linux-kernel - Re: [PATCH 2/2] x86: implement multiple queues for smp function call IPIs

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Message-ID: <20080730001358.GA23938@one.firstfloor.org>
Date:	Wed, 30 Jul 2008 02:13:58 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Nick Piggin <nickpiggin@...oo.com.au>,
	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] x86: implement multiple queues for smp function call IPIs

On Tue, Jul 29, 2008 at 04:32:57PM -0700, Jeremy Fitzhardinge wrote:
> This adds 8 queues for smp_call_function(), in order to avoid a

Now that we have per CPU IDT and there's no global bottleneck anymore
I think it would be actually fine to use
more than 8 vectors. 32 or 64 might be a better default.

> void native_send_call_func_ipi(cpumask_t mask)
> {
> 	cpumask_t allbutself;
> +	unsigned queue = smp_processor_id() % CONFIG_GENERIC_SMP_QUEUES;

Does this really always run with preemption disabled?

Did I miss it but where is the per vector lock? 

-Andi
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