Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757721AbXFLCMQ (ORCPT ); Mon, 11 Jun 2007 22:12:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754518AbXFLCMD (ORCPT ); Mon, 11 Jun 2007 22:12:03 -0400 Received: from mga02.intel.com ([134.134.136.20]:44027 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754381AbXFLCMB (ORCPT ); Mon, 11 Jun 2007 22:12:01 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.16,409,1175497200"; d="scan'208";a="253309545" Date: Mon, 11 Jun 2007 19:08:06 -0700 From: "Siddha, Suresh B" To: Arjan van de Ven Cc: Andrew Morton , "Keshavamurthy, Anil S" , Andi Kleen , Christoph Lameter , linux-kernel@vger.kernel.org, gregkh@suse.de, muli@il.ibm.com, asit.k.mallick@intel.com, suresh.b.siddha@intel.com, ashok.raj@intel.com, shaohua.li@intel.com, davem@davemloft.net Subject: Re: [Intel-IOMMU 02/10] Library routine for pre-allocat pool handling Message-ID: <20070612020806.GA17143@linux-os.sc.intel.com> References: <200706090056.49279.ak@suse.de> <200706091147.24705.ak@suse.de> <20070611204442.GA4074@linux-os.sc.intel.com> <20070611141449.bfbc4769.akpm@linux-foundation.org> <20070611235208.GC25022@linux-os.sc.intel.com> <20070611173001.e0355af3.akpm@linux-foundation.org> <466DF290.2040503@linux.intel.com> <20070611183555.fe763fe4.akpm@linux-foundation.org> <466DFD22.5080303@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <466DFD22.5080303@linux.intel.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1484 Lines: 34 On Mon, Jun 11, 2007 at 06:55:46PM -0700, Arjan van de Ven wrote: > Andrew Morton wrote: > >On Mon, 11 Jun 2007 18:10:40 -0700 Arjan van de Ven > > wrote: > > > >>Andrew Morton wrote: > >>>>Where as resource pool is exactly opposite of mempool, where each > >>>>time it looks for an object in the pool and if it exist then we > >>>>return that object else we try to get the memory for OS while > >>>>scheduling the work to grow the pool objects. In fact, the work > >>>>is schedule to grow the pool when the low threshold point is hit. > >>>I realise all that. But I'd have thought that the mempool approach is > >>>actually better: use the page allocator and only deplete your reserve > >>>pool > >>>when the page allocator fails. > >>the problem with that is that if anything downstream from the iommu > >>layer ALSO needs memory, we've now eaten up the last free page and > >>things go splat. > > > >If that happens, we still have the mempool reserve to fall back to. > > we do, except that we just ate the memory the downstream code would > use and get ... so THAT can't get any. Then this problem can happen, irrespective of the changes we are reviewing in this patch set. Is n't it? thanks, suresh - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/