From: "k0kubun (Takashi Kokubun)" Date: 2022-06-15T07:53:58+00:00 Subject: [ruby-core:108925] [Ruby master Misc#18830] Remove MJIT worker thread Issue #18830 has been reported by k0kubun (Takashi Kokubun). ---------------------------------------- Misc #18830: Remove MJIT worker thread https://bugs.ruby-lang.org/issues/18830 * Author: k0kubun (Takashi Kokubun) * Status: Open * Priority: Normal ---------------------------------------- ## Proposal * Remove MJIT worker thread * Compiling ISeq to C should synchronously happen in Ruby threads * Unix platforms asynchronously wait for a C compiler process to finish using SIGCHLD, and MSWIN synchronously waits for a C compiler process to finish. Note: The architecture is similar to what we did for the timer thread [Misc #14937]. Removing the MJIT worker thread using SIGCHLD is what @normalperson proposed before too. ## Motivation * It's hard to maintain a JIT compiler if it can't touch Ruby VM. Many C functions in CRuby rely on the VM behind the scenes. * It's hard to maintain a JIT compiler if it can't trigger GC. Not only you cannot use `xmalloc`, but also you have to fight race conditions with GC and SEGV caused by them. ## Assumptions * The bottleneck of MJIT compilation is the time taken to wait for a C compiler process to finish. Thus compiling ISeq to C will not be a bottleneck. Potentially, this cost could be insignificant even if we rewrite the entire ISeq -> C compiler in Ruby. * Nobody really uses MJIT on MSWIN. If the maintenance cost becomes too high because of the MSWIN-specific implementation introduced by this change, it's okay to just remove the support. --- Patch: https://github.com/ruby/ruby/pull/6006 The motivation for this change is not about improving performance by itself, but this makes it slightly faster. ``` $ benchmark-driver benchmark.yml --rbenv 'before --mjit;after --mjit' -v --repeat-count=12 --output=all --alternate before --mjit: ruby 3.2.0dev (2022-06-15T05:42:09Z master 46706e7808) +MJIT [x86_64-linux] after --mjit: ruby 3.2.0dev (2022-06-15T07:21:31Z no-mjit-worker 90433da34d) +MJIT [x86_64-linux] Calculating ------------------------------------- before --mjit after --mjit Optcarrot Lan_Master.nes 125.3789474179577 129.6361842567196 fps 125.7892049665125 130.1237905211524 126.3359252053467 131.3352551857975 127.2303480033240 131.5128102697965 127.2368143596796 131.9221842055012 127.3938219177180 131.9712318537562 127.8370994014408 132.0527716303878 127.9904178998168 132.4032777876095 128.0631040346902 132.4425814311906 128.3016029706804 132.5687514040249 128.8733290749460 132.7843477576762 129.5397101458566 133.4416009274654 ``` -- https://bugs.ruby-lang.org/ Unsubscribe: