linux-kernel - Re: division and cpu usage

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Message-ID: <Pine.LNX.4.64.0708281410230.3018@fbirervta.pbzchgretzou.qr>
Date:	Tue, 28 Aug 2007 14:11:10 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...putergmbh.de>
To:	Luka Napotnik <luka.napotnik@...il.com>
cc:	"linux-os (Dick Johnson)" <linux-os@...logic.com>,
	linux-kernel@...r.kernel.org
Subject: Re: division and cpu usage


On Aug 28 2007 12:41, Luka Napotnik wrote:
>
>How about this:
>===============================
>old_stime = task->stime;
>old_utime = task->utime
>old_j = jiffies;
>
>set_current_state(TASK_INTERRUPTIBLE);
>schedule_timeout(1 * HZ);
>
>new_stime = task->stime;
>new_utime = task->utime;
>new_j = jiffies;
>sum = ((new_stime - old_stime) + (new_utime - old_utime)) * 100 / (new_j
>- old_j)
>===============================
>
>I get how much time the task has spent in 1 sec in the scheduler and
>then get the percentage?

Looks sane to me. Though you have to try. And, like I said before, be aware of
dynticks, so you might want to use something else than jiffies. Not sure what
the function was called though.

	Jan
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