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From: Luka Napotnik <luka.napotnik@gmail.com>
To: linux-kernel@vger.kernel.org
Subject: division and cpu usage
Date: Fri, 24 Aug 2007 01:43:30 +0200	[thread overview]
Message-ID: <46CE1BA2.8070200@gmail.com> (raw)

Hello.

I'm new to kernel development and have some questions.

1. Why can't I divide with regular casting to double ((double)a /
(double)b)? It gives me strange errors when compiling:

WARNING: "__divdf3" [/root....] undefined!
WARNING: "__addf3" [/root/...] undefined!
WARNING: "__floatsidf" [/root/...] undefined!

And if I compile with normal integers, I get zero as the result.

2. I'm trying to get the percentage of CPU used for a certain
task_struct and figured the following formula:

(task->utime + task->stime) / jiffies

Before calculating I convert all the variables to jiffies. Is this correct?

Please help.

Greets,
Lukla

             reply	other threads:[~2007-08-23 23:43 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-08-23 23:43 Luka Napotnik [this message]
2007-08-24  1:04 ` division and cpu usage David Schwartz
2007-08-24 11:34 ` linux-os (Dick Johnson)
2007-08-24 12:46   ` Jan Engelhardt
2007-08-25 23:25     ` Luka Napotnik
2007-08-27 22:07     ` Luka Napotnik
2007-08-28  6:45       ` Jan Engelhardt
2007-08-28 10:41         ` Luka Napotnik
2007-08-28 12:11           ` Jan Engelhardt

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