linux-kernel - Re: [PATCH 1/2] Add scaled time to taskstats based process accounting

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Message-ID: <13853.1187326604@neuling.org>
Date:	Fri, 17 Aug 2007 14:56:44 +1000
From:	Michael Neuling <mikey@...ling.org>
To:	balbir@...ux.vnet.ibm.com
cc:	Paul Mackerras <paulus@...ba.org>, Andrew Morton <akpm@...l.org>,
	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH 1/2] Add scaled time to taskstats based process accounting 

In message <46C52872.9060408@...ux.vnet.ibm.com> you wrote:
> Michael Neuling wrote:
> >> I'd also request for you to add a cpu_scaled_run_real_total for use
> >> by delay accounting. cpu_scaled_run_real_total should be similar in
> >> functionality to cpu_run_real_total.
> > 
> > Will do.  Should I add cpu_scaled_run_real_total to the end of the
> > struct taskstat, or next to cpu_run_real_total?
> > 
> 
> Please add it to the end, that helps maintain binary compatibility
> across all versions of taskstats.

OK

> 
> >>>  	/* Note: this timer irq context must be accounted for as well. */
> >>> -	if (user_tick)
> >>> +	if (user_tick) {
> >>>  		account_user_time(p, jiffies_to_cputime(1));
> >>> -	else
> >>> +		account_user_time_scaled(p, jiffies_to_cputime(1));
> >>> +	} else {
> >>>  		account_system_time(p, HARDIRQ_OFFSET, jiffies_to_cputime(1));
> >>> +		account_system_time_scaled(p, jiffies_to_cputime(1));
> >>> +	}
> >> I am a little confused here, scaled accounting and regular accounting
> >> go hand in hand?
> > 
> > We need to account for scaled and normal time in this generic code.
> > All other calls to account_(user|system)_time are in arch code.  
> > 
> 
> So the assumption here is that we ran at full frequency during
> this time, is my understanding correct?

Yes.  

I guess we could keep a per CPU last scaling factor for this case
(similar to what we are storing in the POWERPC paca)

Mikey
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