org.apache.flink.runtime.memorymanager

Interface MemoryManager

All Known Implementing Classes:

DefaultMemoryManager

public interface MemoryManager

Interface for a memory manager that assigns portions of memory to different tasks. Each allocated segment of memory is specific to a task. Memory segments can be freed individually, or all memory allocated by a task can be freed as a whole.

Internally, memory is represented as byte arrays. The memory manager acts like a distributer for memory, which means it assigns portions of the arrays to tasks. If memory is released, it means that this part of the memory can be assigned to other tasks.

Method Summary

Methods

Modifier and Type	Method and Description
List<MemorySegment>	allocatePages(AbstractInvokable owner, int numPages)
void	allocatePages(AbstractInvokable owner, List<MemorySegment> target, int numPages)
long	computeMemorySize(double fraction) Computes the memory size of the fraction per slot.
int	computeNumberOfPages(double fraction) Computes to how many pages the given number of bytes corresponds.
long	getMemorySize() Returns the total size of memory.
int	getPageSize() Gets the size of the pages handled by the memory manager.
<T extends MemorySegment> void	release(Collection<T> segments) Tries to release the memory for the specified collection of segments.
void	release(MemorySegment segment) Tries to release the memory for the specified segment.
void	releaseAll(AbstractInvokable task) Releases all memory segments for the given task.
long	roundDownToPageSizeMultiple(long numBytes) Rounds the given value down to a multiple of the memory manager's page size.
void	shutdown() Shuts the memory manager down, trying to release all the memory it managed.
boolean	verifyEmpty() Checks if the memory manager all memory available and the descriptors of the free segments describe a contiguous memory layout.

Method Detail

allocatePages

List<MemorySegment> allocatePages(AbstractInvokable owner,
                                int numPages)
                                  throws MemoryAllocationException

Throws:

MemoryAllocationException

allocatePages

void allocatePages(AbstractInvokable owner,
                 List<MemorySegment> target,
                 int numPages)
                   throws MemoryAllocationException

Throws:

MemoryAllocationException

release

void release(MemorySegment segment)

Tries to release the memory for the specified segment. If the segment has already been released or is null, the request is simply ignored. If the segment is not from the expected MemorySegment implementation type, an IllegalArgumentException is thrown.

Parameters:

segment - The segment to be released.

Throws:

IllegalArgumentException - Thrown, if the given segment is of an incompatible type.

release

<T extends MemorySegment> void release(Collection<T> segments)

Tries to release the memory for the specified collection of segments.

Type Parameters:

T - The type of memory segment.

Parameters:

segments - The segments to be released.

Throws:

NullPointerException - Thrown, if the given collection is null.

IllegalArgumentException - Thrown, id the segments are of an incompatible type.

releaseAll

void releaseAll(AbstractInvokable task)

Releases all memory segments for the given task.

Parameters:

task - The task whose memory segments are to be released.

getPageSize

int getPageSize()

Gets the size of the pages handled by the memory manager.

Returns:

The size of the pages handled by the memory manager.

getMemorySize

long getMemorySize()

Returns the total size of memory.

Returns:

The total size of memory.

computeNumberOfPages

int computeNumberOfPages(double fraction)

Computes to how many pages the given number of bytes corresponds. If the given number of bytes is not an exact multiple of a page size, the result is rounded down, such that a portion of the memory (smaller than the page size) is not included.

Parameters:

fraction - the fraction of the total memory per slot

Returns:

The number of pages to which

computeMemorySize

long computeMemorySize(double fraction)

Computes the memory size of the fraction per slot.

Parameters:

fraction - The fraction of the memory of the task slot.

Returns:

The number of pages corresponding to the memory fraction.

roundDownToPageSizeMultiple

long roundDownToPageSizeMultiple(long numBytes)

Rounds the given value down to a multiple of the memory manager's page size.

Returns:

The given value, rounded down to a multiple of the page size.

shutdown

void shutdown()

Shuts the memory manager down, trying to release all the memory it managed. Depending on implementation details, the memory does not necessarily become reclaimable by the garbage collector, because there might still be references to allocated segments in the code that allocated them from the memory manager.

verifyEmpty

boolean verifyEmpty()

Checks if the memory manager all memory available and the descriptors of the free segments describe a contiguous memory layout.

Returns:

True, if the memory manager is empty and valid, false if it is not empty or corrupted.