A few brief observations based on stepping through the problem area in the debugger:
- The generated code for this JS function calls directly into Builtins_LoadICTrampoline_Megamorphic. - However, the feedback vector slot for that load is in monomorphic state. - The map we're currently loading from matches the map in the feedback vector. - We don't find the relevant data in the global megamorphic lookup cache. - UpdatePolymorphicIC returns true, so IC::SetCache returns without running UpdateMegamorphicCache, so this property lookup never has any chance to get faster. Does anybody have advice about how a LoadIC could initially get into this state where its feedback says monomorphic but the generated code is executing a megamorphic load? On Monday, July 27, 2020 at 12:44:59 AM UTC-7, Camillo Bruni wrote: > > Hi, > > Inline Caches are a crucial optimization > <https://en.wikipedia.org/wiki/Inline_caching> to speed up > property accesses. > Usually, you get misses the first time an inline cache is used (for > initialization) or when the shape of objects is different (different order, > different types of properties). > > Spending 55% of your time in LoadIC_Miss seems really high. Without access > to the repro this is hard to assess. > > cheers, > Camillo > > On Sat, 25 Jul 2020 at 21:12, Wayakorn Vadhanasin <waya...@gmail.com > <javascript:>> wrote: > >> I am working on updating my Electron app from Electron 4 (Chromium 69) to >> Electron 8 (Chromium 80). I am occasionally experiencing random delays in >> my app while calling a JS function to process HTML DOMs (no external >> callouts). >> >> Looking closely at the profiling data collected from the Windows >> Performance Analysis tool, I am seeing the following calls during the repro: >> >> * v8::internal::Runtime_LoadIC_Miss* - 55% >> * v8::internal::LoadIC::Load *- 13% >> >> More details on the LoadIC_Miss: >> v8::internal::IC::UpdatePolymorphicIC >> v8::internal::IC::SetCache >> v8::internal::LoadIC::UpdateCaches >> v8::internal::LoadIC::Load >> v8::internal::Runtime_LoadIC_Miss >> >> Very few instances of the above occurred in a normal condition, only when >> there was a perf issue. >> >> I'd like to understand more what inline cache is doing. Have there been >> many churns in this area since Chromium 69? Any hints or suggestions on the >> next step of investigation is appreciated. Thanks in advance. >> >> Way >> >> >> >> >> -- >> -- >> v8-users mailing list >> v8-u...@googlegroups.com <javascript:> >> http://groups.google.com/group/v8-users >> --- >> You received this message because you are subscribed to the Google Groups >> "v8-users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to v8-u...@googlegroups.com <javascript:>. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/v8-users/ad7fe487-be79-491a-96ee-37c286274c12n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/v8-users/ad7fe487-be79-491a-96ee-37c286274c12n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- -- v8-users mailing list v8-users@googlegroups.com http://groups.google.com/group/v8-users --- You received this message because you are subscribed to the Google Groups "v8-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to v8-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/v8-users/c84c9a81-6b53-4339-ad55-e803ecea51cco%40googlegroups.com.
