#include <TStorageFactoryFile.h>

Inheritance diagram for TStorageFactoryFile:

Public Member Functions
	ClassDef (TStorageFactoryFile, 0)

virtual Bool_t	ReadBuffer (char *buf, Int_t len)

virtual Bool_t	ReadBuffer (char *buf, Long64_t pos, Int_t len)

virtual Bool_t	ReadBufferAsync (Long64_t off, Int_t len)

virtual Bool_t	ReadBuffers (char buf, Long64_t pos, Int_t *len, Int_t nbuf)

void	ResetErrno (void) const

	TStorageFactoryFile (const char name, Option_t option, const char *ftitle, Int_t compress, Int_t netopt, Bool_t parallelopen=kFALSE)

	TStorageFactoryFile (const char name, Option_t option="", const char *ftitle="", Int_t compress=1)

virtual Bool_t	WriteBuffer (const char *buf, Int_t len)

	~TStorageFactoryFile (void)

Protected Member Functions
virtual Int_t	SysClose (Int_t fd)

virtual Int_t	SysOpen (const char *pathname, Int_t flags, UInt_t mode)

virtual Long64_t	SysSeek (Int_t fd, Long64_t offset, Int_t whence)

virtual Int_t	SysStat (Int_t fd, Long_t id, Long64_t size, Long_t flags, Long_t modtime)

virtual Int_t	SysSync (Int_t fd)

Private Member Functions
void	Initialize (const char name, Option_t option="")

Bool_t	ReadBuffersSync (char buf, Long64_t pos, Int_t *len, Int_t nbuf)

void	releaseStorage ()

	TStorageFactoryFile (void)

Private Attributes
edm::propagate_const < std::unique_ptr< Storage > >	storage_

Detailed Description

TFile wrapper around StorageFactory and Storage.

Definition at line 16 of file TStorageFactoryFile.h.

Constructor & Destructor Documentation

TStorageFactoryFile::TStorageFactoryFile	(	const char *	name,
		Option_t *	option,
		const char *	ftitle,
		Int_t	compress,
		Int_t	netopt,
		Bool_t	parallelopen = `kFALSE`
	)

Definition at line 108 of file TStorageFactoryFile.cc.

TStorageFactoryFile::TStorageFactoryFile	(	const char *	name,
		Option_t *	option = `""`,
		const char *	ftitle = `""`,
		Int_t	compress = `1`
	)

Definition at line 124 of file TStorageFactoryFile.cc.

TStorageFactoryFile::~TStorageFactoryFile ( void )

Definition at line 225 of file TStorageFactoryFile.cc.

TStorageFactoryFile::TStorageFactoryFile ( void )

private

Definition at line 97 of file TStorageFactoryFile.cc.

Member Function Documentation

TStorageFactoryFile::ClassDef	(	TStorageFactoryFile	,
		0
	)

void TStorageFactoryFile::Initialize	(	const char *	name,
		Option_t *	option = `""`
	)

private

Definition at line 139 of file TStorageFactoryFile.cc.

Bool_t TStorageFactoryFile::ReadBuffer	(	char *	buf,
		Int_t	len
	)

virtual

Definition at line 244 of file TStorageFactoryFile.cc.

Bool_t TStorageFactoryFile::ReadBuffer	(	char *	buf,
		Long64_t	pos,
		Int_t	len
	)

virtual

Definition at line 235 of file TStorageFactoryFile.cc.

Bool_t TStorageFactoryFile::ReadBufferAsync	(	Long64_t	off,
		Int_t	len
	)

virtual

Definition at line 311 of file TStorageFactoryFile.cc.

Bool_t TStorageFactoryFile::ReadBuffers	(	char *	buf,
		Long64_t *	pos,
		Int_t *	len,
		Int_t	nbuf
	)

virtual

Definition at line 432 of file TStorageFactoryFile.cc.

Bool_t TStorageFactoryFile::ReadBuffersSync	(	char *	buf,
		Long64_t *	pos,
		Int_t *	len,
		Int_t	nbuf
	)

private

Most storage systems are not prepared for the onslaught of small reads that ROOT will perform, even if they implement a vectored read interface.

Typically, on the server side, the loop is unrolled and the reads are issued sequentially - giving the OS no hint that you're about to read a very close-by byte in the near future. Normally, OS read-ahead takes care of such situations; because the storage server has so many clients, and ROOT reads look random to the OS, the read-ahead becomes disabled.

Hence, this function will repack the application-layer request into an optimized storage-layer request. The resulting request to the storage layer typically has a slightly larger number of bytes, but far less individual reads.

On average, the server's disks see a smaller number of overall reads, the number of bytes transferred over the network increases modestly (around 10%), and the single application request becomes one-to-two I/O transactions. A clear win for all cases except high-latency WAN.

Definition at line 365 of file TStorageFactoryFile.cc.

void TStorageFactoryFile::releaseStorage ( )

inlineprivate

Definition at line 56 of file TStorageFactoryFile.h.

References edm::get_underlying_safe(), and storage_.

56 {get_underlying_safe(storage_).release();}

TStorageFactoryFile::storage_

edm::propagate_const< std::unique_ptr< Storage > > storage_

Definition: TStorageFactoryFile.h:60

edm::get_underlying_safe

std::shared_ptr< T > & get_underlying_safe(propagate_const< std::shared_ptr< T >> &iP)

Definition: get_underlying_safe.h:41