vm.pmap.pcid_enabled="0" seems to eliminate Java/Jenkins crashing problems in FBSD 10

[Craig Rodrigues]

On Fri, Feb 21, 2014 at 2:54 PM, Attilio Rao <attilio at freebsd.org> wrote:

> On Thu, Feb 20, 2014 at 5:45 AM, Craig Rodrigues <rodrigc at freebsd.org>
> wrote:
> > Hi,
> >
> > I am followed Jung-uk Kim's advice here:
> >
> >
> http://lists.freebsd.org/pipermail/freebsd-java/2014-February/010582.html
> >
> >
> > and configured the one of the FreeBSD stable/10 VM's (running at r261732)
> > that I have running
> > under BHyve with the
> > following in /boot/loader.conf:
> >
> > vm.pmap.pcid_enabled="0"
>
> IIRC PCID had to be already disabled by default as we saw it was
> slower in the real world or I'm missing something?
>
> Thanks,
> Attilio
>


I never observed an problems with speed problems being introduced by
vm.pmap.pcid_enabled="1".
All I can say is that I saw that Java VM crash when
vm.pmap.pcid_enabled="1", but setting
vm.pmap.pcid_enabled="0" stopped the crashes with the Java VM.

My focus was on stopping the Java crashes.

I still don't know the real cause of the problem...is it:

(1)  problem with new code that is executed when vm.pmap.pcid_enabled="1"
implementation?
(2)  latent bug in VM that is triggered by vm.pmap.pcid_enabled="1" but not
directly related to that?
(3)  bug in OpenJDK?

Hard to say for sure, but any help from a FreeBSD VM expert would be
greatly appreciated.

--
Craig