BlockAllocator (Jikes RVM API)

java.lang.Object
- org.mmtk.utility.alloc.BlockAllocator

```
public final class BlockAllocator
extends Object
```
This class implements "block" data structures of various sizes.
Blocks are a non-shared (thread-local) coarse-grained unit of storage. Blocks are available in power-of-two sizes.
Virtual memory space is taken from a VM resource, and pages consumed by blocks are accounted for by a memory resource.

Field Summary

Fields
Modifier and Type	Field and Description
`private static int`	`BLOCK_PAGE_OFFSET_SHIFT`
`private static byte`	`BLOCK_SC_MASK`
`static int`	`BLOCK_SIZE_CLASSES`
`private static Offset`	`BMD_OFFSET`
`private static Offset`	`CSC_OFFSET`
`private static Offset`	`FL_META_OFFSET`
`private static Offset`	`IU_OFFSET`
`private static int`	`LOG_BYTE_COVERAGE`
`private static int`	`LOG_BYTES_IN_BLOCK_META`
`static int`	`LOG_MAX_BLOCK`
`static int`	`LOG_MIN_BLOCK`
`private static int`	`MAX_BLOCK_PAGE_OFFSET`
`static byte`	`MAX_BLOCK_SIZE_CLASS`
`static int`	`META_DATA_BYTES_PER_REGION`
`static Extent`	`META_DATA_EXTENT`
`private static Offset`	`NEXT_OFFSET`

Constructor Summary

Constructors
Constructor and Description

BlockAllocator()

Constructors
Constructor and Description
`BlockAllocator()`

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static Address`	`alloc(Space space, int blockSizeClass)` Allocate a block, returning the address of the first usable byte in the block.
`static int`	`blockSize(int blockSizeClass)` Return the size in bytes of a block of a given size class
`static boolean`	`checkBlockMeta(Address block)` Return true if the metadata for this block was set.
`static void`	`clearBlockMeta(Address block)` Clear the metadata for this block
`static void`	`free(Space space, Address block)` Free a block.
`private static byte`	`getBlkSizeClass(Address address)` Get the block size class meta data field for a given page (all blocks on a given page are homogeneous with respect to block size class).
`static Address`	`getBlkStart(Address address)` Get the address of the start of a block size class a given page within the block.
`static byte`	`getClientSizeClass(Address address)` Get the client size class meta data field for a given page (all blocks on a given page are homogeneous with respect to block size class).
`static Address`	`getFreeListMeta(Address address)` Get the free list meta data field for a given address (this is per-block meta data that is stored along with the block metadata but not used by the block allocator).
`private static Address`	`getMetaAddress(Address address)` Get the address of some metadata given the address for which the metadata is required and the offset into the metadata that is of interest.
`private static Address`	`getMetaAddress(Address address, Offset offset)` Get the address of some metadata given the address for which the metadata is required and the offset into the metadata that is of interest.
`static Address`	`getNext(Address address)` Get the prev meta data field for a given address
`static void`	`markBlockMeta(Address block)` Mark the metadata for this block.
`static void`	`markBlockMeta(ObjectReference ref)` Marks the metadata for this block.
`private static int`	`pagesForSizeClass(int blockSizeClass)` Return the number of pages required when allocating space for this size class.
`static void`	`setAllClientSizeClass(Address block, int blocksc, byte sc)` Set the client size class meta data field for a given address (all blocks on a given page are homogeneous with respect to block size class).
`private static void`	`setBlkSizeMetaData(Address block, byte sc)` Set the block size class meta data field for a given address (all blocks on a given page are homogeneous with respect to block size class).
`static void`	`setFreeListMeta(Address address, Address value)` Set the free list meta data field for a given address (this is per-block meta data that is stored along with the block metadata but not used by the block allocator).
`static void`	`setNext(Address address, Address prev)` Set the prev meta data field for a given address

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - LOG_MIN_BLOCK
```
public static final int LOG_MIN_BLOCK
```
    See Also:
    
