KZoneAllocator Class Reference

#include <KZoneAllocator>

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

Protected Types
typedef QList< MemBlock * >	MemList

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

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 than 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 47 of file kallocator.h.

Member Typedef Documentation

typedef QList<MemBlock *> KZoneAllocator::MemList

protected

A list of chunks.

Definition at line 114 of file kallocator.h.

Constructor & Destructor Documentation

KZoneAllocator::KZoneAllocator ( unsigned long  _blockSize = 8*1024 )

explicit

Creates a KZoneAllocator object.

Parameters

_blockSize

Size in bytes of the blocks requested from malloc.

Definition at line 79 of file kallocator.cpp.

KZoneAllocator::~KZoneAllocator

(

)

Destructs the ZoneAllocator and free all memory allocated by it.

Definition at line 92 of file kallocator.cpp.

Member Function Documentation

void KZoneAllocator::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 136 of file kallocator.cpp.

void * KZoneAllocator::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 218 of file kallocator.cpp.

void KZoneAllocator::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 KZoneAllocator 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 241 of file kallocator.cpp.

void KZoneAllocator::delBlock ( MemBlock *  b )

protected

Delete a memory block.

This really returns the memory to the heap.

Parameters

b	block to delete

Definition at line 182 of file kallocator.cpp.

void KZoneAllocator::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:

KZoneAllocator 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 274 of file kallocator.cpp.

void KZoneAllocator::initHash ( )

protected

Reinitialize hash list.

Definition at line 156 of file kallocator.cpp.

void KZoneAllocator::insertHash ( MemBlock *  b )

protected

Definition at line 117 of file kallocator.cpp.

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

• kallocator.h
• kallocator.cpp