mongo::RecordAccessTracker Class Reference

Used to implement likelyInPhysicalMemory() for the MMAP v1 storage engine. More...

#include <record_access_tracker.h>

Detailed Description

Used to implement likelyInPhysicalMemory() for the MMAP v1 storage engine.

Since MMAP v1 holds exclusive collection-level locks, it should yield the locks during a page fault. The RecordAccessTracker is used to guess at which records are in memory, so that a yield can be requested unless we're sure that the record has been recently accessed.

Classes
struct	Entry
class	Rolling
	this contains many slices of times the idea you put mem status in the current time slice and then after a certain period of time, it rolls off so we check again More...
class	Slice
	simple hash map for region -> status this constitutes a single region of time it does chaining, but very short chains More...

Public Types
enum	Constants {   SliceSize = 1024, MaxChain = 20, NumSlices = 10, RotateTimeSecs = 90,   BigHashSize = 128 }

Public Member Functions
	RecordAccessTracker (ClockSource *cs)
void	markAccessed (const void *record)
	Informs this record access tracker that 'record' has been accessed. More...
bool	checkAccessedAndMark (const void *record)
void	reset ()
	Clears out any history of record accesses. More...
void	disableSystemBlockInMemCheck ()
	The accessedRecently() implementation falls back to making a system call if it appears that the record is not in physical memory. More...

Private Types
enum	State { In, Out, Unk }

Private Member Functions
	MONGO_DISALLOW_COPYING (RecordAccessTracker)

Private Attributes
bool	_blockSupported
ClockSource *	_clock
std::unique_ptr< Rolling[]>	_rollingTable

Member Enumeration Documentation

Constants

enum mongo::RecordAccessTracker::Constants

Enumerator
SliceSize
MaxChain
NumSlices
RotateTimeSecs
BigHashSize

State

enum mongo::RecordAccessTracker::State

private

Enumerator
In
Out
Unk

Constructor & Destructor Documentation

RecordAccessTracker()

mongo::RecordAccessTracker::RecordAccessTracker

(

ClockSource *

cs

)

Member Function Documentation

checkAccessedAndMark()

bool mongo::RecordAccessTracker::checkAccessedAndMark

(

const void *

record

)

Returns

whether or not 'record' has been marked as accessed recently. A return value of true means that 'record' is likely in physical memory.

Also has the side effect of marking 'record' as accessed.

disableSystemBlockInMemCheck()

void mongo::RecordAccessTracker::disableSystemBlockInMemCheck

(

)

The accessedRecently() implementation falls back to making a system call if it appears that the record is not in physical memory.

Use this method to disable the fallback for testing.

markAccessed()

void mongo::RecordAccessTracker::markAccessed

(

const void *

record

)

Informs this record access tracker that 'record' has been accessed.

MONGO_DISALLOW_COPYING()

mongo::RecordAccessTracker::MONGO_DISALLOW_COPYING ( RecordAccessTracker  )

private

reset()

void mongo::RecordAccessTracker::reset

(

)

Clears out any history of record accesses.

Member Data Documentation

_blockSupported

bool mongo::RecordAccessTracker::_blockSupported

private

_clock

ClockSource* mongo::RecordAccessTracker::_clock

private

_rollingTable

std::unique_ptr<Rolling[]> mongo::RecordAccessTracker::_rollingTable

private

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The documentation for this class was generated from the following files:

• /home/louis/git/mongodbsource.github.io/src/src/mongo/db/storage/mmap_v1/record_access_tracker.h
• /home/louis/git/mongodbsource.github.io/src/src/mongo/db/storage/mmap_v1/record_access_tracker.cpp