From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S932514AbbI3RoJ (ORCPT <rfc822;w@1wt.eu>);
	Wed, 30 Sep 2015 13:44:09 -0400
Received: from www.linutronix.de ([62.245.132.108]:41800 "EHLO
	Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753956AbbI3RoI (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Wed, 30 Sep 2015 13:44:08 -0400
Date: Wed, 30 Sep 2015 19:43:23 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Denys Vlasenko <dvlasenk@redhat.com>
cc: Ingo Molnar <mingo@kernel.org>, Jiang Liu <jiang.liu@linux.intel.com>,
        Len Brown <len.brown@intel.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC] x86: Reduce MAX_LOCAL_APIC and MAX_IO_APICS
In-Reply-To: <560C0479.2080602@redhat.com>
Message-ID: <alpine.DEB.2.11.1509301941370.4500@nanos>
References: <1443210512-24236-1-git-send-email-dvlasenk@redhat.com> <alpine.DEB.2.11.1509301709220.4500@nanos> <560C0479.2080602@redhat.com>
User-Agent: Alpine 2.11 (DEB 23 2013-08-11)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
X-Linutronix-Spam-Score: -1.0
X-Linutronix-Spam-Level: -
X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required,  ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, 30 Sep 2015, Denys Vlasenko wrote:
> On 09/30/2015 05:11 PM, Thomas Gleixner wrote:
> > On Fri, 25 Sep 2015, Denys Vlasenko wrote:
> >>  
> >> +config MAX_LAPIC_ID
> >> +	int "Maximum APIC ID"
> >> +	range 8 32768
> >> +	default "8"
> >> +	---help---
> >> +	  Use this option to set maximum allowed Local APIC ID higher than
> >> +	  maximum number of CPUs. This may be necessary for machines
> >> +	  with large number of processor sockets and non-contiguous
> >> +	  LAPIC numbering.
> >> +	  This setting will be automatically rounded up, if necessary.
> > 
> > This is wrong. If you would limit the APIC IDs then you really break
> > stuff. You can only limit the number of APICs.
> 
> This CONFIG setting allows to _increase_ max APIC ID.

NO. This is crap. I don't want to tweak a gazillion of knobs just to
build a kernel with CONFIG_NR_CPUS=8. Really not.

If you really want to make that space saving, then make it a runtime
allocation.
 
Thanks,

	tglx