Logo ROOT   6.19/01
Reference Guide
TFilePrefetch Class Reference


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 31 of file TFilePrefetch.h.

Public Member Functions

 TFilePrefetch (TFile *)
 Constructor. More...
 
virtual ~TFilePrefetch ()
 Destructor. More...
 
void AddPendingBlock (TFPBlock *)
 Safe method to add a block to the pendingList. More...
 
void AddReadBlock (TFPBlock *)
 Safe method to add a block to the readList. More...
 
Bool_t BinarySearchReadList (TFPBlock *, Long64_t, Int_t, Int_t *)
 Search for a requested element in a block and return the index. More...
 
Bool_t CheckBlockInCache (char *&, TFPBlock *)
 Test if the block is in cache. More...
 
TFPBlockCreateBlockObj (Long64_t *, Int_t *, Int_t)
 Create a new block or recycle an old one. More...
 
char * GetBlockFromCache (const char *, Int_t)
 Return a buffer from cache. More...
 
std::condition_variable & GetCondNewBlock ()
 
TFPBlockGetPendingBlock ()
 Safe method to remove a block from the pendingList. More...
 
TThreadGetThread () const
 Return reference to the consumer thread. More...
 
Long64_t GetWaitTime ()
 Return the time spent wating for buffer to be read in microseconds. More...
 
Bool_t IsPrefetchFinished () const
 
void ReadAsync (TFPBlock *, Bool_t &)
 Read one block and insert it in prefetchBuffers list. More...
 
void ReadBlock (Long64_t *, Int_t *, Int_t)
 Create a TFPBlock object or recycle one and add it to the prefetchBlocks list. More...
 
Bool_t ReadBuffer (char *, Long64_t, Int_t)
 Return a prefetched element. More...
 
void ReadListOfBlocks ()
 Get blocks specified in prefetchBlocks. More...
 
void SaveBlockInCache (TFPBlock *)
 Save the block content in cache. More...
 
Bool_t SetCache (const char *)
 Set the path of the cache directory. More...
 
void SetFile (TFile *file, TFile::ECacheAction action=TFile::kDisconnect)
 Change the file. More...
 
Int_t SumHex (const char *)
 Sum up individual hex values to obtain a decimal value. More...
 
Int_t ThreadStart ()
 Used to start the consumer thread. More...
 
void WaitFinishPrefetch ()
 Killing the async prefetching thread. More...
 
- Public Member Functions inherited from TObject
 TObject ()
 TObject constructor. More...
 
 TObject (const TObject &object)
 TObject copy ctor. More...
 
virtual ~TObject ()
 TObject destructor. 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...
 
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...
 
ULong_t CheckedHash ()
 Check and record whether this class has a consistent Hash/RecursiveRemove setup (*) and then return the regular Hash value for this object. More...
 
virtual const char * ClassName () const
 Returns name of class to which the object belongs. More...
 
virtual void Clear (Option_t *="")
 
virtual TObjectClone (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 TObjectDrawClone (Option_t *option="") const
 Draw a clone of this object in the current selected pad for instance with: gROOT->SetSelectedPad(gPad). More...
 
virtual void Dump () const
 Dump contents of object on stdout. More...
 
virtual void Error (const char *method, const char *msgfmt,...) const
 Issue error message. 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 void Fatal (const char *method, const char *msgfmt,...) const
 Issue fatal error message. More...
 
virtual TObjectFindObject (const char *name) const
 Must be redefined in derived classes. More...
 
virtual TObjectFindObject (const TObject *obj) const
 Must be redefined in derived classes. More...
 
virtual Option_tGetDrawOption () const
 Get option used by the graphics system to draw this object. More...
 
virtual const char * GetIconName () const
 Returns mime type name of object. More...
 
virtual const char * GetName () const
 Returns name of object. More...
 
virtual char * GetObjectInfo (Int_t px, Int_t py) const
 Returns string containing info about the object at position (px,py). More...
 
virtual Option_tGetOption () const
 
virtual const char * GetTitle () const
 Returns title of object. More...
 
virtual UInt_t GetUniqueID () const
 Return the unique object id. 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...
 
Bool_t HasInconsistentHash () const
 Return true is the type of this object is known to have an inconsistent setup for Hash and RecursiveRemove (i.e. More...
 
virtual void Info (const char *method, const char *msgfmt,...) const
 Issue info message. 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...
 
void InvertBit (UInt_t f)
 
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 IsFolder () const
 Returns kTRUE in case object contains browsable objects (like containers or lists of other objects). More...
 
