From: "Eregon (Benoit Daloze)" Date: 2021-12-13T21:56:46+00:00 Subject: [ruby-core:106646] [Ruby master Feature#18364] Add GC.stat_pool for Variable Width Allocation Issue #18364 has been updated by Eregon (Benoit Daloze). peterzhu2118 (Peter Zhu) wrote in #note-10: > Thank you for the summary @mame! We'll extend `GC.stat` to return a nested data structure. This seems incompatible and might break existing code which expects `GC.stat` to return a `Hash[Symbol,Integer]`. Also what should `size_t rb_gc_stat(VALUE)` return/raise for such a case? Also it's likely to make `GC.stat()`/`GC.stat(hash)` slower and use more allocations, which seems suboptimal. Notably, `GC.stat(hash)` no longer avoids allocations and becomes useless. I don't understand @matz's reasoning here, the OP and myself agreed `GC.stat_pool` is best and it covers both the VWA use-case and JRuby/TruffleRuby. The nested approach seems to have multiple issues, and a key like `size_heap` seems too specific (those details might change over time) and makes no sense for other Ruby implementations. Maybe it was missed in #4 that it's the result of `GC.heap_stats` on TruffleRuby, *not* of `GC.stat`? "memory pool" is a well established term in this area. Another method name is `stat_heap` if that sounds clearer. ---------------------------------------- Feature #18364: Add GC.stat_pool for Variable Width Allocation https://bugs.ruby-lang.org/issues/18364#change-95317 * Author: peterzhu2118 (Peter Zhu) * Status: Open * Priority: Normal * Assignee: matz (Yukihiro Matsumoto) ---------------------------------------- # GitHub PR: https://github.com/ruby/ruby/pull/5177 We're proposing an API to get statistics for size pools for Variable Width Allocation similar to `GC.stat`. This will make it easier for us (and other developers) to tune VWA. Before 3.1 release, we plan to keep this method hidden from the documentation using `:nodoc:` since it is not useful when not using VWA. For example: ```ruby # Get stats for size pool 2 puts GC.stat_pool(2) #=> {:slot_size=>160, :heap_allocatable_pages=>80, :heap_eden_pages=>14, :heap_eden_slots=>1424, :heap_tomb_pages=>0, :heap_tomb_slots=>0} puts GC.stat_pool(2, :heap_eden_pages) #=> 14 ``` We aim to keep the keys in the outputted hash the same as the keys used in `GC.stat`. We chose to implement a new method instead of re-using an existing API (`GC.stat`) because the keys returned by `GC.stat_pool` will not be the same as `GC.stat`. We believe that having `GC.stat` return different shapes of hashes based on its arguments is confusing. -- https://bugs.ruby-lang.org/ Unsubscribe: