On Apr 29, 2011, at 3:44 PM, Rémi Forax wrote: > On 04/29/2011 01:09 PM, Christian Thalinger wrote: >> On Apr 28, 2011, at 3:19 PM, Charles Oliver Nutter wrote: >>> On Thu, Apr 28, 2011 at 5:16 AM, Christian Thalinger >>> <christian.thalin...@oracle.com> wrote: >>>> I took a look at it. I used 64-bit x86 since the code is a bit smaller >>>> than with 32-bit. >>>> >>>> The code is almost identical but three things popped into my eye (the >>>> output is from PrintOptoAssembly): >>>> >>>> 1. The obvious one: the method handle call site guard: >>>> >>>> 1a4 B32: # B160 B33<- B31 B149 B123 Freq: 0.499969 >>>> 1a4 movq R10, byte[int:>=0]<ciObject ident=770 PERM >>>> address=0xe99088> * # ptr >>>> 1ae movq R10, [R10 + #1576 (32-bit)] # ptr >>>> 1b5 movq R11, [R10 + #32 (8-bit)] # ptr >>>> 1b9 movq R8, java/lang/invoke/AdapterMethodHandle:exact * # >>>> ptr >>>> 1c3 cmpq R11, R8 # ptr >>>> 1c6 jne,u B160 P=0.000000 C=-1.000000 >>> I saw in your other email that eliminating this puts indy on par with >>> dynopt, which is spectacular news. Can you elaborate on how that would >>> be possible to do "correctly" (as in not via a hack)? Would it be a >>> lighter-weight check and deopt of some kind (in Hotspot), or is it >>> something I'd need to rig up on my code? >> >> This would be what we referred to in the past as pull-vs-push notification. >> I don't have details about that yet but maybe John has already thought this >> through and has an implementation idea (or even details). Not sure when get >> around to implement that. > > The API for push notification is > MutableCallSite.syncAll/SwitchPoint.invalidateAll and is not currently > implemented in the RI. > The idea is that instead of using a guard to check if there is a meta > model change, the target of a callsite has > no guard for that but the runtime track all these callsites. > By example for a + callsite in JRuby, you only install a guard that > check if the current object is a Fixnum > using a getClass() identity check. If someone somewhere open the Fixnum > class to change something, > the runtime will change all callsites that use Fixnum to set their > targets to fallbacks that use > a slow path and then call MutableCallSite.syncAll on all these callsites. > syncAll ensures that only the new targets (the fallbacks) are visible > for the whole program. > > Instead of using syncAll you can use SwitchPoint.invalidateAll which > allow you to create > a special guard on a condition like is my meta model change or not. > This guard is not a real one because instead of doing the check each > time when it calls, > it does nothing but when the SwitchPoint is invalidated, the guard is > replaced by its fallback > doing a kind of deoptimization. > > Currently in the RI, SwitchPoint checks a volatile field instead of > doing the optimization/deoptimization. > I'm not far from having this working in the backport (I'm just stuck > with a memory model issue). > > So currently, the push API is here but there is no support from hotspot. > I guess we should to kill any people that will be between John and a > keyboard > until he implements MutableCallSite.syncAll.
There you go. I wasn't sure this SwitchPoint thing is related to that but thanks for clarifying it. -- Christian _______________________________________________ mlvm-dev mailing list mlvm-dev@openjdk.java.net http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev
