RFR: 8202711: Merge tiered compilation policies
vladimir.kozlov at oracle.com
Mon May 7 20:53:05 UTC 2018
On 5/7/18 12:59 PM, Claes Redestad wrote:
> 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
Agree, this is good reason for change.
>> 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?
I want to remove == 3 at all. Limit flag to 0,1,2 values. Where 2 is
default and only option for Tiered.
>> 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.
Yes, I totally agree with renaming.
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