linux-kernel - Re: [RFC v1] Tunable sched_mc_power

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Message-ID: <20080630043327.GA6276@dirshya.in.ibm.com>
Date:	Mon, 30 Jun 2008 10:27:37 +0530
From:	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
To:	David Collier-Brown <davecb@....com>
Cc:	Tim Connors <tconnors@...ro.swin.edu.au>,
	Andi Kleen <andi@...stfloor.org>,
	Peter Zijlstra <peterz@...radead.org>, dipankar@...ibm.com,
	balbir@...ux.vnet.ibm.com,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Vatsa <vatsa@...ux.vnet.ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>
Subject: Re: [RFC v1] Tunable sched_mc_power_savings=n

* David Collier-Brown <davecb@....com> [2008-06-29 14:02:58]:

> Andi Kleen <andi@...stfloor.org> said on Fri, 27 Jun 2008 00:38:53 +0200:
>>> Peter Zijlstra wrote:
>>>>> And your workload manager could just nice processes. It should probably
>>>>> do that anyways to tell ondemand you don't need full frequency.
>>>>
>>>> Except that I want my nice 19 distcc processes to utilize as much cpu as
>>>> possible, but just not bother any other stuff I might be doing...
>>>
>>> They already won't do that if you run ondemand and cpufreq. It won't
>>> crank up the frequency for niced processes.
>
>
> Tim Connors then wrote:
>> Shouldn't there be a powernice, just as there is an ionice and a nice?
> Hmmn, how about:
>
> User Commands                                             nice(1)
>
> NAME
>     nice - invoke a command with an altered  priority
>
> SYNOPSIS
>     /usr/bin/nice [-increment | -n increment]  [-s|-i|-e|-p] command  [argu-
>     ment...]
>
> DESCRIPTION
>     The nice utility invokes command, requesting that it be  run
>     with a different  priority.  If -i is specified, the priority
>     of (disk) I/O is modified. If -e is specified, ethernet (or
>     other networking) priority is changed. If -p is specified, power
>     usage priority is changed and if  -s is specified, or none     of -1, 
> -e or -p  is specified, then system scheduling priority
>     is modified...

This is good.  We are exploring powernice.  'Generally' cpu, io and
power nice values should be similar: high or low.  Can we comeup with
use cases where we want to have conflicting nice values for cpu, io
and power?

                CPU     IO      POWER
distcc:         low     low     low
firefox:        low     high    high
ssh/shell:      high    high    high       
X:              high    high    low


I am trying to find answer to the question: Should we have the power
saving tunable as 'nice' value per process or system wide?

How should we interpret the POWER parameter in a datacenter with power
constraint as mentioned in this thread?  Or in a simple case of AC vs
battery in a laptop.

Thanks,
Vaidy

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