RFR(S): 8189616: [s390] Remove definition and all uses of STCK instruction

Schmidt, Lutz lutz.schmidt at sap.com
Mon Oct 23 09:06:09 UTC 2017

Hi Martin,
thank you for your review!
Regards, Lutz

Dr. Lutz Schmidt | SAP JVM | PI  SAP CP Core | T: +49 (6227) 7-42834

On 23.10.2017, 10:36, "Doerr, Martin" <martin.doerr at sap.com<mailto:martin.doerr at sap.com>> wrote:

Hi Lutz,

looks good. I think there’s no reason for using stck since we have stckf, so I’m ok with it.
Thanks for removing the z900 code. We only support z10 and newer.

Best regards,

From: hotspot-compiler-dev [mailto:hotspot-compiler-dev-bounces at openjdk.java.net] On Behalf Of Schmidt, Lutz
Sent: Donnerstag, 19. Oktober 2017 10:11
To: hotspot-compiler-dev at openjdk.java.net
Subject: RFR(S): 8189616: [s390] Remove definition and all uses of STCK instruction

Dear all,

I would like to request reviews for this s390-only bug fix:

Bug:    https://bugs.openjdk.java.net/browse/JDK-8189616
Webrev: http://cr.openjdk.java.net/~lucy/webrevs/8189616.00/index.html

STCK is an ancient instruction to store a CPU timer value. It guarantees strict monotonicity of the stored values across all CPUs in a system. The inherent synchronization has a performance impact which becomes “considerable” (according to IBM specialists) with the recently announced processor generation (z14).

This change removes the STCK instruction from s390 platform code. The intent is to prevent inadvertent use of the instruction.

Thank you!

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