#include <cstdint>
#include <memory>
#include <vector>
#include "mem/cache/replacement_policies/base.hh"

Classes
class	TreePLRURP

struct	TreePLRURP::TreePLRUReplData
	Tree-PLRU-specific implementation of replacement data. More...

Detailed Description

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Declaration of a Pseudo-Least Recently Used replacement policy. The victim is chosen using a tree of bit timestamps.

A tree contains consists of leafs that represent the direction to take when searching for the LRU entry.

Let's assume each tree contains 8 replacement data entries. For example, if these entries are named from A to H, and the tree's bits are: ____1____ 0 1 0 1 1 0 A B C D E F G H

Then the current PLRU entry is given by the sequence: 1 (get right child) -> 1 (get right child) -> 0 (get left child) -> G

When an entry is touched the bits of the parent nodes are iteratively updated to point away from it. Therefore, if entry B is touched, its parent, grandparents, etc would be updated, and we'd end up with the following tree: ____1____ 1 1 0 1 1 0 A B C D E F G H

Explanation: The parent of B must point away from it, that is, to the left child, but it is already doing so, so it is left unmodified (0). Then the grandparent must point to the right subtree, as B belongs to its left subtree (0 becomes 1). Lastly, the root must point away from the grandparent, so it is left unmodified (0).

For invalidations the process is similar to touches, but instead of pointing away, the bits point toward the entry.

Consecutive calls to instantiateEntry() use the same tree up to numLeaves. When numLeaves replacement datas have been created, a new tree is generated, and the counter is reset.

Definition in file tree_plru_rp.hh.

Classes

Detailed Description