Re: git: 3d9d64aa1846 - main - kern_tc: unify timecounter to bintime delta conversion

On Tue, Nov 30, 2021 at 11:08 AM Andriy Gapon <avg@freebsd.org> wrote:
>
> On 30/11/2021 18:14, Kyle Evans wrote:
> > I wonder if this helps explain the behavior we saw when enabling TSC
> > on VirtualBox guests. Threads doing small ~1 second or less sleeps
> > would start to miss their wakeups, so we'd consistently see, e.g.,
> > shutdown issues after applying a high loading while we're waiting for
> > bufdaemon threads.
>
> It very well may be the case.
> The reason I arrived at this change is that we also sometimes saw the same
> problem but on VMWware.  That prompted me to add some diagnostic code to
> sleepqueue to turn those missed wakeups into panics.
>
> As kib pointed out, mav recently made a change that would mask the problem as a
> side effect:
> https://cgit.FreeBSD.org/src/commit/?id=6df1359e5542f69179c142be1ea099d447e273d1
> But I wanted to fix the root cause anyway.
>

Ok, cool, thanks!

I'll do some re-testing under VirtualBox and see if we can just revert
this entirely: https://cgit.freebsd.org/src/commit/sys/x86/x86/tsc.c?id=8cc15b0dfc2f3299

Thanks,

Kyle Evans