linux-kernel - Re: [RFC -tip] x86, apic: Merge x2apic code

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Date:	Thu, 11 Nov 2010 13:15:52 -0800
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC -tip] x86, apic: Merge x2apic code

On Thu, 2010-11-11 at 12:59 -0800, Cyrill Gorcunov wrote:
> On Thu, Nov 11, 2010 at 12:44:17PM -0800, Suresh Siddha wrote:
> > On Wed, 2010-11-10 at 11:20 -0800, Cyrill Gorcunov wrote:
> > > Hi, while being at x2apic_x.c code I noted that files look similar to
> > > each other so I guessed may be we could merge them. As result --
> > > this patch.
> > 
> > BTW, as you noticed, x2apic cluster mode allows IPI's to be sent to
> > multiple cpu's (in the same cluster) at once. I was hoping sometime I
> > will do this to see if it helps in anything.
> > 
> > So once we do that IPI code will look different.
> 
> yes, indeed, so enlight me a bit -- we have to map every cpu number from
> cpumask to apic-id, then figure out if it belongs to same cluster, collect
> such apic-ids and then send one ipi with one cluster and multiple apic-id
> bits as a destination,

correct.

>  or I miss something and there _can't_ ever be the
> situation when first 16 cpus from cpumask belong to different clusters?

There is no such assumption.

thanks,
suresh

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