From: Pavel Machek <pavel@ucw.cz>
To: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Suresh B Siddha <suresh.b.siddha@intel.com>,
Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>,
Arjan van de Ven <arjan@infradead.org>,
Ingo Molnar <mingo@elte.hu>, Dipankar Sarma <dipankar@in.ibm.com>,
Balbir Singh <balbir@linux.vnet.ibm.com>,
Vatsa <vatsa@linux.vnet.ibm.com>,
Gautham R Shenoy <ego@in.ibm.com>,
Gregory Haskins <gregory.haskins@gmail.com>,
Mike Galbraith <efault@gmx.de>,
Thomas Gleixner <tglx@linutronix.de>,
Arun Bharadwaj <arun@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH v2 0/2] Saving power by cpu evacuation sched_max_capacity_pct=n
Date: Thu, 28 May 2009 22:36:25 +0200 [thread overview]
Message-ID: <20090528203625.GC11477@elf.ucw.cz> (raw)
In-Reply-To: <20090522091457.GY7336@dirshya.in.ibm.com>
Hi!
> > But I don't see why it is neccessary to evacuate cores for this. Why
> > not just schedule special task that enters C3 instead of computing?
>
> This is what essentially happens in the load balancer approach. Not
> scheduling on a particular core will run the scheduler's idle task
> that will transition the core to lowest power state. Pinning a user
> space task and using special driver to hold the core in C3 state will
> break scheduling fairness. At this point the application decides when
> to give the core back to scheduler.
Why would it break scheduling fairness? You just schedule "realtime"
task that does C3 instead of computation. The behaviour is very
similar to "normal" realtime task. Why would it break scheduler?
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
prev parent reply other threads:[~2009-05-28 20:36 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-13 13:11 [RFC PATCH v2 0/2] Saving power by cpu evacuation sched_max_capacity_pct=n Vaidyanathan Srinivasan
2009-05-13 13:11 ` [RFC PATCH v2 1/2] sched: add sched_max_capacity_pct Vaidyanathan Srinivasan
2009-05-13 13:11 ` [RFC PATCH v2 2/2] sched: loadbalancer hacks for forced packing of tasks Vaidyanathan Srinivasan
2009-05-13 13:14 ` [RFC PATCH v2 0/2] Saving power by cpu evacuation sched_max_capacity_pct=n Peter Zijlstra
2009-05-13 13:42 ` [RFC PATCH v2 0/2] Saving power by cpu evacuationsched_max_capacity_pct=n Vaidyanathan Srinivasan
2009-05-13 13:45 ` Balbir Singh
2009-05-13 13:47 ` Peter Zijlstra
2009-05-13 14:42 ` [RFC PATCH v2 0/2] Saving power by cpuevacuationsched_max_capacity_pct=n Balbir Singh
2009-05-13 14:35 ` [RFC PATCH v2 0/2] Saving power by cpu evacuation sched_max_capacity_pct=n Andi Kleen
2009-05-13 14:36 ` Peter Zijlstra
2009-05-13 14:46 ` Andi Kleen
2009-05-13 14:50 ` Peter Zijlstra
2009-05-13 15:01 ` Andi Kleen
2009-05-13 15:02 ` Peter Zijlstra
2009-05-13 15:10 ` Andi Kleen
2009-05-14 14:58 ` Vaidyanathan Srinivasan
2009-05-14 15:06 ` Andi Kleen
2009-05-14 15:43 ` Vaidyanathan Srinivasan
2009-05-14 15:13 ` Vaidyanathan Srinivasan
2009-05-19 20:40 ` Pavel Machek
2009-05-22 9:14 ` Vaidyanathan Srinivasan
2009-05-28 20:36 ` Pavel Machek [this message]
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