TDEZoneAllocator Class Reference

#include <kallocator.h>

Public Member Functions
	TDEZoneAllocator (unsigned long _blockSize=8 *1024)
	~TDEZoneAllocator ()
void *	allocate (size_t _size)
void	deallocate (void *ptr)
void	free_since (void *ptr)

Protected Types
typedef TQValueList< MemBlock * >	MemList

Protected Member Functions
void	addBlock (MemBlock *b)
void	delBlock (MemBlock *b)
void	insertHash (MemBlock *b)
void	initHash ()

Protected Attributes
MemBlock *	currentBlock
unsigned long	blockSize
unsigned long	blockOffset
unsigned int	log2
unsigned int	num_blocks
MemList **	hashList
unsigned int	hashSize
bool	hashDirty

Detailed Description

Memory allocator for large groups of small objects.

This should be used for large groups of objects that are created and destroyed together. When used carefully for this purpose it is faster and more memory efficient than malloc. Additionally to a usual obstack like allocator you can also free the objects individually. Because it does no compaction it still is faster then malloc()/free(). Depending on the exact usage pattern that might come at the expense of some memory though.

Author

Waldo Bastian basti.nosp@m.an@k.nosp@m.de.or.nosp@m.g, Michael Matz matz@.nosp@m.kde..nosp@m.org

Definition at line 46 of file kallocator.h.

Member Typedef Documentation

MemList

typedef TQValueList<MemBlock *> TDEZoneAllocator::MemList

protected

A list of chunks.

Definition at line 115 of file kallocator.h.

Constructor & Destructor Documentation

TDEZoneAllocator()

TDEZoneAllocator::TDEZoneAllocator

(

unsigned long

_blockSize = 8*1024

)

Creates a TDEZoneAllocator object.

Parameters

_blockSize

Size in bytes of the blocks requested from malloc.

Definition at line 48 of file kallocator.cpp.

~TDEZoneAllocator()

TDEZoneAllocator::~TDEZoneAllocator

(

)

Destructs the ZoneAllocator and free all memory allocated by it.

Definition at line 59 of file kallocator.cpp.

Member Function Documentation

addBlock()

void TDEZoneAllocator::addBlock ( MemBlock *  b )

protected

Add a new memory block to the pool of blocks, and reorganize the hash lists if needed.

Parameters

b	block to add

Definition at line 102 of file kallocator.cpp.

allocate()

void * TDEZoneAllocator::allocate

(

size_t

_size

)

Allocates a memory block.

Parameters

_size

Size in bytes of the memory block. Memory is aligned to the size of a pointer.

Definition at line 184 of file kallocator.cpp.

deallocate()

void TDEZoneAllocator::deallocate

(

void *

ptr

)

Gives back a block returned by allocate() to the zone allocator, and possibly deallocates the block holding it (when it's empty).

The first deallocate() after many allocate() calls (or the first at all) builds an internal data structure for speeding up deallocation. The consistency of that structure is maintained from then on (by allocate() and deallocate()) unless many more objects are allocated without any intervening deallocation, in which case it's thrown away and rebuilt at the next deallocate().

The effect of this is, that such initial deallocate() calls take more time then the normal calls, and that after this list is built, i.e. generally if deallocate() is used at all, also allocate() is a little bit slower. This means, that if you want to squeeze out the last bit performance you would want to use TDEZoneAllocator as an obstack, i.e. just use the functions allocate() and free_since(). All the remaining memory is returned to the system if the zone allocator is destroyed.

Parameters

ptr	Pointer as returned by allocate().

Definition at line 207 of file kallocator.cpp.

delBlock()

void TDEZoneAllocator::delBlock ( MemBlock *  b )

protected

Delete a memory block.

This really returns the memory to the heap.

Parameters

b	block to delete

Definition at line 148 of file kallocator.cpp.

free_since()

void TDEZoneAllocator::free_since

(

void *

ptr

)

Deallocate many objects at once.

free_since() deallocates all objects allocated after ptr, including ptr itself.

The intended use is something along the lines of:

TDEZoneAllocator alloc(8192);
void *remember_me = alloc.allocate(0);
for (int i = 0; i < 1000; i++)
  do_something_with (alloc.allocate(12));
alloc.free_since (remember_me);

Note, that we don't need to remember all the pointers to the 12-byte objects for freeing them. The free_since() does deallocate them all at once.

Parameters

ptr	Pointer as returned by allocate(). It acts like a kind of mark of a certain position in the stack of all objects, off which you can throw away everything above that mark.

Definition at line 240 of file kallocator.cpp.

initHash()

void TDEZoneAllocator::initHash ( )

protected

Reinitialize hash list.

Definition at line 122 of file kallocator.cpp.

Member Data Documentation

blockOffset

unsigned long TDEZoneAllocator::blockOffset

protected

Store offset into current block; size-offset is free.

Definition at line 125 of file kallocator.h.

blockSize

unsigned long TDEZoneAllocator::blockSize

protected

Store block size from constructor.

Definition at line 123 of file kallocator.h.

currentBlock

MemBlock* TDEZoneAllocator::currentBlock

protected

One block is 'current' to satisfy requests.

Definition at line 121 of file kallocator.h.

hashDirty

bool TDEZoneAllocator::hashDirty

protected

Flag the hashes as in need of reorganization.

Definition at line 135 of file kallocator.h.

hashList

MemList** TDEZoneAllocator::hashList

protected

Collection of lists of blocks, for lookups.

Definition at line 131 of file kallocator.h.

hashSize

unsigned int TDEZoneAllocator::hashSize

protected

Count of hashes.

Definition at line 133 of file kallocator.h.

log2

unsigned int TDEZoneAllocator::log2

protected

base-2 log of the block size.

Definition at line 127 of file kallocator.h.

num_blocks

unsigned int TDEZoneAllocator::num_blocks

protected

Count total number of allocated blocks.

Definition at line 129 of file kallocator.h.

---

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

• kallocator.h
• kallocator.cpp