R__ALWAYS_INLINE Bool_t IsOnHeap () const
 
virtual Bool_t IsSortable () const
 
R__ALWAYS_INLINE Bool_t IsZombie () const
 
virtual void ls (Option_t *option="") const
 The ls function lists the contents of a class on stdout. 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...
 
virtual Bool_t Notify ()
 This method must be overridden to handle object notification. More...
 
void Obsolete (const char *method, const char *asOfVers, const char *removedFromVers) const
 Use this method to declare a method obsolete. More...
 
void operator delete (void *ptr)
 Operator delete. More...
 
void operator delete[] (void *ptr)
 Operator delete []. More...
 
voidoperator new (size_t sz)
 
voidoperator new (size_t sz, void *vp)
 
voidoperator new[] (size_t sz)
 
voidoperator new[] (size_t sz, void *vp)
 
TObjectoperator= (const TObject &rhs)
 TObject assignment operator. 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...
 
void ResetBit (UInt_t f)
 
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...
 
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)
 
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 SysError (const char *method, const char *msgfmt,...) const
 Issue system error message. More...
 
R__ALWAYS_INLINE Bool_t TestBit (UInt_t f) const
 
Int_t TestBits (UInt_t f) const
 
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 void Warning (const char *method, const char *msgfmt,...) const
 Issue warning message. 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...
 

Static Private Member Functions

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

Private Attributes

TThreadfConsumer
 
TFilefFile
 
std::mutex fMutexPendingList
 
std::mutex fMutexReadList
 
std::condition_variable fNewBlockAdded
 
TString fPathCache
 
TListfPendingBlocks
 
std::atomic< Bool_tfPrefetchFinished
 
std::condition_variable fReadBlockAdded
 
TListfReadBlocks
 
TSemaphorefSemChangeFile
 
Bool_t fThreadJoined
 
TStopwatch fWaitTime
 

Additional Inherited Members

- Public Types inherited from TObject
enum  {
  kIsOnHeap = 0x01000000, kNotDeleted = 0x02000000, kZombie = 0x04000000, kInconsistent = 0x08000000,
  kBitMask = 0x00ffffff
}
 
enum  { kSingleKey = BIT(0), kOverwrite = BIT(1), kWriteDelete = BIT(2) }
 
enum  EDeprecatedStatusBits { kObjInCanvas = BIT(3) }
 
enum  EStatusBits {
  kCanDelete = BIT(0), kMustCleanup = BIT(3), kIsReferenced = BIT(4), kHasUUID = BIT(5),
  kCannotPick = BIT(6), kNoContextMenu = BIT(8), kInvalidObject = BIT(13)
}
 
- Static Public Member Functions inherited from TObject
static Long_t GetDtorOnly ()
 Return destructor only flag. More...
 
static Bool_t GetObjectStat ()
 Get status of object stat flag. More...
 
static void SetDtorOnly (void *obj)
 Set destructor only flag. More...
 
static void SetObjectStat (Bool_t stat)
 Turn on/off tracking of objects in the TObjectTable. More...
 
- Protected Member Functions inherited from TObject
virtual void DoError (int level, const char *location, const char *fmt, va_list va) const
 Interface to ErrorHandler (protected). More...
 
void MakeZombie ()
 

#include <TFilePrefetch.h>

Inheritance diagram for TFilePrefetch:
[legend]

Constructor & Destructor Documentation

◆ TFilePrefetch()

TFilePrefetch::TFilePrefetch ( TFile file)

Constructor.

Definition at line 52 of file TFilePrefetch.cxx.

◆ ~TFilePrefetch()

TFilePrefetch::~TFilePrefetch ( )
virtual

Destructor.

Definition at line 70 of file TFilePrefetch.cxx.

Member Function Documentation

◆ AddPendingBlock()

void TFilePrefetch::AddPendingBlock ( TFPBlock block)

Safe method to add a block to the pendingList.

Definition at line 221 of file TFilePrefetch.cxx.

◆ AddReadBlock()

void TFilePrefetch::AddReadBlock ( TFPBlock block)

Safe method to add a block to the readList.

Definition at line 257 of file TFilePrefetch.cxx.

◆ BinarySearchReadList()

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 142 of file TFilePrefetch.cxx.

◆ CheckBlockInCache()

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

Test if the block is in cache.

Definition at line 393 of file TFilePrefetch.cxx.

◆ CreateBlockObj()

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

Create a new block or recycle an old one.

Definition at line 279 of file TFilePrefetch.cxx.

◆ GetBlockFromCache()

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

Return a buffer from cache.

Definition at line 439 of file TFilePrefetch.cxx.

