com.oracle.svm.core.threadlocal

Class FastThreadLocal

java.lang.Object

com.oracle.svm.core.threadlocal.FastThreadLocal

Direct Known Subclasses:

FastThreadLocalBytes, FastThreadLocalInt, FastThreadLocalLong, FastThreadLocalObject, FastThreadLocalWord

public abstract class FastThreadLocal
extends Object

Base class for fast thread local variables.

Field Summary

Fields

Modifier and Type	Field and Description
static int	BYTE_OFFSET Useful value for FastThreadLocal.setMaxOffset(int): The thread local variable has an offset that can be expressed as a signed 8-bit value.
static int	FIRST_CACHE_LINE Useful value for FastThreadLocal.setMaxOffset(int): The thread local variable is in the first cache line of the memory block.

Method Summary

Modifier and Type	Method and Description
boolean	getAllowFloatingReads() Returns true if the floating reads is enabled, else false.
org.graalvm.word.LocationIdentity	getLocationIdentity() Returns the LocationIdentity used for memory accesses performed by the get and set methods of the subclasses.
int	getMaxOffset()
String	getName()
<T extends FastThreadLocal> T	setAllowFloatingReads(boolean allow) Sets whether non-volatile fast thread local reads can be read using floating semantics in the compiler graph.
<T extends FastThreadLocal> T	setMaxOffset(int maxOffset) Sets the maximum offset of this thread local variable in the memory block reserved for each thread.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

FIRST_CACHE_LINE

public static final int FIRST_CACHE_LINE

Useful value for FastThreadLocal.setMaxOffset(int): The thread local variable is in the first cache line of the memory block. This allows grouping of the most frequently accessed variables. We are not using a real cache line size, but instead assume that 64 bytes is the common minimum size on all platforms.

See Also:

Constant Field Values

BYTE_OFFSET

public static final int BYTE_OFFSET

Useful value for FastThreadLocal.setMaxOffset(int): The thread local variable has an offset that can be expressed as a signed 8-bit value. Some architectures, e.g. AMD64, need fewer bytes to encode such offsets.

See Also:

Constant Field Values

Method Detail

getLocationIdentity

public org.graalvm.word.LocationIdentity getLocationIdentity()

Returns the LocationIdentity used for memory accesses performed by the get and set methods of the subclasses.

setMaxOffset

public <T extends FastThreadLocal> T setMaxOffset(int maxOffset)

Sets the maximum offset of this thread local variable in the memory block reserved for each thread. This can be used for performance and footprint optimization, to group frequently accessed values closely together with low offsets that can be encoded more efficiently in machine code.

getMaxOffset

public int getMaxOffset()

setAllowFloatingReads

public <T extends FastThreadLocal> T setAllowFloatingReads(boolean allow)

Sets whether non-volatile fast thread local reads can be read using floating semantics in the compiler graph. If this is set to false (default) then reads will always remain fixed in the graph and do not move. If this is set to true then reads can float according to the location identity of the fast thread local.

getAllowFloatingReads

public boolean getAllowFloatingReads()

Returns true if the floating reads is enabled, else false.

See Also:

FastThreadLocal.setAllowFloatingReads(boolean)

getName

public String getName()