From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753937AbYI2I5W (ORCPT ); Mon, 29 Sep 2008 04:57:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752101AbYI2I5O (ORCPT ); Mon, 29 Sep 2008 04:57:14 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:50925 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751802AbYI2I5N (ORCPT ); Mon, 29 Sep 2008 04:57:13 -0400 Date: Mon, 29 Sep 2008 10:56:47 +0200 From: Ingo Molnar To: Joerg Roedel Cc: mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org, fujita.tomonori@lab.ntt.co.jp Subject: Re: [PATCH 3/3] x86/iommu: use __GFP_ZERO instead of memset for GART Message-ID: <20080929085647.GB2190@elte.hu> References: <1222337635-28285-1-git-send-email-joerg.roedel@amd.com> <1222337635-28285-4-git-send-email-joerg.roedel@amd.com> <20080925102012.GA13631@elte.hu> <20080925104212.GA27928@amd.com> <20080927181438.GF1108@elte.hu> <20080927181855.GA11147@elte.hu> <20080928193436.GA8386@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080928193436.GA8386@amd.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Joerg Roedel wrote: > On Sat, Sep 27, 2008 at 08:18:55PM +0200, Ingo Molnar wrote: > > > > another thing: > > > > How hard would it be to add an CONFIG_IOMMU_DEBUG option that forces as > > many DMA requests to go via the IOMMU as possible? > > > > This slows things down of course so it's only for debugging - but it > > also makes sure that we utilize the IOMMU code to the maximum - which is > > not normally the case. > > > > Would be nice to have it .config driven (default-disabled), so that > > -tip's randconfig testing can stumble upon it every now and then. I've > > got GART test-systems - this way we could find certain types of IOMMU > > breakages sooner. > > For AMD IOMMU I disabled the round-robin allocator to stress-test the > code. This means that the address allocation bitmap is always > traversed from the first bit. In consequence the TLB flushing is > stressed a lot (both in hardware and software) because the same DMA > addresses are used again and again. For testing I hardcoded it into > the driver but I can also make it depend on CONFIG_IOMMU_DEBUG. yes - could you please make a new option for it, CONFIG_IOMMU_DEBUG_FORCE=y or so - and cover all iommus that support it? Ingo