From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757450AbXKAWie (ORCPT ); Thu, 1 Nov 2007 18:38:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753485AbXKAWi0 (ORCPT ); Thu, 1 Nov 2007 18:38:26 -0400 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:32783 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753055AbXKAWiZ (ORCPT ); Thu, 1 Nov 2007 18:38:25 -0400 Date: Thu, 01 Nov 2007 15:38:24 -0700 (PDT) Message-Id: <20071101.153824.91808126.davem@davemloft.net> To: clameter@sgi.com Cc: akpm@linux-foundation.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, mathieu.desnoyers@polymtl.ca, penberg@cs.helsinki.fi Subject: Re: [patch 0/7] [RFC] SLUB: Improve allocpercpu to reduce per cpu access overhead From: David Miller In-Reply-To: References: <20071101.142936.114015234.davem@davemloft.net> X-Mailer: Mew version 5.2 on Emacs 22.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Christoph Lameter Date: Thu, 1 Nov 2007 15:15:39 -0700 (PDT) > After boot is complete we allow the reduction of the size of the per cpu > areas . Lets say we only need 128k per cpu. Then the remaining pages will > be returned to the page allocator. You don't know how much you will need. I exhausted the limit on sparc64 very late in the boot process when the last few userland services were starting up. And if I subsequently bring up 100,000 IP tunnels, it will exhaust the per-cpu allocation area. You have to make it fully dynamic, there is no way around it.