linux-kernel - Re: [PATCH 2/9] Containers (V9): Example CPU accounting subsystem

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Message-ID: <46377E43.8000605@linux.vnet.ibm.com>
Date:	Tue, 01 May 2007 23:22:03 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	menage@...gle.com
CC:	akpm@...ux-foundation.org, dev@...ru, xemul@...ru,
	serue@...ibm.com, vatsa@...ibm.com, ebiederm@...ssion.com,
	haveblue@...ibm.com, svaidy@...ux.vnet.ibm.com, balbir@...ibm.com,
	pj@....com, ckrm-tech@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, rohitseth@...gle.com,
	mbligh@...gle.com, containers@...ts.osdl.org, devel@...nvz.org
Subject: Re: [PATCH 2/9] Containers (V9): Example CPU accounting subsystem

menage@...gle.com wrote:
> +
> +/* Lazily update the load calculation if necessary. Called with ca locked */
> +static void cpuusage_update(struct cpuacct *ca)
> +{
> +	u64 now = get_jiffies_64();
> +	/* If we're not due for an update, return */
> +	if (ca->next_interval_check > now)
> +		return;
> +
> +	if (ca->next_interval_check <= (now - INTERVAL)) {

These two conditions seem a little confusing.

If ca->next_interval_check > (now - INTERVAL), the else part
is executed, but if ca->next_interval_check > (now - INTERVAL)
then ca->next_interval_check > now, which implies we return
and never enter the else part. It's been quite sometime since
I looked at this code, so I might have gotten it wrong.
I see a load of 0% on my powerpc box. I think it is because
last_interval_time is always 0, I'll debug further


-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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