The prefetching mechanism uses two classes (TFilePrefetch and TFPBlock) to prefetch in advance a block of tree entries.

There is a thread which takes care of actually transferring the blocks and making them available to the main requesting thread. Therefore, the time spent by the main thread waiting for the data before processing considerably decreases. Besides the prefetching mechanisms there is also a local caching option which can be enabled by the user. Both capabilities are disabled by default and must be explicitly enabled by the user.

Definition at line 51 of file TFilePrefetch.h.

Public Member Functions
	TFilePrefetch (TFile *)

virtual	~TFilePrefetch ()
	Destructor. More...

void	ReadAsync (TFPBlock *, Bool_t &)
	Read one block and insert it in prefetchBuffers list. More...

void	ReadListOfBlocks ()
	Get blocks specified in prefetchBlocks. More...

void	AddPendingBlock (TFPBlock *)
	Safe method to add a block to the pendingList. More...

TFPBlock *	GetPendingBlock ()
	Safe method to remove a block from the pendingList. More...

void	AddReadBlock (TFPBlock *)
	Safe method to add a block to the readList. More...

Bool_t	ReadBuffer (char *, Long64_t, Int_t)
	Return a prefetched element. More...

void	ReadBlock (Long64_t , Int_t , Int_t)
	Create a TFPBlock object or recycle one and add it to the prefetchBlocks list. More...

TFPBlock *	CreateBlockObj (Long64_t , Int_t , Int_t)
	Create a new block or recycle an old one. More...

TThread *	GetThread () const
	Return reference to the consumer thread. More...

Int_t	ThreadStart ()
	Used to start the consumer thread. More...

Bool_t	SetCache (const char *)
	Set the path of the cache directory. More...

Bool_t	CheckBlockInCache (char &, TFPBlock )
	Test if the block is in cache. More...

char *	GetBlockFromCache (const char *, Int_t)
	Return a buffer from cache. More...

void	SaveBlockInCache (TFPBlock *)
	Save the block content in cache. More...

Int_t	SumHex (const char *)
	Sum up individual hex values to obtain a decimal value. More...

Bool_t	BinarySearchReadList (TFPBlock , Long64_t, Int_t, Int_t )
	Search for a requested element in a block and return the index. More...

Long64_t	GetWaitTime ()
	Return the time spent wating for buffer to be read in microseconds. More...

void	SetFile (TFile *)
	Change the file. More...

std::condition_variable &	GetCondNewBlock ()

void	WaitFinishPrefetch ()
	Killing the async prefetching thread. More...

Bool_t	IsPrefetchFinished () const

	ClassDef (TFilePrefetch, 0)

Public Member Functions inherited from TObject
	TObject ()

	TObject (const TObject &object)
	TObject copy ctor. More...

TObject &	operator= (const TObject &rhs)
	TObject assignment operator. More...

virtual	~TObject ()
	TObject destructor. More...

virtual void	AppendPad (Option_t *option="")
	Append graphics object to current pad. More...

virtual void	Browse (TBrowser *b)
	Browse object. May be overridden for another default action. More...

virtual const char *	ClassName () const
	Returns name of class to which the object belongs. More...

virtual void	Clear (Option_t *="")

virtual TObject *	Clone (const char *newname="") const
	Make a clone of an object using the Streamer facility. More...

virtual Int_t	Compare (const TObject *obj) const
	Compare abstract method. More...

virtual void	Copy (TObject &object) const
	Copy this to obj. More...

virtual void	Delete (Option_t *option="")
	Delete this object. More...

virtual Int_t	DistancetoPrimitive (Int_t px, Int_t py)
	Computes distance from point (px,py) to the object. More...

virtual void	Draw (Option_t *option="")
	Default Draw method for all objects. More...

virtual void	DrawClass () const
	Draw class inheritance tree of the class to which this object belongs. More...

virtual TObject *	DrawClone (Option_t *option="") const
	Draw a clone of this object in the current pad. More...

virtual void	Dump () const
	Dump contents of object on stdout. More...

virtual void	Execute (const char method, const char params, Int_t *error=0)
	Execute method on this object with the given parameter string, e.g. More...

virtual void	Execute (TMethod method, TObjArray params, Int_t *error=0)
	Execute method on this object with parameters stored in the TObjArray. More...

virtual void	ExecuteEvent (Int_t event, Int_t px, Int_t py)
	Execute action corresponding to an event at (px,py). More...

virtual TObject *	FindObject (const char *name) const
	Must be redefined in derived classes. More...

