Re: timekeeping regression?

[Brad Spencer <brad%anduin.eldar.org@localhost>]

"Mathew, Cherry G.*" <c%bow.st@localhost> writes:

>>>>>> Brad Spencer <brad%anduin.eldar.org@localhost> writes:
>
>     > "Greg A. Woods" <woods%planix.ca@localhost> writes:
>     >> 
>     >> At Wed, 20 Mar 2024 03:31:00 +0000, "Mathew, Cherry G.*" <c%bow.st@localhost> wrote:
>     >> Subject: Re: timekeeping regression?
>     >>> 
>     >>> I think the problem here is that there's no clarity in the API
>     >>> about ownership. So we'll probably need to have a look at what
>     >>> linux and/or FreeBSD does, to understand what the current
>     >>> consensus is - this seems to be the linux way of documentation -
>     >>> a sort of mob rules situation.
>     >> 
>     >> Hmmm...  FreeBSD (14.0) is now the only domU system I have that's
>     >> been keeping time properly, even with the dom0 running on one
>     >> pinned CPU.
>     >> 
>     >> All the NetBSD systems have experienced large time drifts after
>     >> about 7 days of uptime.
>     >> 
>     >> So, yeah, FreeBSD is doing something right/better!
>     >> 
>     >> -- Greg A. Woods <gwoods%acm.org@localhost>
>     >> 
>     >> Kelowna, BC +1 250 762-7675 RoboHack <woods%robohack.ca@localhost> Planix,
>     >> Inc. <woods%planix.com@localhost> Avoncote Farms <woods%avoncote.ca@localhost>
>     >> 
>
>
>     > I have lost track... is your FreeBSD domain a pure PVH or a normal
>     > PV or PVSHIM??  All of my multi-vcpu pure PVH guests can keep time
>     > pretty well, but nearly all multi-vcpu PV guest (pure PV or
>     > PVSHIM) will tend to lose their minds after a while, although not
>     > in the same way you have been describing.  
>
> Can you confirm that you see this only on PV/PVSHIM ?

For me personally, I only have problems with PV/PVSHIM guests and only
if they are using more than one vcpu.  The PVH guests appear to be fine.
But to mention again, I don't have the same problem as Greg.  In my
case, the monotonic clock goes backwards, but the guest can keep time
sync just fine with ntpd or chronyd until that event.

> Also, do you see this on any other OS (I believe linux still has the
> ability to run pure PV ?).

I don't run any other OS other than NetBSD in pure PV or PVHIM mode.
Support for pure PV guests was removed from Linux and the versions I run
are too new to support anything but PVH, which is what they use
(ArchLinux, in particular).





-- 
Brad Spencer - brad%anduin.eldar.org@localhost - KC8VKS - http://anduin.eldar.org