TieredCompilation question

[Gilles Duboscq]

MC could get deoptimized and its invocation counter reset, so it's not safe
to assume that a method will not get recompiled just because it has already
been compiled by C2.
Whatever happens set_not_c1_compilable() should prevent any C1 compilation
or inlining, it could just get re-compiled by C2.

On Fri, Jan 11, 2013 at 5:47 PM, Tom Deneau <tom.deneau at amd.com> wrote:

>  I tried Method::set_dont_inline().  It was a little unclear whether that
> affected only C1 or both C1 and C2.  I like your suggestion better.****
>
> ** **
>
> Question: if MC had already been compiled as C2, I am assuming it would
> never then get compiled by C1, is that correct?****
>
> ** **
>
> -- Tom****
>
> ** **
>
> *From:* gilwooden at gmail.com [mailto:gilwooden at gmail.com] *On Behalf Of *Gilles
> Duboscq
> *Sent:* Friday, January 11, 2013 3:39 AM
> *To:* Deneau, Tom
> *Cc:* Vladimir Kozlov; sumatra-dev at openjdk.java.net
> *Subject:* Re: TieredCompilation question****
>
> ** **
>
> I rather think that even though inlining MC into MA may be slower than
> calling the C2-compiled MC, it should not matter too much since it's a
> transitory state.****
>
> In the end MA should be compiled using C2 and the assumption is that MC
> will get inlined in this compilation too. And anyway, if it does not then
> it would be back to calling the C2-compiled MC.****
>
> ** **
>
> If you want to avoid compilation of a method by C1 altogether you could
> try Method::set_not_c1_compilable() that way C1 would neither try to
> compile it or try to inline it.****
>
> ** **
>
> Gilles****
>
> ** **
>
> On Fri, Jan 11, 2013 at 5:31 AM, Deneau, Tom <tom.deneau at amd.com> wrote:**
> **
>
> So the assumption is that MC inlined into MA will be better than calling a
> C2-compiled version of MC?
>
> I suppose it is also possible to forbid inlining of MC, so it would have
> to call the compiled version?
>
> -- Tom****
>
>
>
> -----Original Message-----
> From: sumatra-dev-bounces at openjdk.java.net [mailto:
> sumatra-dev-bounces at openjdk.java.net] On Behalf Of Vladimir Kozlov
> Sent: Thursday, January 10, 2013 7:59 PM
> To: sumatra-dev at openjdk.java.net
> Subject: Re: TieredCompilation question
>
> You step on your own mine :)
>
> Yes, it has such pathology for inlined by C1 methods. The assumption is
> that when C2 will compile MA it will also inline MB and MC. You can try
> to lower Tier4CompileThreshold.
>
> Vladimir
>
> On 1/10/13 5:22 PM, Deneau, Tom wrote:
> > I will display my ignorance of TieredCompilation here. :)
> > I think I am seeing the following but I am not positive...
> >
> > Let's say method MA calls MB calls MC.
> > MC gets compiled at C2 level.
> > Everything works well and the MC method compiled at C2 gets called
> several hundred times.
> >
> > Now method MA gets compiled at level 3 in C1.
> > This C1 compilation of MA decides to inline MB and then MC into its C1
> compilation.
> > So it no longer uses the C2 compilation of MC??
> >
> > In my particular case MC had called some intrinsic routines which were
> only defined as intrinsics in C2.
> > So the net effect of being compiled at C1 when it was inlined into MA
> was that we lose those intrinsics.
> >
> > Is this how TieredCompilation is supposed to  work?
> >
> > I should add here that the early compilation of MC at C2 level was in my
> case artificially forced by some code I added to Hotspot (so I might have
> missed something in setting that up).
> >
> > With Tiered off, this all worked nicely of course.
> >
> > -- Tom
> >
>
> ****
>
> ** **
>