linux-kernel - Re: IRQ balancing on a router

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Message-Id: <200810080200.05107.nickpiggin@yahoo.com.au>
Date:	Wed, 8 Oct 2008 02:00:04 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	Jan Kasprzak <kas@...muni.cz>, linux-kernel@...r.kernel.org
Subject: Re: IRQ balancing on a router

On Tuesday 07 October 2008 21:29, Peter Zijlstra wrote:
> On Fri, 2008-10-03 at 06:38 -0700, Arjan van de Ven wrote:
> > The good news is that irqthreads at least have the potential to solve
> > this "lack of information"; if not, we could consider doing a form of
> > microaccounting for irq handlers....
>
> I have some patches floating about that account for nmi/irq/softirq time
> in a fine grained scale. The trouble is that i've so far not found a way
> to handle the case of a jiffie based sched_clock().

Would be nice to have.


> The trouble with that is that time always increases in IRQ context, so
> nmi=0, softirq=0, regular=0 but irq=100%, which is obviuosly
> sub-optimal :-)

Can't you exempt the timer interrupt from counting itself as irq
in the case of timer interrupt based sched_clock()?
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