From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: george@mvista.com (george anzinger)
Cc: mbs@mc.com (mbs),
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 22:29:03 +0100 (BST) [thread overview]
Message-ID: <E17SlUl-0001ai-00@the-village.bc.nu> (raw)
In-Reply-To: <3D2DE9B2.70A21F7E@mvista.com> from "george anzinger" at Jul 11, 2002 01:25:22 PM
> 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.
Alan
next prev parent reply other threads:[~2002-07-11 21:03 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 ` Alan Cox [this message]
2002-07-11 21:43 ` Periodic clock tick considered harmful (was: Re: HZ, preferably as george anzinger
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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