Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933564AbYBHGbz (ORCPT ); Fri, 8 Feb 2008 01:31:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752691AbYBHGbr (ORCPT ); Fri, 8 Feb 2008 01:31:47 -0500 Received: from courier.cs.helsinki.fi ([128.214.9.1]:43772 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751387AbYBHGbq (ORCPT ); Fri, 8 Feb 2008 01:31:46 -0500 Message-ID: <47ABF715.60407@cs.helsinki.fi> Date: Fri, 08 Feb 2008 08:30:45 +0200 From: Pekka Enberg User-Agent: Thunderbird 2.0.0.9 (Macintosh/20071031) MIME-Version: 1.0 To: Christoph Lameter CC: Vegard Nossum , Linux Kernel Mailing List , Ingo Molnar , Andi Kleen , Richard Knutsson Subject: Re: [PATCH 1/2] kmemcheck v3 References: <47AB79D4.2070605@gmail.com> <19f34abd0802071412m569e4993kffb4a3af163fa16c@mail.gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1257 Lines: 26 Hi Christoph, Christoph Lameter wrote: > SLABs can be excepted from tracking? Yes. __GFP_NOTRACK can be used to suppress tracking of objects (but we still take the page fault for each access). That is required for things like DMA filled pages that are never initialized by the CPU. SLAB_NOTRACK is for not tracking a whole *cache* so that we _don't_ take the page fault. This is needed for kmemcheck implementation (to avoid recursive page faults for memory accessed by the page fault handler). > So it breaks recursion. But this adds a new cache that is rarely > used. There will be only about 50-100 kmem_cache objects in the system. I > thought you could control the tracking on an per object level? Would not a > kmalloc with __GFP_NOTRACK work? No. We need to not track the whole page to avoid recursive faults. So for kmemcheck we absolutely do need cache_cache but we can, of course, hide that under a alloc_cache() function that only uses the extra cache when CONFIG_KMEMCHECK is enabled? -- 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/