, 0012 opt_regexpmatch2 [CcCr] 0014 leave ``` The ISeq object contains two entries in the `is_entries` buffer, one for the `ISE` cache associated with the `once` instruction, and one for the `IC` cache associated with the `opt_getinlinecache` and `opt_setinlinecache` instructions. Unfortunately we cannot iterate through the caches in the `is_entries` list because the union types don't have the same layout. [Marking an `ISE`](https://github.com/ruby/ruby/blob/744d17ff6c33b09334508e8110007ea2a82252f5/iseq.c#L296-L306) is very different than [marking an `IC`](https://github.com/ruby/ruby/blob/744d17ff6c33b09334508e8110007ea2a82252f5/iseq.c#L270-L280), and we can only differentiate them by disassembling and checking the instruction sequences themselves. To solve this problem, this PR introduces [3 counters for the different types of inline caches](https://github.com/ruby/ruby/compare/master...tenderlove:iseq-bitmap?expand=1#diff-2989766b46aac389cc58ca9c83fac2bb85c03f3a3d37b176b4be673c9d56e0e4R463-R465). Then, we group inline cache types within the `is_entries` buffer. Since the inline cache types are grouped, we can use the counters to iterate over the buffer and we know what type is being used. Combining bitmap marking and inline cache arrangement means that we can mark instruction sequences without disassembling the instructions. ## Speed impact I benchmarked this change with a basic Rails application using the following script: ```ruby puts RUBY_DESCRIPTION require "benchmark/ips" Benchmark.ips do |x| x.report("major GC") { GC.start } end ``` Here are the results with the master version of Ruby: ``` $ RAILS_ENV=production gel exec bin/rails r test.rb ruby 3.2.0dev (2022-06-22T12:30:39Z master 744d17ff6c) [arm64-darwin21] Warming up -------------------------------------- major GC 4.000 i/100ms Calculating ------------------------------------- major GC 47.748 (�� 2.1%) i/s - 240.000 in 5.028520s ``` Here it is with these patches applied: ``` $ RAILS_ENV=production gel exec bin/rails r test.rb ruby 3.2.0dev (2022-06-22T20:52:13Z iseq-bitmap 2ba736a7f9) [arm64-darwin21] Warming up -------------------------------------- major GC 7.000 i/100ms Calculating ------------------------------------- major GC 77.208 (�� 1.3%) i/s - 392.000 in 5.079023s ``` With these patches applied, major GC is about 60% faster. ## Memory impact The memory increase is proportional to the number of instructions stored on an iseq. This works about to be about 1% increase in the size of an iseq (`ceil(iseq_length / 64)` on 64 bit platforms). ## Future work This PR always mallocs a bitmap table. We can eliminate the malloc when: 1. There is nothing to mark 2. iseq_length is <= 64 I posted a [pull request on GitHub](https://github.com/ruby/ruby/pull/6053), and I've attached a squashed version of the patches. The diff includes some unused code which I used to verify the bitmaps. If we decide to merge this I'll remove the unused code. ---Files-------------------------------- 0001-Squashed-commit-of-the-following.patch (23.6 KB) -- https://bugs.ruby-lang.org/ Unsubscribe: