From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932241AbYFFVvs (ORCPT ); Fri, 6 Jun 2008 17:51:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933501AbYFFVvd (ORCPT ); Fri, 6 Jun 2008 17:51:33 -0400 Received: from smtp-out.google.com ([216.239.33.17]:53314 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933487AbYFFVvb (ORCPT ); Fri, 6 Jun 2008 17:51:31 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=received:message-id:date:from:to:subject:cc:in-reply-to: mime-version:content-type:content-transfer-encoding: content-disposition:references; b=WydEqrqf2yBa7BzBFANkHjopub3kbk6D/ZISDYoClf9PMUOhrKPAjdbX8u5heLAPd j0S+hGOHjQ+id+8qV7Z/A== Message-ID: Date: Fri, 6 Jun 2008 14:51:17 -0700 From: "Grant Grundler" To: "Muli Ben-Yehuda" Subject: Re: Intel IOMMU (and IOMMU for Virtualization) performances Cc: "FUJITA Tomonori" , linux-kernel@vger.kernel.org, mgross@linux.intel.com, linux-scsi@vger.kernel.org In-Reply-To: <20080606213659.GC15085@il.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080604235053K.fujita.tomonori@lab.ntt.co.jp> <20080606202119.GQ15085@il.ibm.com> <20080606213659.GC15085@il.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 6, 2008 at 2:36 PM, Muli Ben-Yehuda wrote: ... > The logic seems pretty simple to me, all we need to do is keep track > of how many entries are currently allocated in the bitmap vs. the size > of the bitmap. Once we get to the half-way point, double the size of > the bitmap. "half-full" would be one hueristic but others might be more suitable (e.g. wait until it's nearly full or bitmap search fails). > Having said that, I'm not sure it's worth it, and have no > plans to implement it :-) The historical DMA mapping "failure mode" is a kernel panic. Resizing or creating a new IOMMU page table would avoid a panic, my guess is people would prefer _anything_ that avoids a panic. :) Especially in the context of Virtual Machines and multiply guests. And I'm not exposed to this problem (yet)...I expect Mark Gross (Intel) is on the hook for this and has access to all the documentation. I'll let him thank you for suggesting more work. :P thanks, grant