From: george anzinger <george@mvista.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: mbs <mbs@mc.com>,
dank@kegel.com,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Periodic clock tick considered harmful (was: Re: HZ, preferably as
Date: Thu, 11 Jul 2002 14:43:36 -0700 [thread overview]
Message-ID: <3D2DFC08.445B2723@mvista.com> (raw)
In-Reply-To: E17SlUl-0001ai-00@the-village.bc.nu
Alan Cox wrote:
>
> > First blush is HELL YES! The issue is accounting. When you
> > ask how long a program ran, you are looking at the
> > accounting that happens on a tick. This is where one of two
>
> Thats also an implementation issue. Note that the current code is also
> wildly inaccurate. Mr Shannon says we are good to at best 50 run/sleep
> changes a second. I've got "100% busy" workloads that are 99% asleep.
>
> Tracking cpu usage at task switch works a lot better for newer processors
> which as well as having rdtsc also have performance counters. In fact you
> can do much more interesting things on modern PC class platforms like
> scheduling using pre-emption interrupts based on instructions executed,
> memory accesses and more.
>
Oh, I agree. Hardware could make all this a lot easier.
--
George Anzinger george@mvista.com
High-res-timers:
http://sourceforge.net/projects/high-res-timers/
Real time sched: http://sourceforge.net/projects/rtsched/
Preemption patch:
http://www.kernel.org/pub/linux/kernel/people/rml
next prev parent reply other threads:[~2002-07-11 21:41 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-11 16:44 Periodic clock tick considered harmful (was: Re: HZ, preferably as small as possible) dank
2002-07-11 16:59 ` Thunder from the hill
2002-07-11 19:45 ` Arnd Bergmann
2002-07-11 17:05 ` Hubertus Franke
2002-07-11 19:06 ` george anzinger
2002-07-11 19:19 ` mbs
2002-07-11 20:25 ` george anzinger
2002-07-11 21:29 ` Periodic clock tick considered harmful (was: Re: HZ, preferably as Alan Cox
2002-07-11 21:43 ` george anzinger [this message]
2002-07-11 22:32 ` Periodic clock tick considered harmful (was: Re: HZ, preferably as small as possible) Karim Yaghmour
2002-07-15 5:21 ` Linus Torvalds
2002-07-15 5:43 ` Linus Torvalds
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