From: Dan Kegel <dank@kegel.com>
To: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] High-res-timers part 2 (x86 platform code) take 5.1
Date: Wed, 09 Oct 2002 17:50:30 -0700 [thread overview]
Message-ID: <3DA4CED6.1BD30A2F@kegel.com> (raw)
george anzinger wrote:
> Linus Torvalds wrote:
> > 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.
> ...
>
> Making ticks shorter causes extra overhead ALL the time,
> even when it is not needed. Higher resolution is not free
> in any case, but it is much closer to free with this patch
> than by increasing HZ (which, of course, can still be
> done). Overhead wise and resolution wise, for timers, we
> would be better off with a 1/HZ tick and the "on demand"
> high-res interrupts this patch introduces.
Seems reasonable to me. Increasing HZ adds overhead -
it makes sense to incur the interrupt overhead only when it's
needed. In my case, we want to provide fairly precise
network delays (we're doing a WAN simulator), and still hit
line rate. Now, I'm way far from the code, but I suspect that
the interrupt overhead needed to get the precision the customer
is calling for would be totally prohibitive. I dunno if we'll
get the precision the customer wants with George's approach,
but we'll get a lot closer than we would setting HZ to 10000
on our wimpy little embedded platform.
George's approach would work a lot better when doing lots of UML VM's
on a single box, too, wouldn't it?
- Dan
next reply other threads:[~2002-10-10 0:33 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-10 0:50 Dan Kegel [this message]
2002-10-10 1:33 ` [PATCH 2/3] High-res-timers part 2 (x86 platform code) take 5.1 Ben Greear
2002-10-10 3:55 ` Jeff Dike
2002-10-10 3:32 ` Dan Kegel
2002-10-10 12:34 ` mbs
-- strict thread matches above, loose matches on Subject: below --
2002-10-19 1:02 Brad Bozarth
2002-10-12 22:03 Jim Houston
2002-10-14 6:50 ` Ulrich Windl
2002-10-15 22:03 ` george anzinger
2002-10-09 22:47 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
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
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