    Constant Field Values
  - LOG_MAX_BLOCK
```
public static final int LOG_MAX_BLOCK
```
    See Also:
    
    Constant Field Values
  - MAX_BLOCK_SIZE_CLASS
```
public static final byte MAX_BLOCK_SIZE_CLASS
```
    See Also:
    
    Constant Field Values
  - BLOCK_SIZE_CLASSES
```
public static final int BLOCK_SIZE_CLASSES
```
    See Also:
    
    Constant Field Values
  - NEXT_OFFSET
```
private static final Offset NEXT_OFFSET
```
  - BMD_OFFSET
```
private static final Offset BMD_OFFSET
```
  - CSC_OFFSET
```
private static final Offset CSC_OFFSET
```
  - IU_OFFSET
```
private static final Offset IU_OFFSET
```
  - FL_META_OFFSET
```
private static final Offset FL_META_OFFSET
```
  - BLOCK_SC_MASK
```
private static final byte BLOCK_SC_MASK
```
    See Also:
    
    Constant Field Values
  - BLOCK_PAGE_OFFSET_SHIFT
```
private static final int BLOCK_PAGE_OFFSET_SHIFT
```
    See Also:
    
    Constant Field Values
  - MAX_BLOCK_PAGE_OFFSET
```
private static final int MAX_BLOCK_PAGE_OFFSET
```
    See Also:
    
    Constant Field Values
  - LOG_BYTES_IN_BLOCK_META
```
private static final int LOG_BYTES_IN_BLOCK_META
```
  - LOG_BYTE_COVERAGE
```
private static final int LOG_BYTE_COVERAGE
```
  - META_DATA_BYTES_PER_REGION
```
public static final int META_DATA_BYTES_PER_REGION
```
  - META_DATA_EXTENT
```
public static final Extent META_DATA_EXTENT
```
- Constructor Detail
  - BlockAllocator
```
public BlockAllocator()
```
- Method Detail
  - alloc
```
public static Address alloc(Space space,
                            int blockSizeClass)
```
    Allocate a block, returning the address of the first usable byte in the block.
    
    Parameters:
    
    space - the space to request the memory from
    
    blockSizeClass - The size class for the block to be allocated.
    
    Returns:
    
    The address of the first usable byte in the block, or zero on failure.
  - free
```
public static void free(Space space,
                        Address block)
```
    Free a block. If the block is a sub-page block and the page is not completely free, then the block is added to the free list. Otherwise the block is returned to the virtual memory resource.
    
    Parameters:
    
    space - the space that contains the block
    
    block - The address of the block to be freed
  - blockSize
```
public static int blockSize(int blockSizeClass)
```
    Return the size in bytes of a block of a given size class
    
    Parameters:
    
    blockSizeClass - The size class in question
    
    Returns:
    
    The size in bytes of a block of this size class
  - pagesForSizeClass
```
private static int pagesForSizeClass(int blockSizeClass)
```
    Return the number of pages required when allocating space for this size class.
    
    Parameters:
    
    blockSizeClass - The size class in question
    
    Returns:
    
    The number of pages required when allocating a block (or blocks) of this size class.
  - setBlkSizeMetaData
```
private static void setBlkSizeMetaData(Address block,
                                       byte sc)
```
    Set the block size class meta data field for a given address (all blocks on a given page are homogeneous with respect to block size class).
    
    Parameters:
    
    block - The address of interest
    
    sc - The value to which this field is to be set
  - getBlkSizeClass
```
private static byte getBlkSizeClass(Address address)
```
    Get the block size class meta data field for a given page (all blocks on a given page are homogeneous with respect to block size class).
    
    Parameters:
    
    address - The address of interest
    
    Returns:
    
    The size class field for the block containing the given address
  - getBlkStart
```
public static Address getBlkStart(Address address)
```
    Get the address of the start of a block size class a given page within the block.
    
    Parameters:
    
    address - The address of interest
    
    Returns:
    
    The address of the block containing the address
  - setAllClientSizeClass
```
public static void setAllClientSizeClass(Address block,
                                         int blocksc,
                                         byte sc)
```
    Set the client size class meta data field for a given address (all blocks on a given page are homogeneous with respect to block size class).
    
