From: Pavel Machek <pavel@suse.cz>
To: Con Kolivas <kernel@kolivas.org>
Cc: Andrea Arcangeli <andrea@suse.de>, linux-kernel@vger.kernel.org
Subject: Re: dynamic-hz
Date: Mon, 13 Dec 2004 00:42:56 +0100 [thread overview]
Message-ID: <20041212234256.GK6272@elf.ucw.cz> (raw)
In-Reply-To: <41BCD5F3.80401@kolivas.org>
Hi!
> >The overhead is a single l1 cacheline in the paths manipulating HZ
> >(rather than having an immediate value hardcoded in the asm, it reads it
> >from a memory location not in the icache). Plus there are some
> >conversion routines in the USER_HZ usages. It's not a measurable
> >difference.
>
> Just being devils advocate here...
>
> I had variable Hz in my tree for a while and found there was one
> solitary purpose to setting Hz to 100; to silence cheap capacitors.
>
> The rest of my users that were setting Hz to 100 for so-called
> performance gains were doing so under the false impression that cpu
> usage was lower simply because of the woefully inaccurate cpu usage
> calcuation at 100Hz.
>
> The performance benefit, if any, is often lost in noise during
> benchmarks and when there, is less than 1%. So I was wondering if you
> had some specific advantage in mind for this patch? Is there some
> arch-specific advantage? I can certainly envision disadvantages to lower Hz.
Actually, I measured about 1W power savings with HZ=100. That's about
as much as spindown of disk saves...
Pavel
--
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!
next prev parent reply other threads:[~2004-12-12 23:49 UTC|newest]
Thread overview: 126+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-11 14:23 dynamic-hz Andrea Arcangeli
2004-12-11 14:50 ` dynamic-hz Zwane Mwaikambo
2004-12-12 6:57 ` dynamic-hz Andrea Arcangeli
2004-12-11 21:41 ` dynamic-hz Jan Engelhardt
2004-12-12 16:35 ` dynamic-hz Pavel Machek
2004-12-12 22:23 ` dynamic-hz Andrea Arcangeli
2004-12-12 23:36 ` dynamic-hz Con Kolivas
2004-12-12 23:42 ` Pavel Machek [this message]
2004-12-13 0:09 ` dynamic-hz Con Kolivas
2004-12-13 8:37 ` dynamic-hz Jan Engelhardt
2004-12-13 10:43 ` dynamic-hz Pavel Machek
2004-12-13 11:08 ` dynamic-hz Andrea Arcangeli
2004-12-13 19:36 ` dynamic-hz john stultz
2004-12-12 23:43 ` dynamic-hz Andrea Arcangeli
2004-12-13 0:18 ` dynamic-hz Con Kolivas
2004-12-13 0:27 ` dynamic-hz Andrea Arcangeli
2004-12-13 1:50 ` dynamic-hz Zwane Mwaikambo
2004-12-13 11:28 ` dynamic-hz Andrea Arcangeli
2004-12-13 12:43 ` dynamic-hz Pavel Machek
2004-12-13 12:58 ` dynamic-hz Andrea Arcangeli
2004-12-13 19:12 ` dynamic-hz Pavel Machek
2004-12-13 20:34 ` dynamic-hz john stultz
2004-12-13 20:49 ` dynamic-hz Pavel Machek
2004-12-14 2:04 ` dynamic-hz Andrea Arcangeli
[not found] ` <20041214013924.GB14617@atomide.com>
2004-12-14 9:37 ` dynamic-hz Pavel Machek
2004-12-14 21:18 ` dynamic-hz Tony Lindgren
2004-12-14 22:06 ` dynamic-hz Pavel Machek
2004-12-14 23:00 ` dynamic-hz linux-os
2004-12-14 23:13 ` dynamic-hz Tony Lindgren
2004-12-22 20:02 ` dynamic-hz Tony Lindgren
2004-12-14 23:04 ` dynamic-hz Tony Lindgren
2004-12-14 2:46 ` dynamic-hz Andrea Arcangeli
2004-12-14 19:24 ` dynamic-hz john stultz
2004-12-14 2:36 ` dynamic-hz Andrea Arcangeli
2004-12-14 9:39 ` dynamic-hz Pavel Machek
2004-12-14 9:59 ` dynamic-hz Pavel Machek
2004-12-14 15:25 ` dynamic-hz Andrea Arcangeli
2004-12-14 22:02 ` USB making time drift [was Re: dynamic-hz] Pavel Machek
2004-12-14 23:16 ` Andrea Arcangeli
2004-12-15 2:59 ` Gene Heskett
2004-12-15 9:17 ` Andrea Arcangeli
2004-12-15 16:44 ` Gene Heskett
2004-12-15 18:20 ` Andrea Arcangeli
2004-12-16 1:59 ` Gene Heskett
2004-12-16 11:30 ` Andrea Arcangeli
