Feature #20408: Add heap_live_slots to GC.stat_heap

• Status: Closed
• Assignee: -
• Target version: -

[mk (Matthias Käppler)]

GC.stat exposes a heap_live_slots metric that returns the number of live objects occupying eden slots.

Because the slot size was fixed to RVALUE_SIZE, this allowed for some basic approximations of how many bytes were live/in-use (heap_live_slots * RVALUE_SIZE).
This could furthermore be "embellished" by adding malloc'ed memory for those objects that were larger than a 40B slot (we track this via a custom CRuby patch).

However, with the addition of Variable Width Allocations (https://bugs.ruby-lang.org/issues/18239), this does not work anymore because we don't know how heap_live_slots distributes over all pools that use different slot sizes.

This could be addressed by also adding heap_live_slots (and for symmetry: heap_free_slots) to GC.stat_heap. The sum of all live slots per pool should equal GC.stat[:heap_live_slots].

[mk (Matthias Käppler)]

• Description updated (diff)

[peterzhu2118 (Peter Zhu)]

Thank you for this ticket. I opened a PR that implements this feature: https://github.com/ruby/ruby/pull/10439

[mk (Matthias Käppler)]

peterzhu2118 (Peter Zhu) wrote in #note-2:

Thank you for this ticket. I opened a PR that implements this feature: https://github.com/ruby/ruby/pull/10439

Thank you so much Peter! <3

[peterzhu2118 (Peter Zhu)]

• Status changed from Open to Closed

Applied in changeset git|fa02d7a01f5e7516de8eb3c7f92ec75c50c06e3f.

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Implement heap_live_slots in GC.stat_heap

[Feature #20408]