JDK-8208658 : Make CDS archived heap regions usable even if compressed oop encoding has changed
- Type: Enhancement
- Component: hotspot
- Sub-Component: runtime
- Affected Version: 11
- Priority: P3
- Status: Resolved
- Resolution: Fixed
- Submitted: 2018-08-02
- Updated: 2020-08-08
- Resolved: 2018-08-22
The Version table provides details related to the release that this issue/RFE will be addressed.
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.
To download the current JDK release, click here.
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.
To download the current JDK release, click here.
| JDK 11 | JDK 12 |
|---|---|
| 11.0.7Fixed | 12 b09Fixed  |
Related Reports
|
Blocks :
|
|
|
Relates :
|
|
|
Relates :
|
|
|
Relates :
|
|
|
Relates :
|
|
|
Relates :
|
Description
At runtime, if you use a maximum heap size (-Xmx) setting that's different than the one used at CDS archive creation time, the archived heap regions may fail to map. The reason is the archived heap regions are hard-coded to a specific compressed oop encoding scheme This causes degradation in start-up. For the related code, see: http://hg.openjdk.java.net/jdk/jdk/file/5cc6acb1d6b6/src/hotspot/share/memory/filemap.cpp#l877 To fix this, we should patch/relocate the archived heap regions to make it compatible with the runtime compressed oop encoding. Preliminary result is encouraging. Test case: # dump archive java -Xshare:dump -Xmx2000m # same compressed oop encoding java -Xshare:on -Xmx2000m -Xlog:cds -version # different compressed oop encoding java -Xshare:on -Xmx2090m -Xlog:cds -version (The archive is dumped with UnscaledNarrowOop mode. At run time, if -Xmx2090m is specified, ZeroBasedNarrowOop is used instead). OLD same 34.45 ms +- 0.51% OLD diff 47.76 ms +- 0.61% <<<<< 13.3 ms degradation! NEW same 34.58 ms +- 0.94% NEW diff 35.09 ms +- 0.24% Patch: http://cr.openjdk.java.net/~iklam/jdk12/8208658-relocate-archived-heap-regions.v00/ Note that without this fix, start-up time degrades 13.3ms when compressed oop encoding has changed. With this fix, the degradation is only 0.5ms, which is the cost of relocating/patching the archived heap regions.
Comments
|