From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264265AbUHBWUi (ORCPT ); Mon, 2 Aug 2004 18:20:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264278AbUHBWUi (ORCPT ); Mon, 2 Aug 2004 18:20:38 -0400 Received: from cantor.suse.de ([195.135.220.2]:31878 "EHLO Cantor.suse.de") by vger.kernel.org with ESMTP id S264265AbUHBWUf (ORCPT ); Mon, 2 Aug 2004 18:20:35 -0400 Date: Tue, 3 Aug 2004 00:20:00 +0200 From: Andi Kleen To: Benjamin Herrenschmidt Cc: William Lee Irwin III , Anton Blanchard , sfr@ozlabs.org, linuxppc64-dev , Linux Kernel list , linux-scsi@vger.kernel.org Subject: Re: [PATCH] [ppc64] watch IOMMU virtual merging Message-ID: <20040802222000.GM25951@wotan.suse.de> References: <20040802164448.GN30253@krispykreme> <20040802170843.GI2334@holomorphy.com> <1091483151.7389.78.camel@gaston> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1091483151.7389.78.camel@gaston> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 03, 2004 at 07:45:51AM +1000, Benjamin Herrenschmidt wrote: [adding linux-scsi with full quote] > > Actually, we could tune the ratio between large allocs and small allocs, > the real problem is the failure case. We can't really afford to break > down a physical segment at the iommu level because that would increase > the size of the SG list which can't be dealt at the upper level (we don't > know how much space has been allocated and the HW may have limitations on > the number of entries). > > What we really need is a way for drivers to return the BIO upstream and > ask for a split in case of iommu allocation error, but I've been told that > would be horribly complex... Not very, according to James B. It just needs driver changes. I would like to have it too. -Andi