Feature #19355
open
Add finer coarsed locking for searching callable method entries
Description
During multi-ractor mode, unfortunately when calling methods often there's a call to the internal cruby function callable_method_entry, which
returns a cached CME or a new one. In the case that it's cached, there's a VM lock around its access that could be reduced to a lock
pertaining to the class of the caller of the method. This reduces locking in multi-ractor mode and allows, for example, object allocation to happen
at the same time as method calls.
Updated by luke-gru (Luke Gruber) almost 3 years ago
MyClass = Object class MyClass2 < Object; def call_a_method [] end def call_another_method {} end end USE_RACTORS = ARGV.first == "ractor" puts "ractors: #{USE_RACTORS ? 't' : 'f'}" class FakeRactor def initialize yield self end def take end end def concurrency(&blk) if USE_RACTORS Ractor.new(&blk) else FakeRactor.new(&blk) end end bench = Benchmark.measure do rs = [] 100.times do rs << concurrency do 50_000.times do|i| obj = MyClass.new obj.respond_to?(:hi) obj2 = MyClass2.new obj2.respond_to?(:hi) obj2.call_a_method obj2.call_another_method end end end rs.each(&:take) end puts bench On my machine without my local patch, it takes 6.5 seconds and with the patch 5.5 seconds.
Of course storing a mutex on every class instance takes more memory so it might not be worth
it But with this new mutex it's possible also to do constant lookup / update without the VM
lock too.