    Parameters:
    
    block - The address of interest
    
    blocksc - the block's size class
    
    sc - The value to which this field is to be set
  - getClientSizeClass
```
public static byte getClientSizeClass(Address address)
```
    Get the client size class meta data field for a given page (all blocks on a given page are homogeneous with respect to block size class).
    
    Parameters:
    
    address - The address of interest
    
    Returns:
    
    The size class field for the block containing the given address
  - setFreeListMeta
```
public static void setFreeListMeta(Address address,
                                   Address value)
```
    Set the free list meta data field for a given address (this is per-block meta data that is stored along with the block metadata but not used by the block allocator).
    
    Parameters:
    
    address - The address of interest
    
    value - The value to which this field is to be set
  - getFreeListMeta
```
public static Address getFreeListMeta(Address address)
```
    Get the free list meta data field for a given address (this is per-block meta data that is stored along with the block metadata but not used by the block allocator).
    
    Parameters:
    
    address - The address of interest
    
    Returns:
    
    The free list meta data field for the block containing the given address
  - setNext
```
public static void setNext(Address address,
                           Address prev)
```
    Set the prev meta data field for a given address
    
    Parameters:
    
    address - The address of interest
    
    prev - The value to which this field is to be set
  - getNext
```
public static Address getNext(Address address)
```
    Get the prev meta data field for a given address
    
    Parameters:
    
    address - The address of interest
    
    Returns:
    
    The prev field for the block containing the given address
  - getMetaAddress
```
private static Address getMetaAddress(Address address)
```
    Get the address of some metadata given the address for which the metadata is required and the offset into the metadata that is of interest.
    
    Parameters:
    
    address - The address for which the metadata is required
    
    Returns:
    
    The address of the specified meta data
  - getMetaAddress
```
private static Address getMetaAddress(Address address,
                                      Offset offset)
```
    Get the address of some metadata given the address for which the metadata is required and the offset into the metadata that is of interest.
    
    Parameters:
    
    address - The address for which the metadata is required
    
    offset - The offset (in bytes) into the metadata block (eg for the prev pointer, or next pointer)
    
    Returns:
    
    The address of the specified meta data
  - markBlockMeta
```
public static void markBlockMeta(ObjectReference ref)
```
    Marks the metadata for this block.
    
    Parameters:
    
    ref - the block's reference
  - markBlockMeta
```
public static void markBlockMeta(Address block)
```
    Mark the metadata for this block.
    
    Parameters:
    
    block - The block address
  - checkBlockMeta
```
public static boolean checkBlockMeta(Address block)
```
    Return true if the metadata for this block was set.
    
    Parameters:
    
    block - The block address
    
    Returns:
    
    value of the meta data.
  - clearBlockMeta
```
public static void clearBlockMeta(Address block)
```
    Clear the metadata for this block
    
    Parameters:
    
    block - The block address

Class BlockAllocator

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LOG_MIN_BLOCK

LOG_MAX_BLOCK

MAX_BLOCK_SIZE_CLASS

BLOCK_SIZE_CLASSES

NEXT_OFFSET

BMD_OFFSET

CSC_OFFSET

IU_OFFSET

FL_META_OFFSET

BLOCK_SC_MASK

BLOCK_PAGE_OFFSET_SHIFT

MAX_BLOCK_PAGE_OFFSET

LOG_BYTES_IN_BLOCK_META

LOG_BYTE_COVERAGE

META_DATA_BYTES_PER_REGION

META_DATA_EXTENT

Constructor Detail

BlockAllocator

Method Detail

alloc

free

blockSize

pagesForSizeClass

setBlkSizeMetaData

getBlkSizeClass

getBlkStart

setAllClientSizeClass

getClientSizeClass

setFreeListMeta

getFreeListMeta

setNext

getNext

getMetaAddress

getMetaAddress

markBlockMeta

markBlockMeta

checkBlockMeta

clearBlockMeta