Bug ID: JDK-6924259 Remove String.count/String.offset/String.hashcode

JDK-6924259 : Remove String.count/String.offset/String.hashcode

Type: Enhancement
Component: hotspot
Sub-Component: compiler
Affected Version: hs17,1.4.0,5.0,6

Priority: P3
Status: Closed
Resolution: Fixed
OS: generic,windows_nt,windows_xp
CPU: generic,x86

Submitted: 2010-02-08
Updated: 2017-11-25
Resolved: 2013-07-18

Versions (Unresolved/Resolved/Fixed)

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Unresolved : Release in which this issue/RFE will be addressed.
Resolved: Release in which this issue/RFE has been resolved.
Fixed : Release in which this issue/RFE has been fixed. The release containing this fix may be available for download as an Early Access Release or a General Availability Release.

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JDK 7	JDK 8	Other
7u40Fixed	8Fixed	hs23.2Fixed

Related Reports

Duplicate :	JDK-4513622 - (str) keeping a substring of a field prevents GC for object
Relates :	JDK-7175133 - jinfo failed to get system properties after 6924259
Relates :	JDK-7177128 - SA cannot get correct system properties after 7126277
Relates :	JDK-7165776 - Update Java VisualVM binaries in 7u6 and 8
Relates :	JDK-7197183 - (str) String.substring and String.subsequence performance slower since 7u6
Relates :	JDK-7133390 - De-duplication of Fields of Immutable Objects (Strings)
Relates :	JDK-8136399 - json lib is slow on Linux 64 Java 8
Relates :	JDK-7173329 - Fix broken commit of 7126277 to 7u6-dev
Relates :	JDK-8191874 - (str) Need String alternative with shared storage

Description

Investigate the performance impacts of removing String.count, String.offset,
and String.hashcode on various industry standard benchmarks.
There are no new regression tests for this change because the API is not impacted. It is a behind-the-scenes performance/implementation change only

Comments

EVALUATION http://hg.openjdk.java.net/lambda/lambda/hotspot/rev/8f972594effc
29-06-2012
EVALUATION http://hg.openjdk.java.net/hsx/hotspot-rt/hotspot/rev/8f972594effc
26-05-2012
EVALUATION http://hg.openjdk.java.net/hsx/hsx23.2/hotspot/rev/3facbb14e873
23-05-2012
EVALUATION http://hg.openjdk.java.net/hsx/hotspot-comp/hotspot/rev/8f972594effc
14-05-2012
EVALUATION A working change has been developed that allows a version of the String class that doesn't use the count/offset fields. However, it's not possible to eliminate the hashcode field. This fix also works with compressed strings. At this point, the fix is on hold as other priorities have taken precedence.
12-11-2010