Message-ID: <4AC374E3.9000308@openvz.org>
Date: Wed, 30 Sep 2009 19:10:27 +0400
From: Pavel Emelyanov <xemul@openvz.org>
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To: balbir@linux.vnet.ibm.com
CC: bharata@linux.vnet.ibm.com, linux-kernel@vger.kernel.org,
       Dhaval Giani <dhaval@linux.vnet.ibm.com>,
       Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>,
       Gautham R Shenoy <ego@in.ibm.com>,
       Srivatsa Vaddagiri <vatsa@in.ibm.com>, Ingo Molnar <mingo@elte.hu>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Herbert Poetzl <herbert@13thfloor.at>, Avi Kivity <avi@redhat.com>,
       Chris Friesen <cfriesen@nortel.com>, Paul Menage <menage@google.com>,
       Mike Waychison <mikew@google.com>
Subject: Re: [RFC v2 PATCH 0/8] CFS Hard limits - v2
References: <20090930124919.GA19951@in.ibm.com> <4AC35EDD.1080902@openvz.org> <20090930143820.GG3071@balbir.in.ibm.com>
In-Reply-To: <20090930143820.GG3071@balbir.in.ibm.com>
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Balbir Singh wrote:
> * Pavel Emelyanov <xemul@openvz.org> [2009-09-30 17:36:29]:
> 
>> Bharata B Rao wrote:
>>> Hi,
>>>
>>> Here is the v2 post of hard limits feature for CFS group scheduler. This
>>> RFC post mainly adds runtime borrowing feature and has a new locking scheme
>>> to protect CFS runtime related fields.
>>>
>>> It would be nice to have some comments on this set!
>> I have a question I'd like to ask before diving into the code.
>> Consider I'm a user, that has a 4CPUs box 2GHz each and I'd like
>> to create a container with 2CPUs 1GHz each. Can I achieve this
>> after your patches?
> 
> I don't think the GHz makes any sense, consider CPUs with frequency
> scaling. If I can scale from 1.6GHz to say 2.6GHz or 2GHz to 4GHz,
> what does it mean for hard limit control? Hard limits define control
> over existing bandwidth, anything else would be superficial and hard
> hard to get right for both developers and users.

Two numbers for configuring limits make even less sense OTOH ;)
By assigning 2GHz for 4GHz CPU I obviously want half of its power ;)
Please, see my reply to vatsa@ in this thread.
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