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List: freebsd-commits-all
Subject: Re: cvs commit: src/sys/sparc64/sparc64 machdep.c
From: Marius Strobl <marius () alchemy ! franken ! de>
Date: 2004-09-30 19:40:21
Message-ID: 20040930214021.A84755 () newtrinity ! zeist ! de
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On Thu, Sep 30, 2004 at 03:24:43PM -0400, Ken Smith wrote:
> On Thu, Sep 30, 2004 at 09:09:27PM +0200, Poul-Henning Kamp wrote:
> > In message <200409301438.i8UEcx89022771@repoman.freebsd.org>, Ken Smith writes:
> > >kensmith 2004-09-30 14:38:59 UTC
> > >
> > > FreeBSD src repository
> > >
> > > Modified files:
> > > sys/sparc64/sparc64 machdep.c
> > > Log:
> > > This along with v1.6 of counter.c fixes some timecounter issues on
> > > MP machines (hopefully). CPU timers are OK on UP machines but we
> > > don't keep the timers in sync on MP machines so if the CPU's timer
> > > is chosen as the primary timecounter it's possible for time to
> > > not be monotonically increasing because different CPU's counters
> > > may be used at different times. But the CPU's counters are otherwise
> > > one of the higher quality counters available. So, on UP machines
> > > we'll use a relatively high quality value but on MP machines we'll
> > > use a quality that should prevent the CPU's counters from being chosen.
> >
> > The 'microsecond clock' is present in all suns so we don't leave any
> > machines without timecounters, right ?
> >
>
> Funny you should ask. Testing the first version of this patch was how
> we found the bug in counter.c - the machine I booted the test kernel
> with happened to decide the counter-timer wasn't suitable either due
> to the bug and it came up with no timecounters. You should see what
> happens to a machine that's not keeping time. :-)
>
> Marius has device maps for virtually all known Sparc hardware and
> he said all of the MP machines do have the counter-timer available
Well, that's an exaggeration :)
But I think I have enough to say that all Sun UltraSparc II boards
have a counter-timer device.
> in them. Only the IIi and IIe processor based systems don't and
> they're only UP machines.
>
> We are drastically low on timecounter-capable devices on sparc64
> though, it seems the counter-timer and the CPU are about all there
> is.
>
> If this makes you nervous and if you have any suggestions I'm all
> ears.
>
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