From mboxrd@z Thu Jan  1 00:00:00 1970
Subject: Re: [Xenomai-core] Nocow patch.
From: Philippe Gerum <rpm@xenomai.org>
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Date: Fri, 19 Jan 2007 10:58:53 +0100
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To: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Cc: xenomai-core <xenomai@xenomai.org>

On Fri, 2007-01-19 at 10:22 +0100, Gilles Chanteperdrix wrote:
> Gilles Chanteperdrix wrote:
> > However, after looking at the ARM patch, I am not so sure
> > __ipipe_update_all_pinned_mm() is the way to go on all architectures.
> > The ARM I-pipe handles vmalloc and ioremap faults without causing a mode
> > switch, I wonder if it is not better than having
> > __ipipe_update_all_pinned_mm() updating page directories all over the
> > place.
> 
> I checked with the I-pipe tracer the overhead on an ARM of a fault on a
> vmalloced area: it costs around 5 us.
> 

What is the average latency in user-space on this board for 1Khz and
10Khz periods?

Beyond that, we may want to keep both approaches at hand in the core
infrastructure; running the same benchmark on, say an integrator, may
give much higher latencies due to lousy cache issues. This still needs
to be verified though.

-- 
Philippe.