From: Vojtech Pavlik <vojtech@suse.cz>
To: Pavel Machek <pavel@suse.cz>
Cc: Vojtech Pavlik <vojtech@suse.cz>,
Ingo Adlung <Ingo.Adlung@t-online.de>,
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: Tue, 15 Oct 2002 09:13:58 +0200 [thread overview]
Message-ID: <20021015091358.A3969@ucw.cz> (raw)
In-Reply-To: <20021015001747.A661@elf.ucw.cz>; from pavel@suse.cz on Tue, Oct 15, 2002 at 12:17:47AM +0200
On Tue, Oct 15, 2002 at 12:17:47AM +0200, Pavel Machek wrote:
> Hi!
>
> > > >>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.
>
> I believe the problem is like this: assume you have three timers,
> 10msec polling of mouse, 30msec keyboard autorepeat and 50msec cursor
> blinking. With current approach, you get
>
> 10msec userland runs
> <enter kernel>
> <process mouse>
> <process keyboard>
> <process cursor>
> <exit kernel>
>
> With hires timers, you get:
>
> 3msec userland runs
> <enter kernel>
> <process mouse>
> <exit kernel>
> 2msec userland runs
> <enter kernel>
> <process keyboard>
> <exit kernel>
> ...
>
> which is not so efficient. I guess rounding could be implemented to
> preserve this "do-all-together" ability?
Actually that's exactly why you'd want sub-tick timing. For timers where
you don't care too much about the timing ;) you could do the rounding,
and for those where you need exact timing (sound, video, ...) you could
call a different add_timer() which would disable the coalescing.
--
Vojtech Pavlik
SuSE Labs
next prev parent reply other threads:[~2002-10-15 7:08 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
2002-10-14 22:17 ` Pavel Machek
2002-10-15 7:13 ` Vojtech Pavlik [this message]
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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