2004-12-16 12:50 ` Alan Cox
2004-12-15 20:16 ` Pavel Machek
2004-12-16 2:02 ` Gene Heskett
2004-12-15 17:03 ` Gene Heskett
2004-12-15 17:48 ` Tim Schmielau
2004-12-16 2:03 ` Gene Heskett
2004-12-16 0:58 ` Pavel Machek
2004-12-16 2:33 ` john stultz
2004-12-16 1:15 ` Time goes crazy in 2.6.9 after long cli [was Re: USB making time drift] Pavel Machek
2004-12-16 11:13 ` Andrea Arcangeli
2004-12-16 12:49 ` Alan Cox
2004-12-13 14:50 ` dynamic-hz Zwane Mwaikambo
2004-12-13 7:43 ` dynamic-hz Stefan Seyfried
2004-12-13 13:58 ` dynamic-hz Russell King
2004-12-13 14:14 ` dynamic-hz Russell King
2004-12-13 14:52 ` dynamic-hz Alan Cox
2004-12-13 16:23 ` dynamic-hz Russell King
2004-12-13 17:53 ` dynamic-hz Michael Buesch
2004-12-13 18:04 ` dynamic-hz Russell King
2004-12-13 19:04 ` dynamic-hz Pavel Machek
2004-12-13 20:11 ` dynamic-hz Russell King
2004-12-14 0:16 ` dynamic-hz Eric St-Laurent
2004-12-15 18:04 ` dynamic-hz Alan Cox
2004-12-15 19:54 ` dynamic-hz linux-os
2004-12-16 2:17 ` dynamic-hz Gene Heskett
2004-12-16 12:42 ` dynamic-hz linux-os
2004-12-17 20:12 ` dynamic-hz H. Peter Anvin
2004-12-16 9:10 ` dynamic-hz Gabriel Paubert
2004-12-16 12:17 ` dynamic-hz Geert Uytterhoeven
2004-12-16 14:00 ` dynamic-hz Mitchell Blank Jr
2004-12-13 15:30 ` dynamic-hz Zwane Mwaikambo
2004-12-13 15:59 ` dynamic-hz Russell King
2004-12-13 16:14 ` dynamic-hz Pavel Machek
2004-12-13 16:06 ` dynamic-hz Pavel Machek
2004-12-13 16:19 ` dynamic-hz Jan Engelhardt
2004-12-13 8:29 ` dynamic-hz Jan Engelhardt
2004-12-14 22:54 ` dynamic-hz Lee Revell
2004-12-14 23:38 ` dynamic-hz Chris Friesen
2004-12-15 8:32 ` dynamic-hz Jan Engelhardt
2004-12-13 11:02 ` dynamic-hz Andrew Morton
2004-12-13 11:17 ` dynamic-hz Andrea Arcangeli
2004-12-13 11:25 ` dynamic-hz Andrew Morton
2004-12-13 11:47 ` dynamic-hz Andrea Arcangeli
2004-12-14 3:56 ` dynamic-hz Nish Aravamudan
2004-12-14 3:54 ` dynamic-hz Nish Aravamudan
2004-12-14 4:29 ` dynamic-hz Andrew Morton
2004-12-14 5:25 ` dynamic-hz Nish Aravamudan
2004-12-17 20:10 ` dynamic-hz Nish Aravamudan
2004-12-14 10:01 ` dynamic-hz Domen Puncer
2004-12-14 16:56 ` dynamic-hz Nish Aravamudan
2004-12-14 14:23 ` dynamic-hz linux-os
2004-12-14 16:54 ` dynamic-hz Nish Aravamudan
2004-12-14 17:15 ` dynamic-hz Andrea Arcangeli
2004-12-14 17:42 ` dynamic-hz Nish Aravamudan
2004-12-14 18:29 ` dynamic-hz Andrea Arcangeli
2004-12-14 19:00 ` dynamic-hz Nish Aravamudan
2004-12-14 18:22 ` dynamic-hz linux-os
2004-12-14 18:38 ` dynamic-hz Andrea Arcangeli
2004-12-14 18:50 ` dynamic-hz Pavel Machek
2004-12-13 11:19 ` dynamic-hz Hans Kristian Rosbach
2004-12-13 11:22 ` dynamic-hz Pavel Machek
2004-12-13 11:39 ` dynamic-hz Andrea Arcangeli
2004-12-13 12:51 ` dynamic-hz Hans Kristian Rosbach
2004-12-13 13:01 ` dynamic-hz Andrea Arcangeli
2004-12-13 13:02 ` dynamic-hz Andrea Arcangeli
2004-12-13 15:06 ` dynamic-hz Geert Uytterhoeven
2004-12-13 16:12 ` dynamic-hz Pavel Machek
2004-12-13 16:14 ` dynamic-hz Geert Uytterhoeven
2004-12-14 4:06 ` dynamic-hz Nish Aravamudan
2004-12-14 4:05 ` dynamic-hz Nish Aravamudan
2004-12-13 11:33 ` dynamic-hz Andrea Arcangeli
2004-12-13 14:38 ` dynamic-hz Zwane Mwaikambo
2004-12-13 12:00 ` dynamic-hz Alan Cox
2004-12-13 15:52 ` dynamic-hz Andrea Arcangeli
2004-12-14 22:28 ` dynamic-hz Lee Revell
2004-12-14 22:40 ` dynamic-hz Con Kolivas
2004-12-14 22:50 ` dynamic-hz Lee Revell
2004-12-13 20:26 ` dynamic-hz Olaf Hering
2004-12-13 22:41 ` dynamic-hz Andrea Arcangeli
2004-12-13 20:56 ` dynamic-hz john stultz
2004-12-13 22:21 ` dynamic-hz Andrea Arcangeli
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