virtual TObject *	FindObject (const TObject *obj) const
	Must be redefined in derived classes. More...

virtual Option_t *	GetDrawOption () const
	Get option used by the graphics system to draw this object. More...

virtual UInt_t	GetUniqueID () const
	Return the unique object id. More...

virtual const char *	GetName () const
	Returns name of object. More...

virtual const char *	GetIconName () const
	Returns mime type name of object. More...

virtual Option_t *	GetOption () const

virtual char *	GetObjectInfo (Int_t px, Int_t py) const
	Returns string containing info about the object at position (px,py). More...

virtual const char *	GetTitle () const
	Returns title of object. More...

virtual Bool_t	HandleTimer (TTimer *timer)
	Execute action in response of a timer timing out. More...

virtual ULong_t	Hash () const
	Return hash value for this object. More...

virtual Bool_t	InheritsFrom (const char *classname) const
	Returns kTRUE if object inherits from class "classname". More...

virtual Bool_t	InheritsFrom (const TClass *cl) const
	Returns kTRUE if object inherits from TClass cl. More...

virtual void	Inspect () const
	Dump contents of this object in a graphics canvas. More...

virtual Bool_t	IsFolder () const
	Returns kTRUE in case object contains browsable objects (like containers or lists of other objects). More...

virtual Bool_t	IsEqual (const TObject *obj) const
	Default equal comparison (objects are equal if they have the same address in memory). More...

virtual Bool_t	IsSortable () const

Bool_t	IsOnHeap () const

Bool_t	IsZombie () const

virtual Bool_t	Notify ()
	This method must be overridden to handle object notification. More...

virtual void	ls (Option_t *option="") const
	The ls function lists the contents of a class on stdout. More...

virtual void	Paint (Option_t *option="")
	This method must be overridden if a class wants to paint itself. More...

virtual void	Pop ()
	Pop on object drawn in a pad to the top of the display list. More...

virtual void	Print (Option_t *option="") const
	This method must be overridden when a class wants to print itself. More...

virtual Int_t	Read (const char *name)
	Read contents of object with specified name from the current directory. More...

virtual void	RecursiveRemove (TObject *obj)
	Recursively remove this object from a list. More...

virtual void	SaveAs (const char filename="", Option_t option="") const
	Save this object in the file specified by filename. More...

virtual void	SavePrimitive (std::ostream &out, Option_t *option="")
	Save a primitive as a C++ statement(s) on output stream "out". More...

virtual void	SetDrawOption (Option_t *option="")
	Set drawing option for object. More...

virtual void	SetUniqueID (UInt_t uid)
	Set the unique object id. More...

virtual void	UseCurrentStyle ()
	Set current style settings in this object This function is called when either TCanvas::UseCurrentStyle or TROOT::ForceStyle have been invoked. More...

virtual Int_t	Write (const char *name=0, Int_t option=0, Int_t bufsize=0)
	Write this object to the current directory. More...

virtual Int_t	Write (const char *name=0, Int_t option=0, Int_t bufsize=0) const
	Write this object to the current directory. More...

void *	operator new (size_t sz)

void *	operator new[] (size_t sz)

void *	operator new (size_t sz, void *vp)

void *	operator new[] (size_t sz, void *vp)

void	operator delete (void *ptr)
	Operator delete. More...

void	operator delete[] (void *ptr)
	Operator delete []. More...

void	SetBit (UInt_t f, Bool_t set)
	Set or unset the user status bits as specified in f. More...

void	SetBit (UInt_t f)

void	ResetBit (UInt_t f)

Bool_t	TestBit (UInt_t f) const

Int_t	TestBits (UInt_t f) const

void	InvertBit (UInt_t f)

virtual void	Info (const char method, const char msgfmt,...) const
	Issue info message. More...

virtual void	Warning (const char method, const char msgfmt,...) const
	Issue warning message. More...

virtual void	Error (const char method, const char msgfmt,...) const
	Issue error message. More...

virtual void	SysError (const char method, const char msgfmt,...) const
	Issue system error message. More...

virtual void	Fatal (const char method, const char msgfmt,...) const
	Issue fatal error message. More...

void	AbstractMethod (const char *method) const
	Use this method to implement an "abstract" method that you don't want to leave purely abstract. More...

void	MayNotUse (const char *method) const
	Use this method to signal that a method (defined in a base class) may not be called in a derived class (in principle against good design since a child class should not provide less functionality than its parent, however, sometimes it is necessary). More...

void	Obsolete (const char method, const char asOfVers, const char *removedFromVers) const
	Use this method to declare a method obsolete. More...

