class AdaptiveLruPage

Bases: AdaptiveLruPageDynamicList, AdaptiveLruPageStaticList

One atomic piece that may be managed by a AdaptiveLru chain. To use this class, inherit from it and override evict_lru().

This class multiply inherits from two classes which in turn both inherit from LinkedListNode. This is just a sneaky C++ trick to allow this class to inherit from LinkedListNode twice, so that pages can be stored on two different linked lists simultaneously. The AdaptiveLru class depends on this; it maintains its pages in two different lists, one grouped by priority, and one in order by next partial update needs.

Inheritance diagram

explicit AdaptiveLruPage(std::size_t lru_size)
AdaptiveLruPage(AdaptiveLruPage const &copy)
void dequeue_lru(void)

Removes the page from its AdaptiveLru.

void enqueue_lru(AdaptiveLru *lru)

Adds the page to the LRU for the first time, or marks it recently-accessed if it has already been added.

If lru is NULL, it means to remove this page from its LRU.

virtual void evict_lru(void)

Evicts the page from the LRU. Called internally when the LRU determines that it is full. May also be called externally when necessary to explicitly evict the page.

It is legal for this method to either evict the page as requested, do nothing (in which case the eviction will be requested again at the next epoch), or requeue itself on the tail of the queue (in which case the eviction will be requested again much later).

AdaptiveLru *get_lru(void) const

Returns the LRU that manages this page, or NULL if it is not currently managed by any LRU.

std::size_t get_lru_size(void) const

Returns the size of this page as reported to the LRU, presumably in bytes.

unsigned int get_num_frames(void) const

Not defined in SimpleLruPage.

Returns the number of frames since the page was first added to its LRU. Returns 0 if it does not have an LRU.

unsigned int get_num_inactive_frames(void) const

Returns the number of frames since the page was last accessed on its LRU. Returns 0 if it does not have an LRU.

void mark_used_lru(void) const
void mark_used_lru(AdaptiveLru *lru)

To be called when the page is used; this will move it to the tail of the AdaptiveLru queue it is already on.

This method is const because it’s not technically modifying the contents of the page itself.

To be called when the page is used; this will move it to the tail of the specified AdaptiveLru queue.

virtual void output(std::ostream &out) const
void set_lru_size(std::size_t lru_size)

Specifies the size of this page, presumably in bytes, although any unit is possible.

virtual void write(std::ostream &out, int indent_level) const