3 ms·

I think the hotspot's CMS old gen allocator used best-fit strategy since its collector didn't compact. But CMS has been deprecated because newer, compacting low

• hinkley 7y ago
  If memory serves, the new one uses an extra object header that points from the old object to the new one during move operations, and any reads of the old object get forwarded to the new one. I'm pretty sure that would have not performed well without the aggressive prediction logic in modern processors. Java 1's object accesses always read through an indirect pointer, but that went away in the name of performance, either when Hotspot was introduced, or on the next round of GC impromevents.
  • _old_dude_ 7y ago
    They are two new GCs Shenandoah and ZGC. Indirect pointers or Brooks pointers has it is called were used in Shenandoah v1 to allow an application thread that perform a read to not move the object during the evacuation phase. This strategy has been removed in Shenandoah v2 to have a better throughput so now both read and write by the application move the object during the evacuation phase. ZGC has never used Brooks pointers.
    • MaxBarraclough 7y ago
      I had to look up 'Brooks pointers'. For anyone else in this position, these two blog posts seem a good place to start: https://rkennke.wordpress.com/2013/10/23/shenandoah-gc-brooks-pointers/ https://rkennke.wordpress.com/2013/10/23/shenandoah-gc-brook... , https://blog.plan99.net/modern-garbage-collection-part-2-1c88847abcfd https://blog.plan99.net/modern-garbage-collection-part-2-1c8...