linux-kernel - Re: [PATCH 1/3] clockevents: Use an atomic RCU notifier for clockevents

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Message-ID: <alpine.LFD.2.02.1109070113090.2723@ionos>
Date:	Wed, 7 Sep 2011 01:19:06 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andi Kleen <ak@...ux.intel.com>
cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] clockevents: Use an atomic RCU notifier for
 clockevents

On Tue, 6 Sep 2011, Andi Kleen wrote:

> > The idle code, at least the one in drivers/idle/intel_idle.c, does
> > _NOT_ call into that code at all when a reliable lapic timer is
> > available:
> 
> But the ACPI idle doesn't check that, so it still has a scalability problem.
> 
> Hmm ok so could add that check into acpi idle too I guess, but then ACPI
> idle doesn't normally know anything about CPUs.
> 
> > Either you are using different code or your machine does not have that
> > ARAT flag set.
> 
> The second test was using ACPI idle.

And as I said in that very same mail:

> > Same applies for drivers/acpi/processor_idle.c

lapic_timer_check_state()
{
       if (cpu_has(&cpu_data(pr->id), X86_FEATURE_ARAT))
                return;
....

WTF are you talking about? 

Thanks,

	tglx
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