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Subject: Re: No 100 HZ timer !
To: ak@suse.de (Andi Kleen)
Date: Tue, 10 Apr 2001 12:18:03 +0100 (BST)
Cc: mbs@mc.com (Mark Salisbury), jdike@karaya.com (Jeff Dike),
        schwidefsky@de.ibm.com, linux-kernel@vger.kernel.org
In-Reply-To: <20010410075109.A9549@gruyere.muc.suse.de> from "Andi Kleen" at Apr 10, 2001 07:51:09 AM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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> > interrupting decrementer.  (i.e just about any modern chip)
> 
> Just how would you do kernel/user CPU time accounting then ?  It's currently done 
> on every timer tick, and doing it less often would make it useless.

On the contrary doing it less often but at the right time massively improves
its accuracy. You do it on reschedule. An rdtsc instruction is cheap and all
of a sudden you have nearly cycle accurate accounting

Alan

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