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From: Simon Klinkert <simon.klinkert@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>, Mike Galbraith <efault@gmx.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	mingo@redhat.com, Trond.Myklebust@netapp.com
Subject: Re: Meaningless load?
Date: Thu, 11 Oct 2012 09:19:49 +0200	[thread overview]
Message-ID: <8CCB73B0-34AD-47E2-9379-DB6F02DB35F5@gmail.com> (raw)
In-Reply-To: <1349886164.1279.20.camel@twins>


On 10.10.2012, at 18:22, Peter Zijlstra  wrote:

> On Wed, 2012-10-10 at 17:44 +0200, Simon Klinkert wrote:
>> I'm just wondering if the 'load' is really meaningful in this
>> scenario. The machine is the whole time fully responsive and looks
>> fine to me but maybe I didn't understand correctly what the load
>> should mean. Is there any sensible interpretation of the load?
> 
> I'll leave meaningful aside, but uninterruptible (D state) is part of
> how the load thing is defined, so your 500 result is correct.

Yes, the calculation of the load is correct but I still don't know how I should interpret the load…

On 11.10.2012, at 06:02, Mike Galbraith wrote:

> Makes perfect sense to me.  Work _is_ stack this high.  We don't and
> can't know whether the mountain is made of popcorn balls or boulders.

That's the point. Afaik the D state never represents 'work'. These processes are waiting for something.

Let's say we have 10,000 processes in the D state (and thus a load of ~10,000) doing nothing. What should the load tell me? The machine is under fire? There is nothing to do? There might be something to do but the machine doesn't know?

Simon



  reply	other threads:[~2012-10-11  7:19 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-10 15:44 Simon Klinkert
2012-10-10 16:22 ` Peter Zijlstra
2012-10-11  7:19   ` Simon Klinkert [this message]
2012-10-11  8:13     ` Mike Galbraith
2012-10-11 13:17       ` Simon Klinkert

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