Can GC implementations provide a cheap estimation of live set size?

[Jaroslav Bachorík]

Hello,

In connection with https://bugs.openjdk.java.net/browse/JDK-8258431 I
am trying to figure out whether providing a cheap estimation of live
set size is something actually achievable across various GC
implementations.

What I am looking at is piggy-backing on a concurrent mark task to get
the summary size of live objects - using the 'straight-forward'
heap-inspection like approach is prohibitively expensive.

Thanks and regards,

-JB-