Static Private Member Functions
static TThread::VoidRtnFunc_t	ThreadProc (void *)
	Execution loop of the consumer thread. More...

Private Attributes
TFile *	fFile

TList *	fPendingBlocks

TList *	fReadBlocks

TThread *	fConsumer

std::mutex	fMutexPendingList

std::mutex	fMutexReadList

std::condition_variable	fNewBlockAdded

std::condition_variable	fReadBlockAdded

TSemaphore *	fSemChangeFile

TString	fPathCache

TStopwatch	fWaitTime

Bool_t	fThreadJoined

std::atomic< Bool_t >	fPrefetchFinished

Additional Inherited Members
Public Types inherited from TObject
enum	EStatusBits { kCanDelete = BIT(0), kMustCleanup = BIT(3), kObjInCanvas = BIT(3), kIsReferenced = BIT(4), kHasUUID = BIT(5), kCannotPick = BIT(6), kNoContextMenu = BIT(8), kInvalidObject = BIT(13) }

enum	{ kIsOnHeap = 0x01000000, kNotDeleted = 0x02000000, kZombie = 0x04000000, kBitMask = 0x00ffffff }

enum	{ kSingleKey = BIT(0), kOverwrite = BIT(1), kWriteDelete = BIT(2) }

Static Public Member Functions inherited from TObject
static Long_t	GetDtorOnly ()
	Return destructor only flag. More...

static void	SetDtorOnly (void *obj)
	Set destructor only flag. More...

static Bool_t	GetObjectStat ()
	Get status of object stat flag. More...

static void	SetObjectStat (Bool_t stat)
	Turn on/off tracking of objects in the TObjectTable. More...

Protected Member Functions inherited from TObject
void	MakeZombie ()

virtual void	DoError (int level, const char location, const char fmt, va_list va) const
	Interface to ErrorHandler (protected). More...

#include <TFilePrefetch.h>

Inheritance diagram for TFilePrefetch:

[legend]

Constructor & Destructor Documentation

TFilePrefetch::TFilePrefetch ( TFile * )

TFilePrefetch::~TFilePrefetch ( )

virtual

Destructor.

Definition at line 69 of file TFilePrefetch.cxx.

Member Function Documentation

void TFilePrefetch::AddPendingBlock ( TFPBlock * block )

Safe method to add a block to the pendingList.

Definition at line 220 of file TFilePrefetch.cxx.

void TFilePrefetch::AddReadBlock ( TFPBlock * block )

Safe method to add a block to the readList.

Definition at line 256 of file TFilePrefetch.cxx.

Bool_t TFilePrefetch::BinarySearchReadList	(	TFPBlock *	blockObj,
		Long64_t	offset,
		Int_t	len,
		Int_t *	index
	)

Search for a requested element in a block and return the index.

Definition at line 141 of file TFilePrefetch.cxx.

Bool_t TFilePrefetch::CheckBlockInCache	(	char *&	path,
		TFPBlock *	block
	)

Test if the block is in cache.

Definition at line 387 of file TFilePrefetch.cxx.

TFilePrefetch::ClassDef	(	TFilePrefetch	,
		0
	)

TFPBlock * TFilePrefetch::CreateBlockObj	(	Long64_t *	offset,
		Int_t *	len,
		Int_t	noblock
	)

Create a new block or recycle an old one.

Definition at line 278 of file TFilePrefetch.cxx.

char * TFilePrefetch::GetBlockFromCache	(	const char *	path,
		Int_t	length
	)

Return a buffer from cache.

Definition at line 433 of file TFilePrefetch.cxx.

std::condition_variable& TFilePrefetch::GetCondNewBlock ( )

inline

Definition at line 98 of file TFilePrefetch.h.

TFPBlock * TFilePrefetch::GetPendingBlock ( )

Safe method to remove a block from the pendingList.

Definition at line 232 of file TFilePrefetch.cxx.

TThread * TFilePrefetch::GetThread ( ) const

Return reference to the consumer thread.

Definition at line 300 of file TFilePrefetch.cxx.

Long64_t TFilePrefetch::GetWaitTime ( )

Return the time spent wating for buffer to be read in microseconds.

Definition at line 167 of file TFilePrefetch.cxx.

Referenced by TFileCacheRead::Print().

Bool_t TFilePrefetch::IsPrefetchFinished ( ) const

inline

Definition at line 100 of file TFilePrefetch.h.

