128039 2014-01-31 22:22:35 -0800 Improve convergence on Octane2/gbemu 2014-04-29 14:42:44 -0700 1 1 1 Unclassified WebKit JavaScriptCore 528+ (Nightly build) All All RESOLVED FIXED P2 Normal --- 128047 128057 128158 128162 128229 128234 128291 112840 132357 1 fpizlo fpizlo barraclough ggaren mark.lam mhahnenberg mmirman msaboff oliver sam oldest_to_newest 974578 0 fpizlo 2014-01-31 22:22:35 -0800 ... 974638 1 fpizlo 2014-02-01 11:34:15 -0800 Currently it appears that we jettison FTL-compiled code multiple times, for no apparent reason. That's dumb. We shouldn't do that. 974700 2 fpizlo 2014-02-01 20:43:49 -0800 It looks like two things are going wrong here: 1) The GC is collecting the main structure associated with GBEmu's state. 2) ToThis never realizes that it should stop speculating badly if the GC resets its structure. (2) is a progression for the FTL because it fixes the rage-recompilations, but it's a regression for the DFG because we lose out on GetById/PutById optimizations. The overspeculation on ToThis is the only thing that's giving us information about structures! It's pretty funny. 974717 3 fpizlo 2014-02-01 22:01:35 -0800 There appear to be at least two reasons why the GC is collecting the main structure: 1) On the first run of GBEmu, it adds a property called "secondaryBuffer", but doesn't add it in subsequent iterations. Interestingly, if we hadn't collected the structure, then everything would more-or-less work: we'd have a set of polymorphic GetByIds and PutByIds - but we know how to handle those. 2) Even if you hack the benchmark to always add "secondaryBuffer", the structure is still being collected. It's not clear exactly why, but there is clearly a second reason. The nightmare of all of this is making me have second thoughts about our handling of weak structures. It's true that the GC often saves us by telling us that a particular structure will never be used again. That's pretty cool. But it then also sometimes has us think that a heap access is entirely unoptimizable even though it became fine after a one-off clearing by GC. I still need to think more about this. 978749 4 fpizlo 2014-02-09 23:17:23 -0800 As of http://trac.webkit.org/changeset/163765, the FTL is a speed-up on gbemu even without any warm-up. That's pretty good. I'll keep this bug open because I think we can do even better. 1005125 5 fpizlo 2014-04-29 14:42:44 -0700 Our convergence is pretty good now.