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Date: Mon, 13 Nov 2006 10:30:51 -0800
From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>, Andi Kleen <ak@suse.de>,
       Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org,
       ashok.raj@intel.com
Subject: Re: [patch] genapic: optimize & fix APIC mode setup
Message-ID: <20061113103051.D17720@unix-os.sc.intel.com>
References: <20061111151414.GA32507@elte.hu> <200611131529.46464.ak@suse.de> <20061113150415.GA20321@elte.hu> <200611131710.13285.ak@suse.de> <20061113163216.GA3480@elte.hu> <20061113100352.C17720@unix-os.sc.intel.com> <20061113184255.GA25528@elte.hu>
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In-Reply-To: <20061113184255.GA25528@elte.hu>; from mingo@elte.hu on Mon, Nov 13, 2006 at 07:42:56PM +0100
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On Mon, Nov 13, 2006 at 07:42:56PM +0100, Ingo Molnar wrote:
> * Siddha, Suresh B <suresh.b.siddha@intel.com> wrote:
> > Not really. That chipset belongs to a MP platform and with your 
> > proposed patch, we will endup using clustered APIC mode and will hit 
> > the issue(in the presence of cpu hotplug) mentioned in that URL.
> 
> hm, why does it end up in clustered mode? Cluster mode should only 
> trigger if the APIC IDs go beyond 16.

go beyond '8' not 16. With Dual-core+HT these MP platforms will have 16 logical
cpus.

> 
> but i'd be fine with never going into cluster mode, instead always using 
> physical flat mode when having more than 8 APICs (independent of the 
> presence of CPU hotplug). On small systems, logical flat mode is what is 
> the best-tested variant (it's also slightly faster).

Ok.

thanks,
suresh