Referenced by ThreadProc().

void TFilePrefetch::ReadAsync	(	TFPBlock *	block,
		Bool_t &	inCache
	)

Read one block and insert it in prefetchBuffers list.

Definition at line 103 of file TFilePrefetch.cxx.

void TFilePrefetch::ReadBlock	(	Long64_t *	offset,
		Int_t *	len,
		Int_t	nblock
	)

Create a TFPBlock object or recycle one and add it to the prefetchBlocks list.

Definition at line 211 of file TFilePrefetch.cxx.

Referenced by TFileCacheRead::ReadBufferExtPrefetch().

Bool_t TFilePrefetch::ReadBuffer	(	char *	buf,
		Long64_t	offset,
		Int_t	len
	)

Return a prefetched element.

Definition at line 175 of file TFilePrefetch.cxx.

Referenced by TFileCacheRead::ReadBufferExtPrefetch().

void TFilePrefetch::ReadListOfBlocks ( )

Get blocks specified in prefetchBlocks.

Definition at line 125 of file TFilePrefetch.cxx.

Referenced by ThreadProc().

void TFilePrefetch::SaveBlockInCache ( TFPBlock * block )

Save the block content in cache.

Definition at line 466 of file TFilePrefetch.cxx.

Bool_t TFilePrefetch::SetCache ( const char * path )

Set the path of the cache directory.

Definition at line 518 of file TFilePrefetch.cxx.

Referenced by TFileCacheRead::SetEnablePrefetchingImpl().

void TFilePrefetch::SetFile ( TFile * file )

Change the file.

When prefetching is enabled we also need to:

make sure the async thread is not doing any work
clear all blocks from prefetching and read list
reset the file pointer

Definition at line 314 of file TFilePrefetch.cxx.

Referenced by TFileCacheRead::SetFile().

Int_t TFilePrefetch::SumHex ( const char * hex )

Sum up individual hex values to obtain a decimal value.

Definition at line 373 of file TFilePrefetch.cxx.

TThread::VoidRtnFunc_t TFilePrefetch::ThreadProc ( void * arg )

staticprivate

Execution loop of the consumer thread.

Definition at line 357 of file TFilePrefetch.cxx.

Int_t TFilePrefetch::ThreadStart ( )

Used to start the consumer thread.

Definition at line 341 of file TFilePrefetch.cxx.

Referenced by TFileCacheRead::SetEnablePrefetchingImpl().

void TFilePrefetch::WaitFinishPrefetch ( )

Killing the async prefetching thread.

Definition at line 85 of file TFilePrefetch.cxx.

Referenced by TFileCacheRead::WaitFinishPrefetch().

Member Data Documentation

TThread* TFilePrefetch::fConsumer

private

Definition at line 57 of file TFilePrefetch.h.

TFile* TFilePrefetch::fFile

private

Definition at line 54 of file TFilePrefetch.h.

std::mutex TFilePrefetch::fMutexPendingList

private

Definition at line 58 of file TFilePrefetch.h.

std::mutex TFilePrefetch::fMutexReadList

private

Definition at line 59 of file TFilePrefetch.h.

std::condition_variable TFilePrefetch::fNewBlockAdded

private

Definition at line 60 of file TFilePrefetch.h.

Referenced by GetCondNewBlock().

TString TFilePrefetch::fPathCache

private

Definition at line 63 of file TFilePrefetch.h.

TList* TFilePrefetch::fPendingBlocks

private

Definition at line 55 of file TFilePrefetch.h.

std::atomic<Bool_t> TFilePrefetch::fPrefetchFinished

private

Definition at line 66 of file TFilePrefetch.h.

Referenced by IsPrefetchFinished().

std::condition_variable TFilePrefetch::fReadBlockAdded

private

Definition at line 61 of file TFilePrefetch.h.

TList* TFilePrefetch::fReadBlocks

private

Definition at line 56 of file TFilePrefetch.h.

TSemaphore* TFilePrefetch::fSemChangeFile

private

Definition at line 62 of file TFilePrefetch.h.

Bool_t TFilePrefetch::fThreadJoined

private

Definition at line 65 of file TFilePrefetch.h.

TStopwatch TFilePrefetch::fWaitTime

private

Definition at line 64 of file TFilePrefetch.h.

Collaboration diagram for TFilePrefetch:

[legend]

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

io/io/inc/TFilePrefetch.h
io/io/src/TFilePrefetch.cxx

Public Member Functions

Static Private Member Functions

Private Attributes

Additional Inherited Members

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation