RFR: 8241603: ZGC: java/lang/management/MemoryMXBean/MemoryTestZGC.sh crashes on macOS

[Per Liden]

Thanks! Just checking, are you testing without the workaround[1] you did 
to your VMware instances?

cheers,
Per

[1] "We solved our issue by reconfiguring the VMWare VM to have no 
hyperthreading and have the CPUs pinned to the VM. This solved the 
issues for us." - 
https://bugs.openjdk.java.net/browse/JDK-8241603?focusedCommentId=14327438&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14327438


On 4/7/20 12:07 PM, Baesken, Matthias wrote:
> Hi Per , I put your patch  into our  build/test queue .
> 
> Best regards, Matthias
> 
> 
> -----Original Message-----
> From: Per Liden <per.liden at oracle.com>
> Sent: Montag, 6. April 2020 17:04
> To: hotspot-gc-dev <hotspot-gc-dev at openjdk.java.net>; Langer, Christoph <christoph.langer at sap.com>; Baesken, Matthias <matthias.baesken at sap.com>; Zeller, Arno <arno.zeller at sap.com>
> Subject: RFR: 8241603: ZGC: java/lang/management/MemoryMXBean/MemoryTestZGC.sh crashes on macOS
> 
> It was reported that "Every few days, the test
> java/lang/management/MemoryMXBean/MemoryTestZGC.sh crashes on macOS. It
> is macOS 10.14.4, and it is a virtualized machine running with VMWare
> hypervisor."
> 
> The problem seems to be that the hypervisor (in some configurations) can
> migrate a "virtual CPU" from one physical CPU to another, and start to
> report a different APIC id. As a result, it can appear as if there are
> more than os:processor_count() CPUs in the system. To void this, we
> allow more than one APIC id to be mapped to the same logical processor
> id, so that os::processor_id() always returns a processor id that is
> less than os::processos_count().
> 
> One could argue that this is really a hypervisor bug, but we can still
> make an effort to mitigate the problem in the JVM.
> 
> SAP-folks (CC:ing those who commented in the bug), since you ran into
> this problem and I don't have access to a VMware setup where I can
> test/reproduce this, could you please test this patch to verify it
> solves the problem? If so, that would be much appreciated.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8241603
> Webrev: http://cr.openjdk.java.net/~pliden/8241603/webrev.0
> Testing: Tier 1-6 on macOS (but not macOS on top of VMware)
> 
> cheers,
> Per
>