Subject: Re: 2.6.20-rc6-mm3
From: Daniel Walker <dwalker@mvista.com>
Reply-To: dwalker@mvista.com
To: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>, Andrew Morton <akpm@osdl.org>,
       linux-kernel@vger.kernel.org
In-Reply-To: <20070206214131.GA1176@elte.hu>
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Date: Tue, 06 Feb 2007 13:54:39 -0800
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On Tue, 2007-02-06 at 22:41 +0100, Ingo Molnar wrote:
> * Daniel Walker <dwalker@mvista.com> wrote:
> 
> > > we could make this clearer by renaming 'LOC' (which stands for 
> > > 'LOCal timer interupts' and was added [and misnamed] by yours truly 
> > > many moons ago) to 'apic-timer' and 'timer' to 'PIT-timer' but 
> > > /that/ would be more of a userspace visible change than the change 
> > > in the counter rates.
> > 
> > If we change the current "timer" entry to be listed as "lapic-timer" 
> > and not "IO-APIC-edge" (or one of the other names) and replace it with 
> > the count from LOC , [...]
> 
> doing that would not fake the old behavior (which is your suggestion), 
> LOC is per CPU, while the PIT timer irq that was there is global.
> 
> But, as per the previous mails, the new behavior is just fine, because 
> /proc/interrupts just reflects reality. And the way the kernel utilizes 
> the hardware has just changed - for the better.
> 
> The same happens when say a network driver implements NAPI: the IRQ 
> count goes way, way down. Or if a driver starts supporing MSI - the IRQ 
> line even moves to another one. Do we try to fix those counts up to 
> match the 'previous behavior'? Of course not. What you are suggesting 
> makes no sense, is against current kernel practices - as we pointed it 
> out to you 7 mails ago.

I'm not saying we should "fake" anything .. I'm saying list what's
really happening .. In a human readable way .

Your saying we should keep it unreadable, and let the users be that much
more confused .. Which I don't agree with.

> > [...] that would make sense cause that field already changes depending 
> > if you have a io-apic or not ..
> 
> (that is something else: it's different because a different irq-chip is 
> behind it.)

Why is that not the case with lapic ? 

Daniel

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