RFR: 8202711: Merge tiered compilation policies

[Claes Redestad]

Hi Vladimir,

On 2018-05-07 21:25, Vladimir Kozlov wrote:
> Hi Claes,
>
> First, please explain why tiered compilation policies "should be 
> merged into a single policy"?

so, from my understanding these two different tiered compilation 
policies stem from a time when
TieredCompilation (briefly) had a closed, commercial feature set, where 
most (all?) tuning work
went into the advanced (closed source) policy, which then quickly became 
the default once it was
all open sourced.

Using the simple compilation policy explicitly 
(-XX:CompilationPolicyChoice=2, almost as obvious
as -XX:SyncKnobs...) has barely any testing coverage, is highly likely 
to be bit rot and buggy and
not something we've tuned or benchmarked for in a long while. 
Effectively this deprecates/obsoletes
the specific choice, which doesn't seem to be documented anywhere but in 
code, but does so
gracefully.

>
> After these changes there is no difference between 
> CompilationPolicyChoice 2 and 3. Why you kept both?

Would you prefer if the CompilationPolicyChoice == 2 case did an 
Unimplemented() as if TIERED
wasn't defined in the build?

>
> Changes looks good but I wish all compilation policy files moved into 
> hostpot/share/compiler directory. But it could be done separately 
> otherwise current review will be difficult.

Right, renaming and moving this is easier to do separately as a 
follow-up. Perhaps runtime folks
have opinions..? Can I move memory/heap.c|hpp files to 
share/compiler/codeHeap.c|hpp, too? ;-)

As mentioned I'd like to see this renamed to TieredCompilationPolicy (or 
similar) since the
simple-/advanced notation is as unclear as they come and has led many 
(myself included) astray.

> Good.

Thanks!

/Claes