linux-kernel - Re: [PATCH 5/5] x86: update nr

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Message-ID: <4B47A085.1010703@zytor.com>
Date:	Fri, 08 Jan 2010 13:15:49 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] x86: update nr_irqs according cpu num

On 01/08/2010 12:10 PM, Eric W. Biederman wrote:
> 
> I don't know if we ever actually perform vector sharing.  The only case
> I recall where the code could share vectors is if the firmware tables
> told us to irq sources were the same interrupt.  I don't think that
> happens.  We do have the remains of support for vector sharing
> in the code but I don't think it is utilized.  MSI interrupts certainly
> can not share vectors.
> 

We probably will need to support that at some point, though, simply
because it's not all that hard to construct a system in which there are
more MSI-X interrupts than there are possible vectors in the system.

Until then we can do 224 * nr_cpus_ids, but it's still not the right thing.

> Yes.  It was enough of a pain the first pass at it that we wound
> up with nr_irqs, a value that can vary at boot time.
> 
> Once YH's radix tree changes get it in.  A war on NR_IRQS and nr_irqs
> seems appropriate.

Agreed.

	-hpa

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