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From: Pavel Machek <pavel@ucw.cz>
To: Christoph Lameter <clameter@engr.sgi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org, mingo@elte.hu, akpm@osdl.org,
	george@mvista.com, johnstul@us.ibm.com, paulmck@us.ibm.com
Subject: Re: [ANNOUNCE] ktimers subsystem
Date: Wed, 21 Sep 2005 21:24:44 +0200	[thread overview]
Message-ID: <20050921192444.GD467@openzaurus.ucw.cz> (raw)
In-Reply-To: <Pine.LNX.4.62.0509191521400.27238@schroedinger.engr.sgi.com>

Hi!

> > Also the basic prerequisite for for high resolution timers is a fast and
> > simple access to clock_monotonic rather than to a backward corrected
> > clock_realtime representation. 
> 
> Yup that may be a reason to tolerate the add for realtime.
> 
> > We should rather ask glibc people why gettimeofday() / clock_getttime()
> > is called inside the library code all over the place for non obvious
> > reasons.
> 
> You can ask lots of application vendors the same question because its all 
> over lots of user space code. The fact is that gettimeofday() / 
> clock_gettime() efficiency is very critical to the performance of many 
> applications on Linux. That is why the addtion of one add instruction may 
> better be carefully considered. Many platforms can execute gettimeofday 
> without having to enter the kernel.

Eh? One addition is going to be lost in noise compared to syscall overhead.
(For vsyscall, you may be closer to truth, but I doubt it. You could still gain
more than one addition by using some strange calling convention).


-- 
64 bytes from 195.113.31.123: icmp_seq=28 ttl=51 time=448769.1 ms         


  parent reply	other threads:[~2005-09-22 10:32 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-09-19 16:48 [ANNOUNCE] ktimers subsystem tglx
2005-09-19 16:48 ` [PATCH] " tglx
2005-09-19 21:47 ` [ANNOUNCE] " Thomas Gleixner
2005-09-19 22:03 ` Christoph Lameter
2005-09-19 22:17   ` Thomas Gleixner
2005-09-19 22:24     ` Christoph Lameter
2005-09-19 22:44       ` Thomas Gleixner
2005-09-19 22:50         ` john stultz
2005-09-19 22:58           ` Thomas Gleixner
2005-09-19 23:04         ` Christoph Lameter
2005-09-19 23:12           ` Thomas Gleixner
2005-09-20  7:14             ` Ingo Molnar
2005-09-20  7:10       ` Ingo Molnar
2005-09-21 19:24       ` Pavel Machek [this message]
2005-09-19 22:39     ` Christopher Friesen
2005-09-19 22:54       ` Thomas Gleixner
2005-09-20  4:57         ` Christopher Friesen
2005-09-20  5:11           ` Thomas Gleixner
2005-09-20  0:43   ` George Anzinger
2005-09-21 19:50 ` Roman Zippel
2005-09-21 22:41   ` Thomas Gleixner
2005-09-22 12:59     ` Ingo Molnar
2005-09-22 23:09     ` Roman Zippel
2005-09-22 23:31       ` Christopher Friesen
2005-09-23  0:25         ` Roman Zippel
2005-09-23  6:49           ` Thomas Gleixner
2005-09-24  3:15             ` Roman Zippel
2005-09-24  5:16               ` Ingo Molnar
2005-09-24 10:35                 ` Roman Zippel
2005-09-24 13:56                   ` Thomas Gleixner
2005-09-24 16:51                     ` Daniel Walker
2005-09-24 23:45                     ` Roman Zippel
2005-09-25 21:00                       ` Thomas Gleixner
2005-09-27 16:54                         ` Roman Zippel
2005-09-27 19:03                           ` Tim Bird
2005-09-28 16:36                             ` Roman Zippel
2005-09-25 21:02                       ` Thomas Gleixner
2005-09-27 16:48                         ` Roman Zippel
2005-09-27 18:38                           ` Tim Bird
2005-09-27 20:36                             ` George Anzinger
2005-09-23  2:25       ` john stultz
2005-09-23  8:27       ` Thomas Gleixner
2005-09-24  2:43         ` Roman Zippel
2005-09-24  5:03           ` Ingo Molnar
2005-09-24  9:04           ` James Bruce
2005-09-23 15:21       ` Paul E. McKenney
2005-09-24  3:38         ` Roman Zippel
2005-09-25 15:48 Sid Boyce
2005-09-25 18:20 ` Zwane Mwaikambo
2005-09-26  0:02   ` Sid Boyce

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