◆ GetCondNewBlock()

std::condition_variable& TFilePrefetch::GetCondNewBlock ( )
inline

Definition at line 78 of file TFilePrefetch.h.

◆ GetPendingBlock()

TFPBlock * TFilePrefetch::GetPendingBlock ( )

Safe method to remove a block from the pendingList.

Definition at line 233 of file TFilePrefetch.cxx.

◆ GetThread()

TThread * TFilePrefetch::GetThread ( ) const

Return reference to the consumer thread.

Definition at line 301 of file TFilePrefetch.cxx.

◆ GetWaitTime()

Long64_t TFilePrefetch::GetWaitTime ( )

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

Definition at line 168 of file TFilePrefetch.cxx.

◆ IsPrefetchFinished()

Bool_t TFilePrefetch::IsPrefetchFinished ( ) const
inline

Definition at line 80 of file TFilePrefetch.h.

◆ ReadAsync()

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

Read one block and insert it in prefetchBuffers list.

Definition at line 104 of file TFilePrefetch.cxx.

◆ ReadBlock()

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 212 of file TFilePrefetch.cxx.

◆ ReadBuffer()

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

Return a prefetched element.

Definition at line 176 of file TFilePrefetch.cxx.

◆ ReadListOfBlocks()

void TFilePrefetch::ReadListOfBlocks ( )

Get blocks specified in prefetchBlocks.

Definition at line 126 of file TFilePrefetch.cxx.

◆ SaveBlockInCache()

void TFilePrefetch::SaveBlockInCache ( TFPBlock block)

Save the block content in cache.

Definition at line 472 of file TFilePrefetch.cxx.

◆ SetCache()

Bool_t TFilePrefetch::SetCache ( const char *  path)

Set the path of the cache directory.

Definition at line 524 of file TFilePrefetch.cxx.

◆ SetFile()

void TFilePrefetch::SetFile ( TFile file,
TFile::ECacheAction  action = TFile::kDisconnect 
)

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 315 of file TFilePrefetch.cxx.

◆ SumHex()

Int_t TFilePrefetch::SumHex ( const char *  hex)

Sum up individual hex values to obtain a decimal value.

Definition at line 379 of file TFilePrefetch.cxx.

◆ ThreadProc()

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

Execution loop of the consumer thread.

Definition at line 363 of file TFilePrefetch.cxx.

◆ ThreadStart()

Int_t TFilePrefetch::ThreadStart ( )

Used to start the consumer thread.

Definition at line 347 of file TFilePrefetch.cxx.

◆ WaitFinishPrefetch()

void TFilePrefetch::WaitFinishPrefetch ( )

Killing the async prefetching thread.

Definition at line 86 of file TFilePrefetch.cxx.

Member Data Documentation

◆ fConsumer

TThread* TFilePrefetch::fConsumer
private

Definition at line 37 of file TFilePrefetch.h.

◆ fFile

TFile* TFilePrefetch::fFile
private

Definition at line 34 of file TFilePrefetch.h.

◆ fMutexPendingList

std::mutex TFilePrefetch::fMutexPendingList
private

Definition at line 38 of file TFilePrefetch.h.

◆ fMutexReadList

std::mutex TFilePrefetch::fMutexReadList
private

Definition at line 39 of file TFilePrefetch.h.

◆ fNewBlockAdded

std::condition_variable TFilePrefetch::fNewBlockAdded
private

Definition at line 40 of file TFilePrefetch.h.

◆ fPathCache

TString TFilePrefetch::fPathCache
private

Definition at line 43 of file TFilePrefetch.h.

◆ fPendingBlocks

TList* TFilePrefetch::fPendingBlocks
private

Definition at line 35 of file TFilePrefetch.h.

◆ fPrefetchFinished

std::atomic<Bool_t> TFilePrefetch::fPrefetchFinished
private

Definition at line 46 of file TFilePrefetch.h.

◆ fReadBlockAdded

std::condition_variable TFilePrefetch::fReadBlockAdded
private

Definition at line 41 of file TFilePrefetch.h.

◆ fReadBlocks

TList* TFilePrefetch::fReadBlocks
private

Definition at line 36 of file TFilePrefetch.h.

◆ fSemChangeFile

TSemaphore* TFilePrefetch::fSemChangeFile
private

Definition at line 42 of file TFilePrefetch.h.

◆ fThreadJoined

Bool_t TFilePrefetch::fThreadJoined
private

Definition at line 45 of file TFilePrefetch.h.

◆ fWaitTime

TStopwatch TFilePrefetch::fWaitTime
private

Definition at line 44 of file TFilePrefetch.h.

Libraries for TFilePrefetch:
[legend]

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