linux-kernel - Re: [PATCH 0/5] Generic smp_call_function(), improvements, and smp_call_function

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Date:	Thu, 27 Mar 2008 11:43:59 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	linux-kernel@...r.kernel.org, npiggin@...e.de, paulus@...ba.org,
	tglx@...utronix.de, mingo@...hat.com, tony.luck@...el.com,
	Alan.Brunelle@...com
Subject: Re: [PATCH 0/5] Generic smp_call_function(), improvements, and
	smp_call_function_single()

* Jens Axboe <jens.axboe@...cle.com> wrote:

> I very much wanted the kthread approach to work, since it's easier to 
> work with. It's not for lack of will or trying... I'll be happy to 
> supply you otherwise identical patches for this, the only difference 
> being kthread of IPI completions if you want to play with this.

i'd love to be able to run/pull something simple that enables me to 
replicate the measurements you did on a generic PC [without having to 
hit any real IO hardware which would put any context switching effects 
down into the noise category].

Obviously since the kthread approach embedds IPI sending it can never be 
as fast as a pure IPI approach - but it should still be reasonably fast. 
3 usecs versus 2 usecs in a microbenchmark sounds about right to me, but 
it would be better to make it a better-sounding 2.5 usecs versus 2 usecs 
or so :-)

	Ingo
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