linux-kernel - Re: [RFC PATCH 00/10] Alpha support for QEMU

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Message-ID: <20130719100330.GA20339@stolen.phys.waikato.ac.nz>
Date:	Fri, 19 Jul 2013 22:03:30 +1200
From:	Michael Cree <cree@...kato.ac.nz>
To:	Richard Henderson <rth@...ddle.net>
Cc:	linux-kernel@...r.kernel.org, ink@...assic.park.msu.ru,
	mattst88@...il.com, linux-alpha@...r.kernel.org
Subject: Re: [RFC PATCH 00/10] Alpha support for QEMU

On Thu, Jul 18, 2013 at 03:04:25PM -0700, Richard Henderson wrote:
> On 07/18/2013 02:28 PM, Michael Cree wrote:
> > On the kernel without the patch set the dummy-RTC timer interrupt received
> > 30876 interrupts in a 30s period which is within measurement uncertainty of
> > the expected 30*1024 = 30720 interrupts.
> > 
> > On the kernel with the patch set the dummy-RTC timer interrupt received 14419 
> > interrupts on CPU-1, 13935 interrupts on CPU-2 and 2619 interrupts on CPU-3
> > over a 30s period.
> 
> Grr.  Naturally, the old kernel obfuscates which timers are being delivered
> where.  So a direct comparison doesn't appear possible.  But those separated
> numbers seem uncomfortably low.
> 
> I've just pushed a new branch to
> 
>   git://github.com/rth7680/linux.git axp-qemu-7
> 
> Please try that with CONFIG_ALPHA_WTINT disabled.  I'd like to eliminate that
> as a source of uncertainty for your system.

Running that axp-qemu-7 branch with RTC_DRV_ALPHA on and ALPHA_WTINT off
still results in a rather slow clock.  (Does start up with correct time
now that I have RTC_DRV_ALPHA selected.)

Over a 30s period still get too few timer interrupts: 843, 28805 and 1434
interrupts on the CPUs.

Cheers
Michael
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