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

Patric Hedlin patric.hedlin at oracle.com
Thu Jun 15 16:03:15 UTC 2017

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/phedlin/tr8172231/

This is review #2.

Thanks to Stefan Anzinger <stefan.anzinger at oracle.com>
           David Holmes    <david.holmes at oracle.com> -> follow-up in 
           Vladimir Kozlov <vladimir.kozlov at oracle.com> -> follow-up in 
for reviewing the previous version.

Slight change after review #1 (agreed with Vladimir Kozlov):

     Revoked instruction fetch alignment based on derived caps. (gain is 
small on
     T4 and T7/M7 even for perfectly slotted bundles, and absent on M8).

8172231: SPARC ISA/CPU feature detection is broken/insufficient (on 

     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 
     such that they will (still) be doubled when cache-line size is 
small (32 bytes),
     but more moderately increased on new/contemporary hardware (inc >= 

     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 


     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.


     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.


     Mostly tested on JDK9 (jtreg/RBT/hotspot/tier0-comp).
     Testing on JDK10 (jtreg/RBT/hotspot/precheckin-comp).


     No additional benchmarking results produced (since previous review).

Best regards,

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