Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762474AbZANLpG (ORCPT ); Wed, 14 Jan 2009 06:45:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753810AbZANLoo (ORCPT ); Wed, 14 Jan 2009 06:44:44 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:40305 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761799AbZANLon (ORCPT ); Wed, 14 Jan 2009 06:44:43 -0500 Date: Wed, 14 Jan 2009 12:43:47 +0100 From: Ingo Molnar To: Andrew Morton Cc: Joerg Roedel , linux-kernel@vger.kernel.org, mingo@redhat.com, dwmw2@infradead.org, fujita.tomonori@lab.ntt.co.jp, netdev@vger.kernel.org, iommu@lists.linux-foundation.org Subject: Re: [PATCH 03/16] dma-debug: add hash functions for dma_debug_entries Message-ID: <20090114114347.GG8625@elte.hu> References: <1231517970-20288-1-git-send-email-joerg.roedel@amd.com> <1231517970-20288-4-git-send-email-joerg.roedel@amd.com> <20090113005118.82f5037b.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090113005118.82f5037b.akpm@linux-foundation.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: 1.0 X-ELTE-SpamLevel: s X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=1.0 required=5.9 tests=BAYES_50 autolearn=no SpamAssassin version=3.2.3 1.0 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.4796] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1025 Lines: 28 * Andrew Morton wrote: > On Fri, 9 Jan 2009 17:19:17 +0100 Joerg Roedel wrote: > > > +struct hash_bucket { > > + struct list_head list; > > + spinlock_t lock; > > +} ____cacheline_aligned; > > __cacheline_aligned_in_smp. > > This all looks like an exotically large amount of code for a debug > thingy? this code checks the DMA usage of ~1 million lines of kernel code - all the DMA using drivers. I think Joerg's feature is hugely relevant as DMA scribbles are one of the hardest to debug kernel bugs: they can end up in permanent data corruption or other hard to find bugs. In fact i think his patchset is rather simple and even having 10 times as much debug code would pay for its existence in the long run. Ingo -- 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/