especially when the page is in this cache, must be VERY fast. Thus, this cache manager must be highly optimized for read operations.

Structure

For each NUMA node memory, we have a hashtable structure whose key is snapshot-id/page-id and whose value is offset in cache memory.

Collaboration diagram for Snapshot Cache Manager:

Files
file	fwd.hpp
	Forward declarations of classes in cache package.

Classes
struct	foedus::cache::HashFunc
	A simple hash function logic used in snasphot cache. More...
struct	foedus::cache::CacheHashtable::EvictArgs
	Parameters for evict() More...
struct	foedus::cache::CacheHashtable::Stat
class	foedus::cache::CacheHashtable
	A NUMA-local hashtable of cached snapshot pages. More...
class	foedus::cache::CacheManager
	Snapshot cache manager. More...
class	foedus::cache::CacheManagerPimpl
	Pimpl object of CacheManager. More...
struct	foedus::cache::CacheOptions
	Set of options for snapshot cache manager. More...
class	foedus::cache::SnapshotFileSet
	Holds a set of read-only file objects for snapshot files. More...

---

Class Documentation

struct foedus::cache::CacheHashtable::Stat

Definition at line 328 of file cache_hashtable.hpp.

Class Members
uint32_t	normal_entries_
uint32_t	overflow_entries_