linux-kernel - Re: RFC: THE OFFLINE SCHEDULER

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Date:	Wed, 26 Aug 2009 17:45:10 +0300
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	raz ben yehuda <raziebe@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Chris Friesen <cfriesen@...tel.com>,
	Mike Galbraith <efault@....de>, riel@...hat.com, mingo@...e.hu,
	andrew motron <akpm@...ux-foundation.org>,
	wiseman@...s.biu.ac.il, lkml <linux-kernel@...r.kernel.org>,
	linux-rt-users@...r.kernel.org
Subject: Re: RFC: THE OFFLINE SCHEDULER

On Wed, 2009-08-26 at 09:47 -0400, Christoph Lameter wrote:
> On Wed, 26 Aug 2009, raz ben yehuda wrote:
> 
> > How will the kernel is going to handle 32 processors machines ?  These
> > numbers are no longer a science-fiction.
> 
> The kernel is already running on 4096 processor machines. Dont worry about
> that.
> 
> > What i am suggesting is merely a different approach of how to handle
> > multiple core systems. instead of thinking in processes, threads and so
> > on i am thinking in services. Why not take  a processor and define this
> > processor to do just firewalling ? encryption ? routing ? transmission ?
> > video processing... and so on...
> 
> I think that is a valuable avenue to explore. What we do so far is
> treating each processor equally. Dedicating a processor has benefits in
> terms of cache hotness and limits OS noise.
> 
> Most of the large processor configurations already partition the system
> using cpusets in order to limit the disturbance by OS processing. A set of
> cpus is used for OS activities and system daemons are put into that set.
> But what can be done is limited because the OS threads as well as
> interrupt and timer processing etc cannot currently be moved. The ideas
> that you are proposing are particularly usedful for applications that
> require low latencies and cannot tolerate OS noise easily (Infiniband MPI
> base jobs f.e.)

My 0.2 cents:

I have always been fascinated by the idea of controlling another cpu
from the main CPU.

Usually these cpus are custom, run proprietary software, and have no
datasheet on their I/O interfaces.

But, being able to turn an ordinary CPU into something like that seems
to be very nice.

For example, It might help with profiling. Think about a program that
can run uninterrupted how much it wants.

I might even be better, if the dedicated CPU would use a predefined
reserved memory range (I wish there was a way to actually lock it to
that range)

On the other hand, I could see this as a jump platform for more
proprietary code, something like that: we use linux in out server
platform, but out "insert buzzword here" network stack pro+ can handle
100% more load that linux does, and it runs on a dedicated core....

In the other words, we might see 'firmwares' that take an entire cpu for
their usage.

> 
> 
> --
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