JDK-8233093 : Move CDS heap oopmaps into new MetaspaceShared::bm region
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: runtime
  • Affected Version: 14
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2019-10-29
  • Updated: 2020-04-07
  • Resolved: 2020-03-26
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JDK 15
15 b17Fixed
Related Reports
Blocks :  
JDK-8231610 - Relocate the CDS archive if it cannot be mapped to the requested address
Description
After JDK-8231610 (Relocate the CDS archive if it cannot be mapped to the requested address), we will have a new "bm" region that's used only during archive loading, and will be unmapped afterwards to save memory footprint. This region will be a good place for the CDSFileMapRegion::oopmap, which is also needed only during archive loading.

http://hg.openjdk.java.net/jdk/jdk/file/13ad9a1bac18/src/hotspot/share/include/cds.h#l53
Comments
URL: https://hg.openjdk.java.net/jdk/jdk/rev/5ac19bd3a1e2 User: ccheung Date: 2020-03-26 17:15:10 +0000
26-03-2020
webrev: http://cr.openjdk.java.net/~ccheung/jdk15/8233093/webrev.00/ Before: [0.753s][debug][cds] ro space: 7552120 [ 59.7% of total] out of 7553024 bytes [100.0% used] at 0x00000008003e1000 [0.753s][debug][cds] bm space: 184320 [ 1.5% of total] out of 184320 bytes [100.0% used] at 0x0000000000000000 After: [0.766s][debug][cds] ro space: 7525856 [ 59.5% of total] out of 7528448 bytes [100.0% used] at 0x00000008003e1000 [0.766s][debug][cds] bm space: 208896 [ 1.7% of total] out of 208896 bytes [100.0% used] at 0x0000000000000000 Since the CDS heap oopmaps have been moved from the ro to the bm region, with the fix, the size of the ro region will be decreased and the size of the bm region will be increased.
25-03-2020