One thing that would be very useful (and I've asked Vladimir Kozlov for it) is to expose a product flag (I believe there's one now but it's develop) to trace EA decisions/reasons. Maybe that's already planned, but if not, hopefully it makes it at some point.
Sent from my phone On Jan 25, 2014 5:15 AM, "Remi Forax" <fo...@univ-mlv.fr> wrote: > On 01/24/2014 11:01 PM, Vitaly Davidovich wrote: > >> This would be predicated on escape analysis, whose effectiveness is in >> turn >> driven by sufficient inlining whereby compiler can see that instance >> doesn't escape. Inlining, in turn, can be screwed up by (amongst other >> things) polymorphic call sites. So in the end, it's all quite brittle and >> sensitive :). Personally, in places where it matters, I try to allocate >> as >> little as possible explicitly - a lot of times much more effective than >> hoping compiler helps out and/or turning GC knobs. >> >> Sent from my phone >> > > Hi Andrej, > if you see a lot of instances of ArrayList iterator it means that you have > a code path that create an iterator and use it later and the JIT is not > able to see the creation and the use in the same inlining horizon. As > Vitaly said, it's perhaps because you have the same code called with > several different kinds of List (teach your programmer to stop to use > LinkedList :) or because the code create an Iterator too far from where you > use it (by example if the iterator is stored in a List or a Map). > > If you use -XX:+PrintInlining, the VM will print the reason why something > is not inlined. > > cheers, > Rémi > > > On Jan 24, 2014 4:36 PM, "Andrej Golovnin" <golov...@gmx.net> wrote: >> >> Hi Rémi, >>> >>> With latest jdk8, it's not true anymore. >>>> (and most of the time the iterator object is not created anymore at >>>> >>> least with jdk7+). >>> >>> Could you please explain it a little bit more? When is that optimization >>> applied, >>> e.g. what conditions are required for this optimization, since which >>> version >>> of JDK/Hotspot it is supported, where it is implemented in JDK? >>> >>> When I take look at a product I'm working on, I see a lot instances of >>> ArrayList$Itr objects, >>> which are created by for-each loops (we use JDK 7u51). >>> >>> Thanks in advance! >>> >>> Best regards, >>> Andrej Golovnin >>> >>> >>> >>> >
