From: Vojtech Pavlik <vojtech@suse.cz>
To: Ingo Adlung <Ingo.Adlung@t-online.de>
Cc: linux-kernel@vger.kernel.org, Linus Torvalds <torvalds@transmeta.com>
Subject: Re: [PATCH 2/3] High-res-timers part 2 (x86 platform code) take 5.1
Date: Mon, 14 Oct 2002 09:18:56 +0200 [thread overview]
Message-ID: <20021014091855.A4197@ucw.cz> (raw)
In-Reply-To: <3DA94F07.7070109@t-online.de>; from Ingo.Adlung@t-online.de on Sun, Oct 13, 2002 at 12:46:31PM +0200
On Sun, Oct 13, 2002 at 12:46:31PM +0200, Ingo Adlung wrote:
> Linus Torvalds wrote:
> > On Wed, 9 Oct 2002, george anzinger wrote:
> >
> >>This patch, in conjunction with the "core" high-res-timers
> >>patch implements high resolution timers on the i386
> >>platforms.
> >
> >
> > I really don't get the notion of partial ticks, and quite frankly, this
> > isn't going into my tree until some major distribution kicks me in the
> > head and explains to me why the hell we have partial ticks instead of just
> > making the ticks shorter.
Not speaking for a major distro, just for me writing HPET (high
performance event timer ...) support for x86-64 (and it happens to exist
on ia64 as well, and possibly might be in new Intel P4 chipsets, too).
It's a very nice piece of hardware that allows very fine granularity
aperiodic interrupts (in each interrupt you set when the next one will
happen), without much overhead.
It'd be a shame to just set this timer to 1kHz periodic just use that as
a base timer, when you can do much better resolution and latency-wise.
HPET has a base clock > 10 MHz.
> > Linus
>
> In any kind of virtual environment you would rather prefer a completely
> tickless system alltogether than increased tick rates. In a S/390
> virtual machine, running many hundreds of virtual Linux servers the
> 100Hz timer pops are already considerably painful, and going to a higher
> tick rate achieving higher timer resolution is completely prohibitive.
> Similar is true in many embedded systems related to power consumption of
> high frequency ticks.
>
> However, George has shown that introducing the notion of a completely
> tickless system is expensive on Intel overhead wise, thus partial ticks
> seem to be a possibility addressing the needs for embedded and virtual
> environments, getting decent timer resolution as needed.
When HPET becomes a standard (yes, it's a MS requirement for new PCs),
it won't be expensive on i386 anymore.
--
Vojtech Pavlik
SuSE Labs
next prev parent reply other threads:[~2002-10-14 7:13 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-09 22:47 [PATCH 2/3] High-res-timers part 2 (x86 platform code) take 5.1 george anzinger
2002-10-09 23:14 ` Linus Torvalds
2002-10-09 23:42 ` george anzinger
2002-10-10 15:03 ` Eric W. Biederman
2002-10-10 15:45 ` george anzinger
2002-10-10 15:54 ` Oliver Xymoron
2002-10-10 16:24 ` george anzinger
2002-10-10 17:04 ` Oliver Xymoron
2002-10-10 17:47 ` george anzinger
2002-10-13 10:46 ` Ingo Adlung
2002-10-14 7:18 ` Vojtech Pavlik [this message]
2002-10-14 22:17 ` Pavel Machek
2002-10-15 7:13 ` Vojtech Pavlik
2002-10-15 21:45 ` george anzinger
2002-10-17 21:54 ` Randy.Dunlap
2002-10-17 22:11 ` Robert Love
2002-10-18 13:11 ` mbs
2002-10-10 0:50 Dan Kegel
2002-10-10 1:33 ` Ben Greear
2002-10-10 3:55 ` Jeff Dike
2002-10-10 3:32 ` Dan Kegel
2002-10-10 12:34 ` mbs
2002-10-12 22:03 Jim Houston
2002-10-14 6:50 ` Ulrich Windl
2002-10-15 22:03 ` george anzinger
2002-10-19 1:02 Brad Bozarth
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