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Subject: Re: [v7 0/8] Reduce cross CPU IPI interference
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Chris Metcalf <cmetcalf@tilera.com>
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Date: Fri, 10 Feb 2012 19:33:36 +0100
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On Thu, 2012-02-02 at 10:41 -0500, Chris Metcalf wrote:
> At Tilera we have been supporting a "dataplane" mode (aka Zero Overhead
> Linux - the marketing name).  This is configured on a per-cpu basis, and in
> addition to setting isolcpus for those nodes, also suppresses various
> things that might otherwise run (soft lockup detection, vmstat work,
> etc.).  

See that's wrong.. it starts being wrong by depending on cpuisol and
goes from there.

> The claim is that you need to specify these kinds of things
> per-core since it's not always possible for the kernel to know that you
> really don't want the scheduler or any other interrupt source to touch the
> core, as opposed to the case where you just happen to have a single process
> scheduled on the core and you don't mind occasional interrupts.

Right, so that claim is proven false I think.

>   But
> there's definitely appeal in having the kernel do it adaptively too,
> particularly if it can be made to work just as well as configuring it
> statically. 

I see no reason why it shouldn't work as well or even better.