JDK10/RFR(L): 8172231: SPARC ISA/CPU feature detection is broken/insufficient (on Solaris).

[David Holmes]

Hi Patric,

I have read the below and looked through the proposed changes. While I 
can't validate the details (as I am not familiar with chip capabilities) 
the overall approach looks good and I prefer the capability-based tests 
to the "family" based tests.

As you note there are a few fixme's and follow ups to do, but one 
suggestion I have is to remove the UseV8InstrsOnly flag. It doesn't make 
sense to me to keep this if we will abort on V8 anyway. The nature of 
the flag, in an unsupported environment, precludes it from following our 
more usual deprecation process, and it is a develop flag anyway.

I do have concerns about how this may work on Fujitsu, but hopefully 
there is plenty of bake-time in JDK 10 to shake out any issue.

Thanks,
David

On 28/04/2017 11:48 PM, Patric Hedlin wrote:
> Dear all,
>
> I would like to ask for help to review the following change/update:
>
> Issue: https://bugs.openjdk.java.net/browse/JDK-8172231
>
> Webrev: http://cr.openjdk.java.net/~neliasso/8172231/
>
>
>
> 8172231: SPARC ISA/CPU feature detection is broken/insufficient (on
> Solaris).
>
>     Updating SPARC feature/capability detection (incorporating changes
> from Martin Walsh).
>     More complete set of features as provided by 'getisax(2)' interface,
> propagated via JVMCI.
>     More robust hardware probing for additional features (up to Core S4).
>     Removing support for old, pre Niagara, hardware.
>     Removing support for old, pre 11.1, Solaris.
>
>     Changed behaviour:
>     Changing SPARC setup for AllocatePrefetchLines and
> AllocateInstancePrefetchLines
>     such that they will (still) be doubled when cache-line size is small
> (32 bytes),
>     but more moderately increased on new/contemporary hardware (inc >=
> 50%).
>     Changing to default instruction fetch alignment based on derived
> caps. instead
>     of relying on default/configuration values.
>
>     The above changes also subsumes:
>     8035146: assert(is_T_family(features) == is_niagara(features),
> "Niagara should be T series") is incorrect
>     8054979: Remove unnecessary defines in SPARC's
> VM_Version::platform_features
>
>
> Rationale:
>
>     Current hardware detection on Solaris/SPARC is not up to date with
> the "latest" (here,
>     meaning commercially available server solutions, i.e. T7/M7). To
> facilitate improved
>     use of the new hardware features provided (by Core S3&S4) these
> capabilities need to
>     be recognised by the JVM.
>
>     NOTE: This update is limited to Core S3&S4, i.e. not including Core
> S5. Proper Core S5
>     support will be added when regular testing and benchmarking
> resources are available,
>     i.e. regular testing need to include M8 hardware.
>
>
> Caveat:
>
>     This update will introduce some redundancies into the code base,
> features and definitions
>     currently not used, as well as a (small) number of FIXMEs, addressed
> by subsequent bug or
>     feature updates/patches. Fujitsu HW is treated very conservatively.
>
>
> Testing:
>
>     Mostly tested on JDK9 (RBT/hotspot/comp). Only local testing on
> JDK10 (jtreg/hotspot).
>
>
> Benchmarking:
>
>     Benchmark reports from a limited set of runs can be found at:
>
>
> http://aurora.se.oracle.com/performance/reporting/report/patric.hedlin.TvM.jbb05
>
>
>
> http://aurora.se.oracle.com/performance/reporting/report/patric.hedlin.TvM.jvm08
>
>
>
> http://aurora.se.oracle.com/performance/reporting/report/patric.hedlin.TvM.octane.plus
>
>
>
>     (Limited availability of M7 hardware prevents complete suites/runs.)
>
>
> Best regards,
> Patric
>