util/concurrent/Contended.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

package java.util.concurrent;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * An annotation expressing that objects and/or their fields are
 * expected to encounter memory contention, generally in the form of
 * "false sharing". This annotation serves as a hint that such objects
 * and fields should reside in locations isolated from those of other
 * objects or fields. The effects of this annotation will nearly
 * always add space overhead to programs.  Its use is warranted only
 * when the performance impact of this time/space tradeoff is
 * intrinsically worthwhile; for example, in concurrent contexts in
 * which each instance of the annotated object is often accessed by a
 * different thread.
 *
 * <p>A {@code @Contended} field annotation may optionally include a
 * contention group tag. All fields with the same tag are considered
 * as a group with respect to isolation from other groups. A default
 * annotation without a tag indicates contention with all other
 * fields, including other {@code @Contended} ones.

 * <p>When the annotation is used at the class level, all unannotated
 * fields of the object are considered to be in the same default
 * group, separate from any fields that carry their own (possibly
 * tagged) {@code @Contended} annotations.
 *
 * <p><b>Sample Usages</b>. (Forthcoming.)
 *
 * @since 1.8
 */
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.TYPE})
public @interface Contended {
    /**
     * The (optional) contention group tag.
     */
    String value() default "";
}
Revision:	1.1
Committed:	Mon Nov 26 21:33:42 2012 UTC (11 years, 6 months ago) by dl
Branch:	MAIN
Log Message:	Initial version
#	User	Rev	Content
1	dl	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/publicdomain/zero/1.0/
5			*/
6
7			package java.util.concurrent;
8
9			import java.lang.annotation.ElementType;
10			import java.lang.annotation.Retention;
11			import java.lang.annotation.RetentionPolicy;
12			import java.lang.annotation.Target;
13
14			/**
15			* An annotation expressing that objects and/or their fields are
16			* expected to encounter memory contention, generally in the form of
17			* "false sharing". This annotation serves as a hint that such objects
18			* and fields should reside in locations isolated from those of other
19			* objects or fields. The effects of this annotation will nearly
20			* always add space overhead to programs. Its use is warranted only
21			* when the performance impact of this time/space tradeoff is
22			* intrinsically worthwhile; for example, in concurrent contexts in
23			* which each instance of the annotated object is often accessed by a
24			* different thread.
25			*
26			* <p>A {@code @Contended} field annotation may optionally include a
27			* contention group tag. All fields with the same tag are considered
28			* as a group with respect to isolation from other groups. A default
29			* annotation without a tag indicates contention with all other
30			* fields, including other {@code @Contended} ones.
31
32			* <p>When the annotation is used at the class level, all unannotated
33			* fields of the object are considered to be in the same default
34			* group, separate from any fields that carry their own (possibly
35			* tagged) {@code @Contended} annotations.
36			*
37			* <p><b>Sample Usages</b>. (Forthcoming.)
38			*
39			* @since 1.8
40			*/
41			@Retention(RetentionPolicy.RUNTIME)
42			@Target({ElementType.FIELD, ElementType.TYPE})
43			public @interface Contended {
44			/**
45			* The (optional) contention group tag.
46			*/
47			String value() default "";
48			}