From owner-freebsd-arch  Fri Oct 26 15:16: 6 2001
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To: Matthew Dillon <dillon@apollo.backplane.com>
Cc: Poul-Henning Kamp <phk@critter.freebsd.dk>,
	John Baldwin <jhb@FreeBSD.ORG>, arch@FreeBSD.ORG,
	Peter Wemm <peter@wemm.org>, Bakul Shah <bakul@bitblocks.com>
Subject: Re: 64 bit times revisited.. 
In-Reply-To: Message from Matthew Dillon <dillon@apollo.backplane.com> 
   of "Fri, 26 Oct 2001 15:09:48 PDT." <200110262209.f9QM9m739133@apollo.backplane.com> 
Date: Fri, 26 Oct 2001 15:28:35 -0700
From: Mike Smith <msmith@freebsd.org>
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> 
> :>    Before this gets misinterpreted, the 'ticks' I am talking about is 
> :>    not the kernel timer interrupt ticks... it's the high resolution cpu
> :>    or 825x ticks we get.  e.g. frequency dependant on the timer we use.
> :
> :Matt, that is the mess Linux is fighting with.  We have had a superior
> :solution for years by now which even allows us to change timekeeping
> :hardware on the fly as we find more suitable timebases.
> 
>     I don't consider our solution to be superior, I consider it to be a
>     huge mess.  It's a huge hack to deal with i386-specific time counter
>     issues and, frankly, it doesn't even do that good a job at it.

Actually, this isn't true at all.  It's a fairly neat solution to the
requirement that we have largely MI timekeeping.

>     We've
>     been plagued by backwards-time notifications and weird things happening
>     for YEARS now.

This is a combination if implementation issues and flat-out broken hardware.

>     It is far too sensitive to environmental conditions
>     like laptops going into sleep mode and such.  One unbelievably large
>     mess.

Again, these are implementation issues, and shouldn't be confused with
the basic design which is actually quite sound.


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